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Wednesday, October 21, 2009

Paradise Flycatcher Conservation Project – breaking news…

Rachel Bristol (Project Officer under the Seychelles Paradise Flycatcher project) visited Denis last week to catch up on the Flycatcher population there and their status. On her return she was able to report some excellent progress including the commencement of breeding activities for the new season and some early successes, Rachel Continues below:

“After a few months break the flycatchers on Denis have started breeding in force again. Flycatchers can breed year–round but there is a marked peak in breeding during the North-West or rainy season from November- April. However, the dry South-East season this year has been considerably wetter than usual which likely explains the early start to the breeding season.

I was on Denis last week and of 8 potentially breeding pairs six of them are currently active. We have 2 new fledglings that fledged two weeks ago and yesterday (19 October 09) respectively, a nestling just hatched yesterday and 2 further pairs are nest building. A 6th pair has a dependant juvenile that fledged in August.


Now almost 11 months since the Conservation Introduction of 23 flycatchers to Denis we are beginning to get an idea of how successful the introduction will be. The current population is 24 individuals; we have lost 4 of the original introduced stock but have had 5 chicks fledge on Denis. After a shaky start where the majority of nesting attempts were failing (due to a combination of eggs failing to hatch and de-predation of both eggs and nestlings- [ed: most likely by Mynah Birds a problem which still requires redress]) the flycatchers appear to be “getting it together” and successfully breeding on Denis- the key to establishment of a self-sustaining population.”

This really is fantastic news – the Flycatcher transfer to Denis in November of last year was the first ever transfer of this critically endangered species and constitutes a key step in securing the future of this beautiful and iconic endemic species.

This success is largely down to the tireless efforts of Rachel over the previous three years. Rachel is currently working to complete her PhD thesis on the species and we wish her all the best in her ongoing endeavours.

While she was on Denis Rachel took the opportunity to measure and ring a flycatcher nestling and has kindly sent us some great photos of the young bird see photos in sidebar.

The Seychelles Paradise Flycatcher Project is a multi-partner undertaking funded by the Darwin Initiative and supported by partners including Nature Seychelles, the University of Kent, the La Digue Development Board, Denis Island and the DoE.

Friday, October 2, 2009

All creatures great and small…

It has indeed been a considerable time since I last visited Denis as a confluence of events and paperwork deadlines have kept me “trapped” on the main island of Mahe. This has in turn meant a marked decrease in my posts from an average of 8 posts a month through July to just 2 and 1 in August and September respectively.

This, by chance, has meant that visitors to the blog of late have been greeted upfront by photos of the Seychelles skink and a couple of species of crab – perhaps not everyone’s cup of tea or idealised perception of an idyllic tropical island. At this point it is timely for me to state that Denis is very much the epitome of a picture postcard tropical island and I am certain will meet the requirements of such from its visitors.

The spectre of brown lizards and hairy-legged crabs has however been visited upon me today by a member of the island’s marketing section concerned that the perception generated is inappropriate. Perception is of course - in these modern times of multi-media, sound bites, 24-hour news and spin-laden politics - increasingly everything with substance coming often at best second.

Lizards and crabs play a vital role in the island’s ecosystem breaking down detritus and recycling nutrients. It is imperative in the management of fragile islands that a comprehensive ecosystem approach to environment is utilised and that all native species, regardless of aesthetic appeal, are incorporated therein. Without one there is often not the other as each contributes to the health of the whole.

However, visitors to this blog and prospective visitors to Denis Island can rest assured that they will find yearnings for both perception and substance satisfied in the environmental management of the island. That is not to say all is perfect, the rehabilitation and restoration of the island’s ecosystem is a long term process but great steps have been made.

The key alien predators, cats and rats, were removed in 2000 and 2002 respectively. This coupled with extensive habitat rehabilitation paved the way for the introduction of rare and threatened species such as the Seychelles warbler, Seychelles fody, the endangered Seychelles magpie-robin and the first ever transfer of the critically endangered Seychelles paradise flycatcher.

Thankfully from a marketing perspective these birds are also pretty… see photos in sidebar.

Meanwhile the work continues on all creatures great and small.

Wednesday, September 2, 2009

The Seychelles Skink (Mabuya sechellensis)

A common sight on the ground in the woodlands of Denis, and indeed throughout the central Seychelles archipelago is the Seychelles skink (Mabuya sechellensis). This species is endemic to the central Seychelles.

On Denis this coppery-brown lizard gets up to approximately 22-23cm in length – including its tail. It has a distinct pale stripe running from above the eye down the top of each flank fading out at the tail. This stripe is emphasised by rows of darker patches running above and below it (see photos). This pale stripe and the pale belly in turn make the flanks appear as a brown stripe. The striping varies in prominence from island to island with adults in some populations reportedly not having stripes.

On some islands the skink can reach very high densities (e.g. Cousin) but this is not the case here. On Denis one generally first notices a skink by a rustle in the undergrowth as it seeks to avoid our great marauding feet! The best way to observe them I have found is by moving off the paths into areas of broadleaved woodland and just finding a comfortable perch. Once still, one rapidly becomes aware of the movement of the skinks across the forest floor and they often approach as curiosity brings them in search of food.

Gerlach (2007) states that the skink has been introduced to Denis and some credence is provided to this idea by the fact that no skinks were recorded on Denis’ nearest neighbour Bird in 1908 (Fryer 1910) but were subsequently found in 1939 – a timeframe highly suggestive of a human vector. For Denis though it is not so conclusive. Skinks were recorded in 1908 and it is definitely possible that they could have arrived on Denis during its 14,000 year history through natural means – i.e. “rafting” on floating vegetation.

Regardless the skink, as a species endemic to the central archipelago, is treated as native species and serves an important role in the ecosystem feeding omnivorously on insects, fruit, detritus and carrion. Skinks also provide a source of food for moorhens and interestingly the endangered magpie-robin which is highly adept at swooping down on an unsuspecting young lizard and despatching it clinically by 2 or 3 hard “thwacks” against a stone before consuming it.

The skinks lay 2 or more oblong, leathery white eggs and cover them with soil. We do anticipate that as sea bird colonies increase on the island that the detritus they bring – small fish, droppings, eggs and dead birds – will see a corresponding increase in the skink population.

Refs:
Fryer, J.C.F. (1910). Bird and Denis Islands, Seychelles. Trans. Linn. Soc. Land. (2)14: 15-20.
Gerlach, J. (2007). Terrestrial and Freshwater Vertebrates of the Seychelles Islands. Backhuys Publishers. The Netherlands.

Friday, August 28, 2009

Catching-up…

Leave and then the frantic writing of a project proposal to meet the donor deadline have kept me from posting for nearly a month and away from the island for longer, so just a few quick bullets to bring the blog up to date:
  • Great news from Rachel, we have now our third successful fledging of a Seychelles paradise flycatcher on the island which is most encouraging. Breeding activity has now ceased as is usual for this time of year.
  • Vicki and Georgia headed home at the end of July. Their work on the Sooty tern project was very fruitful with numerous landings recorded and very encouraging behaviour displayed. We believe that the birds that visited the island this year are young adults that have not previously bred reconnoitring potential breeding sites for the future. If so this is indeed a very encouraging development. I look forward to receiving the write-ups of their work and also hopefully they will contribute a post or two to the blog.
  • Jildou and Peter have finished their work on the warblers (Acrocephalus sechellensis) on Denis for this visit and dropped by to the office last week to update me on their findings. They were able to catch and ring 99 birds during their stay and estimate that the island population is about 150 - 175 birds. There are now approximately 75 territories on the island. Once independent, young birds leave their natal territories. There are therefore a certain number of birds “floating”. That is to say moving round the island looking for a territory of their own. On Cousin Island where the warbler population is at carrying capacity the birds exhibit cooperative breeding where the young, and particularly the females, often remain in their natal territory and help their parents raise the next generation of siblings. This different life tactic is utilised because the entire existing habitat is occupied and the bird’s evolutionary fitness is optimised by helping to raise its siblings and seeking over time to either inherit the territory or gradually establish a territory off the side of the existing one. The high proportion of unringed birds found in the population during this visit is evidence of ample successful breeding but also suggests a quite high rate of adult mortality. Of particular concern is that Jildou and Peter estimate that 1 in 5 of the adults shows evidence of scarring and injury around the head. Such injuries are not evident on the other island populations and once again suspicion points to the predatory impact of the invasive Mynah bird.

I don’t know when I will be going back to the island, but I do have a backlog of a few things I could post on so I will try and post a couple of times over the next week. Keep checking back for updates…

Monday, August 3, 2009

More on littoral crabs... new records for Denis Island.

I posted at length on the 5th of July on the Sally lightfoot crab (Grapsus tenuicrustatus) and was able to get a few good shots of the animals as waves broke over them. G. tenuicrustatus is a common sight on the sandstone formations to be found around the southern and eastern coastline of the island and is indeed the only rocky shore crab previous studies have recorded on the island. I was very interested therefore to find other species present in the southern rocks when I was trying to get photos of G. tenuicrustatus. They were much more shy than the “Lightfoots” and difficult to photo but I was able to get a few snaps sufficient for their identification.

Eriphia smithirough red-eyed crab, red-eyed reef crab, pebble crab

E. smithi has an indo-pacific distribution and is reportedly very common on east African coasts. It has various distinctive characteristics which when combined allow for species identification. Most apparent are the bright red eyes on white stalks and this immediately narrows down its identity, this coupled with the numerous spines on carapace edge behind the eyes and the large molariform tooth on the larger claw clearly identify it as E. smithi.

This is an interesting species that grazes on algae during the day but turns predator of crustaceans and molluscs at night. At low tide at night individuals have been reported to roam out up to 50m on to reef flats in search of prey before returning to their crevice hideouts (Vaninni et al 1989). Rock crevices play an important part in their lifecycle for seclusion and mating and individual crabs can remain loyal to a single retreat for 3 weeks or more. The southern reaches of the island seem ideal in this regard with numerous cracks and crevices in the sandstone and large reef flats that are exposed at low tide.

Geograpsus stormi – red nipper.

Now I can’t be sure of this identification as I do not yet have a full dorsal photo of this crab (it moved very rapidly and agilely over the rocks in its search of refuge) but judging from the colour of its legs and eyes and the presence of prominent long bristles on the legs I am fairly certain that it is a specimen of the rocky shore crab G. stormi .

G. stormi has a western Indian ocean to central pacific distribution (Richmond 1997) and has been noted for its consumption of rocky shore carrion. Interestingly Haig (1984) records G. stormi as only occurring on islands that fit the habitat category of “low islands with mangroves” - in this case citing the outer island atolls of Aldabra and Cosmoledo. She does however go on to note that it is likely that G. stormi (inter alia) will be found on islands without mangroves as more “collecting” is done.

References:
1). Cook Islands biodiversity Database
(2009). http://cookislands.bishopmuseum.org/species.asp?id=7351
2). Haig, J. (1984). Land and freshwater crabs of the Seychelles and neighbouring islands. In: Stoddardt, D.R. Biogeography and ecology of the Seychelles islands. Junk Publishers, The Hague.
3). Richmond, M.D. (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean Islands. ISBN 91-630-4594-X.
4).Vaninni, M. et al (1989). Feeding habits of the pebble crab Erithia smithi. Marine Biology 100, (249 -252) 1989.

Friday, July 24, 2009

Nature Notes & Bird Bulletin…

I am taking some leave in the coming weeks so posts will likely be scarce for a good few weeks. I will use this combined “Nature Notes & Bird Bulletin” post to summarise a few odds and ends from my last island visit.

Nature Notes

Magpie Robin News. We have experienced some considerable set-backs in recent months with several chicks lost to Mynah bird attacks and two adults lost to illness. This is a matter of real concern as the population has decreased to 20 birds which is the number we started with a year ago and we have lost more females than males from the adult population. It is urgent that we take measures to improve breeding success in the population. The estate has been assisting with localised habitat management creating higher quality feeding grounds in each territory. Meanwhile I am in final negotiations with the island under what conditions we can bring a marksman to the island to undertake a preliminary cull of the Indian mynah population. The Indian mynah (Acridotheres tristis) is an invasive alien species in Seychelles and a highly effective predator of the eggs and chicks of our rare endemic species – so we have to deal with it. On a positive note I encountered a family group of three birds on the path called “L’Allee Bodamye” I was walking from the central path junction in the island when I noticed a single SMR following me. I took the opportunity disturb the leaf litter with my feet in order expose the insects upon which the bird feeds and moved on. When I looked back there were three birds on the patch of scraped ground. Such a sight even today is significant as it represents approximately a 60th of the world’s entire population of this endangered species. So I turned to take a few photos. One of the adults on seeing that I had stopped however soon came forward making its “churring” aggressive call. So not wanting to stress the birds I cleared another patch of leaves and left them to their foraging.

L’Allee Sed. The path that leads from the west coastal path to the island’s main central junction (mentioned above) is called “L’Allee Sed” because it is formed by an avenue of casuarina trees. L’Allee Sed is one of the older features on the islands. Casuarina trees were likely planted on the island from the 1860s onwards to provide a better windbreak for the coconut plantations and I have found reference from 1907 to the stands on the island being a major feature. The L’Allee Sed is therefore recognised under the island’s management plan as an important historical and ecotourism feature of the island that needs to be maintained.

Sally lightfoot crabs. In my post of 5th July I wrote about this species of crab and its special adaptations to life in the breaking waves. I also mentioned that on occasion the cast off exoskeletons could sometimes be found. During my last trip I indeed find one on the southern rocks see photo in sidebar.

Bird Bulletin
  • I am pleased to report that both Paradise flycatcher fledglings are alive and well. Rachel Bristol, the Flycatcher Project Officer, is currently out on the island to follow up on the population so I should have more detailed news soon.
  • Sadly the ground-nesting Tropicbird to the south of the island that fledged its first chick in December appears to have abandoned its nest without breeding this time – there are few factors that may be involved and I will follow up on the site closely.
  • I noted only 1 Crested tern on the island last weekend interesting as I had recorded my highest ever count of 15 only a few weeks ago (see Post of 8th June).
  • Sooty terns are a common sight and sound overflying the island aside from the actual project area they are particularly notable displaying over the northwest coast at Pte Mme Guichard.
  • I checked on the White tern chick, the rescue of which I reported on in my second post of 5th July and am happy to report that it is growing well see photo in sidebar.

Wednesday, July 22, 2009

Studying the Seychelles warbler population on Denis…

As mentioned in my post of 8th June arrangements had been made for some researchers from Groningen University in the Netherlands to come to Denis to undertake a study of the Seychelles warbler (Acrocephalus sechellensis). The Seychelles warbler was introduced to Denis in 2004 as part of its ongoing national conservation plan (see post of 08/06 for more info).

The researchers Jildou and Peter arrived three weeks ago and were straight into their work. The establishment of a new population on an island offers plenty of scope for research. Jildou and Peter will be investigating the warbler’s population growth since 2007 and undertaking a detailed survey to ascertain survival and reproductive success in the population. Jildou and Peter are working under the supervision of Dr Jan Komdeur who worked in Seychelles for several years in the late 1980’s and early 1990’s. Jan was the man responsible for the propagation of the warbler to other islands that has done so much to enhance the conservation status of this endemic species. His detailed research of the warbler and its habitat requirements enabled the transfer of birds from the then sole colony on Cousin island to the islands of Aride and Cousine and latterly Denis.

Jildou and Peter are looking in particular at female mortality. There is evidence from the previous Denis survey in 2007 that the warbler population was skewed, with more males than females. Birds on a new island with abundant vacant habitat undergo more rapid reproduction than they do in established populations simply because resources are more abundant. Breeding is an energy intensive activity particularly for the females. It is postulated that this investment by the females may detract from their longevity and hence the development of a skewed sex ratio in the population.

Jildou and Peter will therefore be monitoring levels of stress in the birds by taking blood samples and checking for levels of oxidative stress, they will also be looking at the level of stress hormones in warbler faecal samples. They are furthermore looking at the levels of immunocompetence in the birds by assessing a variety of physical characteristics of the birds – as stress can affect immunocompetence.

This research is very interesting and has various ramifications for the planning of bird translocations in the future. From a Denis viewpoint, we are particularly interested in an update on the status of the population, its distribution and habitat use as this will help inform decision-making with regard to vegetation management on the island.

Keep checking back for more updates on Jildou and Peter’s endeavours.

Sooty tern update…

Part of the island’s management plan is in effect about turning back the clock. The southern portion of the island has been identified for restoration. The long term goal is to take this area back, as close as we can, to its original state when first discovered by man. De Trobriand the discoverer of Denis in 1773 left us a fascinating and quite detailed description of the island and its wildlife.

One of the dominant seabird species found on Denis at that time was the Sooty Tern (Onychoprion fuscata). Today one of the first aspects of restoration we are broaching is an attempt to re-establish a breeding population of Sooty terns on the island. Whilst we do not have specific records on the history and fate of the original sooty tern colony, we can draw certain conclusions from the island’s known development history and it seems probable that the bird has not successfully bred on the island for some 150 years.

We are now into the second year of this project and as such work has never been previously undertaken with the Sooty tern we are breaking new ground and learning as we go along. In this second year we have refined our approach following the results of last year and it has definitely been more successful (Previous posts cover the earlier stages of the project see: 19/05/09 and 02/07, 21/09 & 13/10 2008).

The sooty tern project was the focus of much my attention during my last visit to the island and it was most encouraging. On the Thursday afternoon I observed a few birds circling and a couple on the ground but it was on the mornings of Friday and Saturday that things were much more interesting. GIF volunteers Vicki and Georgia have been working steadily on the project and I hope that one or both of them will post soon on their perspective on the project. Both of them were present on Friday morning and the project area was alive with activity. Up to 37 birds were to be seen on the ground at a time with many more circling low over the area and calling. The birds on the ground were observed courting and mating and interacting as if a colony was under formation – it was fascinating stuff. The occasional bird was still seen to attempt to mate with one of the models as well. The next morning was much the same with up to 35 birds being observed on the ground at any time this time with the birds in general occurring in a single group.

It is unlikely that we will see any egg-laying on the island this year as, despite the delay in the onset of the southeast monsoon, egg-laying commenced in the existing Sooty colony on Aride Island in early June. Nevertheless the results this year are much improved from last and we continue to learn more about the bird’s preferences and how we might better design the project next year. According to studies the Sooty tern does not return to breed until it is 6 or 7 years old so it may well be that the birds we are attracting are young adults that are reconnoitring potential breeding locations for next year – let’s hope they keep Denis in mind!!!

Monday, July 20, 2009

Southeast monsoon.

Flying to Denis on Thursday 16th July it was clear that the southeast monsoon was blowing strongly and had finally, properly established. Seychelles has two seasons determined by the direction of the prevailing wind either the northwest trade winds or the southeast monsoon. The southeast monsoon has been very late establishing this year and this affects the habits of many animals notably the breeding activity of seabirds that rely on the seasonal winds and related currents to bring the small fish they need to breed and successfully raise a chick.

I hadn’t been to Denis for a couple of weeks and last time I was there the southeast was blowing intermittently. On Thursday the white caps of waves were visible throughout the flight from Mahe to Denis. As the plane descended and approached the island, choppy water was evident on the surrounding shoals and then I saw something that I have never previously seen. A plume of sand was being carried offshore from “Pte Mme Guichard” on the northwest point of the island, off the shoal and into deeper water.

I have been monitoring the cycles of sand movement on the northwest coast since December 2005 and there is definite evidence of erosion. The difficulty in assessing such changes however is the fact that there may well be ongoing long-term cycles of erosion and accretion for which we have no information. It is therefore not possible to see short term changes in coastal profile in the proper context. Such thoughts are further complicated by ongoing changes in global weather patterns and the related issue of sea level rise. It is important however to monitor trends in coastal erosion in particular on the shoreline where key infrastructure is located in order to inform management decisions.

On seeing this sand plume going offshore and into deeper water it occurred to me that such sand loss may be permanent. Normally when I fly into the island I have camera ready for in case of a good photo-opportunities but on this trip because of the cloudy weather and poor light I hadn’t bothered. So I had to scramble to get the camera and snap some shots… so not great but good enough to show the occurrence… see photos in sidebar.

There was further evidence of the onset and stabilisation of the wind on the island. The sand promontory at Pte Mme Guichard has been largely eroded – a usual part of the island’s beach profile dynamics. I had reported previously (see post of 8th May amongst others) about the recovery of vegetation a Belle Etoile on the east coast following the cessation of grazing cattle there. This had greatly changed the view of the area with the former open meadows and casuarina-framed vistas obscured by the dense growth and foliage of papaya thickets. Well the salt spray driven by the “southeast” wind has changed this dramatically the leaves are gone leaving the barren stems to point accusingly at the sky.

Another key issue related to the southeast monsoon is that it will also mean that the Sooty tern season should get properly underway… but that is the subject of another post…

Monday, July 13, 2009

Shells 2: The Minstrel Cowrie - Cypraea histrio

On Tuesday the 18th of November I posted on the mollusc Trochus virgatus and now, having not been to the island for a couple of weeks, seems to be an appropriate time to continue that theme.

During November we had some good high tides and wave action that served to wash up quite a few dead shells from the surrounding reef flats. At the same time I found the T. virgatus I also found a good specimen of the Minstrel cowrie (Cypraea histrio). The pictures below show the specimen of this beautiful species of sea snail and can be enlarged simply by clicking on them.

Jarrett (2000) states that C. histrio is very common in Seychelles where it occurs in shallow waters and rarely deeper than 3 metres.











Ref: Jarrett, A.G. (2000). Marine Shells of the Seychelles. Carole Green Publishing, UK.

Thursday, July 9, 2009

Day geckos (Phelsuma astriata and Phelsuma sundbergi)…

Visitors to Denis will all notice the bright green geckos that can be seen on the trunks of coconut trees and at night on the columns in the restaurant – where they lie in wait by a light to capture the insects it attracts.

There are in fact two species of day gecko to be found on the island the Lesser day gecko (Phelsuma astriata) and the Day gecko (Phelsuma sundbergi). Both species are endemic to the granitic Seychelles but are believed to have both been introduced (presumably inadvertently) to Denis. Gerlach (2007) states that P. sunbergi was first recorded on Denis in 1908 whilst P. astriata was introduced as recently as 1981. Of course lizards can and are known to colonise distant islands via floating vegetation so such matters are never entirely clear cut but the apparent recent nature of these colonisations does very much suggest a human vector. Regardless both of these species are now well established on the island and as species endemic to the central archipelago are more than welcome.

P. sundbergi is the much larger and heavier set species (getting up to about 20cm long including its tail) when mature and tend to be territorial. Typically one will be evident per coconut trunk or column on a boat shed or verandah and when two occur they will often be seen to fight. They are particularly noticeable to visitors as it is this species that populates the columns around the restaurant. They are typically bright green with on closer inspection, a light red freckling on the back of some individuals.

P. striata is significantly smaller (10 -12 cm including tail) and much less sturdy in build than P. sunbergi and can be seen on vegetation, tree branches, palm leaves and also on walls. It has visible pale belly and interesting red patterning on the bright green of its back and head. The adult has a distinctive red chevron on its head typically followed by two transverse bars on its neck (see photo in sidebar – this specimen has dots rather than the bars but it was a juvenile and the bars may form later). They typically have a spinal red line with patterns of red dots. On Denis these dots often merge to form a herringbone pattern (see sidebar). Occasionally a black P. striata can be seen this colour change is a reversible defensive stress response.

Wednesday, July 8, 2009

The Palm Spider (Nephila inaurata)

Arachnophobes need read this post no further – but of course do scroll down to other posts! - as this spider fits the bill as a pretty frightening beast if you are that way inclined.

The Palm spider (Nephila inaurata), also known as the “red-legged golden orb-web spider”, can get pretty big. I have seen them, including leg span, soup dish-sized and building their webs from the telephone lines to the ground in the south of the main island of Mahe!

They are fairly common throughout Seychelles and on Denis can typically be seen in their webs along forest paths. The spiders themselves are harmless – unless of course you are an insect – and during fieldwork I have often accidentally walked through a web and had a spider scrambling over me, generally doing the best it can to get off as quickly as possible.

Their webs are strong and are reputed to be able to ensnare even small birds though I have never observed such an occurrence. The large spider at the centre of the web is the female whereas the male is very much smaller and can often be seen nearby typically on the other side of the web (see photo in sidebar). I am often asked and do not have the answer for whether the female eats the males – I don’t think so – but it may be for good reason that the males are typically found on the other side of the web!

I have dithered as to whether to do a post on the palm spider for fear of putting off people from visiting the island. This however is the tropics and visitors to such destinations should expect to find life teaming in all forms. Seychelles in fact has very few creepy-crawlies when compared to tropical continental landmasses and none of them are dangerous. In the case of this spider it remains stationary in its webs in the forest and is not one that you need worry may come and visit you in your room. So don’t be put off, the Palm spider is in fact a very interesting species fulfilling its role and occupying its place in the island ecosystem.

Sunday, July 5, 2009

White tern (Gygis alba) rescue

The white tern (Gygis alba) is an unusual bird in several respects. In particular it does not build a nest but rather lays its egg in a hollow or fork of a branch. This requires some particular adaptations by the chick in particular the ability to anchor itself to the branch with its claws even before properly emerging from its shell. Chicks therefore have well-developed feet and claws whilst the rest of them is little more than a fluffy ball of feathers.

The strength of its claws was brought home to me a couple of weeks ago on the island whilst taking some tour operator representatives on a tour round the island. I was actually looking for a Seychelles warbler that I had just heard when I looked up to see a white tern chick hanging upside down from a branch. I initially thought the chick was dead but then I saw an adult sitting on the perch above and looked more closely at the chick. It was alive with breathing and eye movement evident and hanging by just a couple of claws of one foot… not a good situation.

The bird was a good 15 feet off the ground up a spindly ornamental tree near the main hotel complex. I went in search of a ladder and on my return, having with the assistance of some of the tour reps worked out how to properly extend it, still found the ladder too short for someone of my limited climbing capacity to reach the bird. Fortunately a young man from the garden staff was walking by and I asked him if he would be able to help. He took one rather dismissive look at the ladder, and proceeded to shin agilely up the tree retrieved the bird and replaced it on the perch where the adult had been!

I had been too preoccupied to get a photo of the chick whilst it hung precariously, but one of the tour reps, Amy Pearson, did get a shot of the rescue which she has kindly sent to me (see sidebar).

I went back the next week to check on the chick and found it well and on its perch - so a nice little feel-good story for all involved!

The “Sally Lightfoot” crab or Karkasay (Grapsus tenuicrustatus).

I have previously posted on the importance of hermit crabs in the island ecosystem (see post of 16th July 2008) and the work we have undertaken to look at the occurrence and populations of the three species that occur on the island.

Denis, of course, has other crabs of both land and coastal species and in this post I will focus on the “Sally Lightfoot”, known locally as “Karkasay” (Grapsus tenuicrustatus) which is a crab of rocky shores. It is interesting that the species occurs at all on Denis as the island is a sand cay without rock. Denis was formed during the last glaciation when sand piled up on a patch reef that today forms the reef flats around the north, east and south east coast of the island and can be considered, in some respects, as the “backbone” of the island.

The “rocks” that are to be found around Denis and that form the habitat for G. tenuicrustatus are in fact made of sand! A large part of Denis’ surface area is today actually made up of sandstone. Sandstone that was formed from the action of acids, leached from millennia of sea-bird droppings, acting to bind the coral sand particles together. There are in fact two layers of sandstone on the on the island suggesting that it may have been submersed at some point in its history before re-emerging above the waves.

This sandstone is not particularly strong – it being possible to break fragments of it by hand – it does nevertheless form a solid structure against wave action and can be found forming extensive wave-smoothed tablets along the east, south and south west coasts of the island and distinct outcrops at the southern point of Denis. This therefore is what provides the habitat for a rocky shore crab on an otherwise sand cay island.

G. tenuicrustatus is a herbivore that grazes on the algae that grows on rocks on the coast. Its sleek highly streamlined form, necessary for it to cling to rocks as waves break, gives it an almost alien appearance when seen in profile. Research elsewhere (Martinez 2001) has shown that a very minor shift in stance of the crab greatly reduces its drag in water and enables it to withstand 200% faster flow of water without being dislodged.

The Karkasay on Denis are alert and wary of intrusion, very swiftly retreating into crevices or if necessary jumping into the sea when someone approaches. Clearly this is a predator avoidance technique and though I have yet to sea anything predate them I imagine visiting herons and the ever present conger eels pose a threat - not to mention of course man, seeing as Karkasay make a good curry!

I was able to get some good shots of the crabs on the south and southwest coast (see sidebar). Of particular interest was that the crabs did not retract their eyes at the moment a wave hit, further evidence of their adaptation to the coastal environment.

Sometimes what appears to be a pink-red corpse of a crab can be found intact on the rocks – this is in fact an exoskeleton shed by a growing crab.

There are several other species of crab to be found on Denis and I aim to cover them in future posts…


Ref: Martinez, M.M. (2001). Running in the surf: hydrodynamics of the shore crab Grapsus tenuicrustatus. Journal of Experimental Biology, 204, 3097-3212, (2001).

Friday, July 3, 2009

Focus on the Seychelles Turtle Dove (Streptopelia picturata rostrata/picturata)

A lot has been written about the Seychelles turtle dove (S. p. rostrata) and its progressive demise by cross-breeding with the larger and introduced Madagascar turtle dove (S. p. picturata). Although there is no real consensus the general view is that Madagascar turtle dove was introduced probably as a released food supply by a calling vessel in the mid-19th century - though Beamish (1981) states that it was introduced as recently as the early 20th century.

The Madagascan race is larger than the endemic Seychelles race and males compete for access to mates. The males face off side to side and jump and bat their near wing on the ground in aggressive displays. Feathers puffed out, back arched and outer wing raised they attempt to intimidate their opponent by the impression of greater size. If this does not work, then fighting can ensue with the birds then hitting each other rather than the ground with their wings until supremacy is established. The advantage is clearly with the larger bird resulting in more successful breeding by the Madagascan males and the spread of their physical characteristics through the population.

Some authors go into great detail describing fine differences between the phenotype of the two races for the purposes of this post however; Penny’s (1974) description will suffice:

“ Rostrata has a vinous red head, a chestnut mantle, grey brown under tail feathers and is much smaller”

“Picturata has a grey head, purplish mantle, white under tail and is larger”

For many years it was reported that individuals exhibiting the rostrata phenotype were restricted to the small islands of Aride, Cousin and Cousine. Penny (1974) also cites Fregate which makes sense as though not small it is the most isolated of the granitic islands.

Whilst working on Cousine Island in the mid-nineties I undertook a survey of the turtle dove population on the island. I caught, if I recall correctly, some 120 birds and scored them on various characteristics from plumage colour on various parts of their bodies, eye colour and various biometrics including wing length. Each bird measured was ringed to avoid repetition. At the time my results suggested that 1 in 3 turtle doves on the island still exhibited strong rostrata characteristics. I still have all the data in an old logbook at home one of several topics that fit into the likely doomed “I must write it up someday category…”

In 1995 Chris Feare – yes the same Chris Feare who is now working with us on the Sooty tern project – published a brief paper on his findings of turtle doves on Bird Island. Where, though admittedly with a small sample, his capture and grading of the birds suggested a population very close to the rostrata phenotype. Feare goes on to suggest that a small number of birds were either introduced or colonised naturally in the latter half of the 19th century and had persisted there largely unnoticed until changes in vegetation in the latter part of the 20th century allowed the population to increase.

Although not mentioned in the literature (indeed Hill 2002 states that the birds on Denis are of the picturata form) I have found there is definitely considerable variation in the physical characteristics of the doves on Denis (see photos in sidebar) and though I have not gone to the lengths of capturing and scoring the birds physical traits (too many more important and pressing issues to address) I think the population on Denis may be of interest in that regard.

This is notable because if the population on Denis were scored for its phenotype and then managed over a period of years it may be possible to bring back the endemic rostrata phenotype throughout the population. This due to Denis’ relative isolation could be maintained with just periodic monitoring and management.

A project for the future perhaps…

Refs:
Beamish, T. (1981). Birds of Seychelles. Dept of Agriculture. GoS.
Feare, C, J. & E.L. Gill (1995). The turtle doves of Bird Island, Seychelles. Bull. B.O.C. 1995 115(4).
Hill, M.J. Ed (2002). Biodiversity surveys and conservation potential of inner Seychelles islands. Atoll Research Bulletin. July 2002.
Penny, M. (1974). The birds of Seychelles and the Outlying islands. Collins. ISBN 0 00 219829 0

Wednesday, July 1, 2009

Sooty Tern Update – encouraging progress!

Apologies for the delay in posting but paperwork deadlines have kept me very heavily occupied over the last 10 days – here’s hoping the effort pays off!

I paid a 24-hour visit to the island, weekend before last, in order to show some representatives of a potential donor agency the ongoing environmental work on Denis and also highlight some aspects that may be of interest to their organisation.

I made a special effort however to follow up on the sooty tern project during the visit and see how work is progressing and have some very encouraging news to recount.

I observed several birds circling very low over the project area and calling and also observed 3 birds landing. As we have seen before single birds that land, bow and display to the models but of course the models do not respond. However when they land in groups they can display to each other and this is our hope that sufficient birds can be attracted simultaneously down to the site such that they can cross-stimulate each other and begin the formation of a breeding colony.

That day though, I was particularly interested in the behaviour of one bird that appeared to be exhibiting “scrape-making” behaviour. This is the precursor to egg laying and of course a very exciting development for the project. The bird stayed on the ground for more than 40 minutes and was twice attended by another bird – perhaps its mate? See photos in side bar which, although somewhat overexposed (it was a very bright sunny day) and taken at the maximum zoom nevertheless, serve to show the birds on the ground in amongst the models. The bird was down on its chest and displayed the rocking side-to-side motion that accompanies the activity of making a scrape in the ground that it will later lay in. I was not though, due to the lie of the land, able to see whether the bird’s feet were in fact scraping at the ground in order to make a depression. Notably having a left a bird (presumably the same one) did later return to the exact same location. So fingers crossed!

That however is just the least of it! On the morning of Wednesday the 24th June I received a call from the volunteers advising me that 20 birds had been on the ground that morning and that they had observed 3 pairs mating. This is very encouraging and caused me to advise several interested parties including Prof. Feare in UK accordingly.

We are of course still learning as we go; such a project has never been attempted with Sooty terns before and we are continuing to refine the methodology as we progress. These developments however constitute a major advance and give us hope for the future even if this year we do not have birds attempting breed on the site.

Time will tell… check back regularly for updates.

Monday, June 15, 2009

Nature Notes 5.

Just back from the island, it was a brief 24 hour stay primarily to give a presentation and walk for some guests, so a quick summary of salient points noted below:

  • Sooty tern (Onychoprion fuscata) update. I stopped by the sooty tern project for an hour or so mid-afternoon on Saturday but only observed a couple of circling flyovers by birds. On Sunday morning however I met Vicki and Georgia at the observation platform and they had quite a lot to recount – most notably that they had observed a pair of terns landing that had courted and mated in the project area… this is most encouraging!!! In addition they had observed a bird attempt to court and mate with one of the plastic models – which goes to show that models clearly do provide the correct kind of stimuli!!! Whilst I was there on Sunday morning I observed a bird circle and land in the location … unfortunately I couldn’t stay and take photographs… but that will be a focus of mine during my next visit.
  • Observations on a Seychelles warbler (Acrocephalus sechellensis). Much along the lines of my post of June 8th , whilst pursuing one matter – in this case whilst sitting under the observation platform in the shade waiting hopefully for a Sooty tern to land – various other points of interest presented themselves. First my attention was drawn by the familiar clicking of a warbler’s bill as it took insects. The bird was very close by in a clump of low herbaceous vegetation consisting primarily of the spinach plant “Payater” (Amaranthus dubius). This was clearly a very fruitful area for it as it remained in this small clump for a good 20 minutes feeding busily on insects taken from the underside of the leaves. On a few occasions it took a prominent perch and looking above would launch itself straight up to aerially intercept a flying insect. It also paused in a more secluded site to preen. Judging from its behaviour, the somewhat mottled plumage on its breast and the less than rich brown colouring if its eye I got the impression that it was a subadult – probably recently departed from its natal territory and currently “floating” or in the process of establishing a territory for itself.
  • Ant-lions (Myrmeleon obscurus). Then looking down at the ground beneath the platform I became aware of several characteristic funnel traps of ant-lion larvae in the sand. These funnels with there very loose surface of sand are easily disturbed by passing insects such as ants. At the nexus of the funnel hidden just below the surface the ant-lion larvae lies in wait. When it senses the disturbance of sand in its “funnel” it shoots sand out from the centre knocking the unfortunate prey down into the centre where it is caught and consumed by the waiting predator. I watched fascinated by the occasional shots of sand that were sent out from the centre of each pit.
  • Carpenter bees (Xylocopa caffra). Finally whilst waiting under the platform I tried to get a photo of a female carpenter bee that was drawn by small flowers in the undergrowth. This has become something of a task for me… I have wanted to do a post on the carpenter bee for quite some time but I can’t seem to get a good photo of the female. I have several good photos of the male but the female with her black body and characteristic single large yellow band is another matter all together!!! The males move slowly from one flower to the next often pausing and hence allowing photos to be taken. The females however whilst much more readily noticed with their distinctive colouration and low rumbling buzz are very flighty seemingly never pausing long enough for me to get a decent photo… I shall endeavour to persevere…
  • Blue-cheeked bee-eaters (Merops persicus). Moving away from the Sooty tern project… regular readers will be aware of the presence of the beautiful blue-cheeked bee-eater on Denis for the last 6 months (See my post of May 23rd for the full account) and our interest in recording when exactly the last individuals leave the island. It had been thought that all the birds had left after the first week of this month – but during the tour I was giving on Sunday morning I observed two hawking from prominent perches on the island’s southern beach and then later repeatedly heard one near the hotel complex… so a few stragglers yet remain. We will continue to monitor.
  • Flycatcher news (Terpsiphone corvina). Great news from Mervyn working on the Flycatcher project! A second bird has now fledged successfully giving us much hope for the future.

Wednesday, June 10, 2009

Outreach Programme – Launch of Denis Island Newsletter.

I have posted in the past about various aspects of our outreach programme under the islands 2008-2012 Environmental Management Plan. The raising of public awareness both at home and overseas is an important component of the overall sustainability of the island’s environmental initiatives – and this blog forms part of that outreach.

In recent months we have had some excellent national media coverage on the TV, radio and in the press. We also, thanks to the assistance of the Seychelles Broadcasting Corporation, have had some great international coverage on CNN. This has all been very encouraging and has resulted in positive feedback.

We are also active on the island as well; GIF personnel provide walks and talks for hotel guests and the island has also constructed an information centre which now just awaits the arrival of posters and pamphlets on the island’s environment in English and French for it to open.

Now last week we launched an Environmental Update Newsletter for circulation on the island in Guests’ rooms and in the hotel complex. The intention is that there will be an issue every 2 months that will give clients the opportunity, at their leisure, to learn about the islands wildlife and environmental projects.
Simply click on the images below to enlarge and read the first Newsletter.

Tuesday, June 9, 2009

Sooty tern project – update and Post by Prof. Chris Feare

I have been to the island 3 times in as many weeks largely due to the need to follow up on preparations for and implementation of the island’s sooty tern project (see my post of 19th May for background information). Professor Chris Feare, the world expert on the species, is in the Seychelles at the moment having come out to oversee the project set-up on Denis. Our two volunteers, Georgia French and Vicki Willits, have also arrived and work is now ongoing.

Following on from our findings last year the models and loud speakers have been set out in the project area. One loud speaker has also been mounted half-way up the trunk of a coconut tree facing out to sea along the prepared entry flight path in order to attract birds that may be flying along the coastline. The southeast monsoon has been late to establish this year and this has a bearing upon the behaviour of Sooty terns – with fewer birds over-flying the island than we would normally expect. The wind has however now set in and we hope that bird numbers will pick up in the next week or two. Despite this, landings have been relatively good with in fact more landings reported in the first week of work this year than throughout the entire season last year! This is very encouraging and underlines I feel, that the lessons learnt regarding the birds’ preferences last year are now reaping benefits in our work. Of particular note was the landing of a pair of birds which then commenced a courting display – exactly what we are hoping for!!!

Chris Feare has kindly written a post (see below) for this blog that sets our work in the broader context of his long term study of Sooty terns in the Seychelles archipelago:

"While Sooty Terns do not command the iconic status bestowed upon some of Seychelles’ rare endemic birds, such as the Seychelles Magpie Robin, Seychelles Warbler and Seychelles Paradise Flycatcher, the Sooty Tern is in fact the Seychelles’ most numerous bird. It breeds in huge spectacular colonies on Bird and Aride Islands, and on the more remote islands of Desnoeufs in the Amirantes, Goelette Island of Farquhar Atoll and Wizard Island of Cosmoledo Atoll. Despite remaining so numerous, Sooty Terns have faced a number of threats since man settled the islands in the mid-eighteenth century. These include the collecting of enormous numbers of their eggs, alteration of the habitats of their nesting islands and the introduction of mammalian predators such as rats and cats. As a result, several former breeding colonies now lie deserted, particularly those on smaller islands close to the main centres of human occupation.
Concern for the species led to their receiving various forms of protection but these are extremely difficult to enforce on remote and often uninhabited islands, and some of the earlier conservation attempts were based on insufficient knowledge of the birds’ biology and behaviour. My own studies of Sooty Terns in Seychelles, now spanning 37 years, along with investigations of colonies elsewhere in tropical oceans, have provided information on their needs and lifestyle that can contribute greatly to their conservation. For example, we know from recent events on Bird Island that restoration of prime habitat, by removing old coconut plantations and encouraging the development of indigenous herb vegetation such as purslane, can lead to a dramatic recovery in numbers. Controlled harvesting of their eggs can also play a part by placing a value on the birds while at the same time regulating the number of eggs that can be taken and the islands upon which harvest is permitted. And eradication of alien predators benefits all indigenous animals, not just Sooty Terns.
Sooty Terns are long-lived birds: on Bird Island ringing studies have revealed several birds 34 years old. In the absence of disturbance, adults usually return to nest on the same island year after year. In an attempt to re-establish a colony on an island known to have supported a large colony 200 years ago, an experiment is currently taking place on Denis Island (see recent blogs). Here, a small area of forest has been cleared and plastic models and broadcasts of Sooty Tern calls are being used, with some success, to attract birds to the island. Once settled, we hope they will continue to return and breed.
Despite our increased knowledge, however, Sooty Terns still hold many mysteries. In particular, we do not know where they feed while they are breeding. Nor do we know where they go when the leave Seychelles after breeding. Ring recoveries in southern India and in northern Australia suggest that they travel far. But we shall not get a better picture of their movements until tiny satellite transmitters, suitable for attachment to Sooty Terns, are available. Only then will we be able to determine whether another of man’s activities, intensive fishing of tuna, presents a threat to these magnificent birds. Sooty Terns do not eat tuna, but they are totally reliant on these predatory fish to drive smaller fish, like sardines, to the ocean surface where they become available to the birds. So if the Sooties prove to feed where tuna are being over-fished, the birds’ populations will be threatened no matter what conservation measures are in place on their nesting islands."

Monday, June 8, 2009

100 posts – one thing leads to another

This post marks a landmark for the Denis Island Environmental Update blog – it being the hundredth post since I started the blog in July 2008. The blog was established primarily to provide information to hotel clients many of whom return periodically to the island and expressed an interest in being able to follow up on our projects on the island during the time in between their visits.

It did occur to me when starting out that whilst I would initially have plenty to write about it would be difficult after a while to find new and different matters to cover. In fact the opposite has been the case, every visit to the island seems to provide numerous new topics to report on and it is not lack of subject matter but rather lack of time to write them that effectively limits the number of articles I am able to post. Frequently I leave the island with a list of 6 or 7 new topics for potential posts but many fall by the wayside as they are replaced by new options from a subsequent visit before I get the time to actually write them up.

A perfect example of subject overload happened during my visit a week ago. I noted on arrival a sudden and widespread commencement of nest building by the island’s Brown noddy colony (see post of 31st May). I spent some time photographing the birds nest-building in the coconut trees at the entrance to the main hotel complex. Following this I decided to go and try and photo the birds gathering nest material on the beach crest. As I approached the beach however I noted a white tern alighting on a branch next to its chick with a beak full of fish so I was then distracted by this and occupied by attempts to get a photograph that captured the moment of food transfer from adult to chick. I failed to do this but decided to wait for the return of the adult and try again. After a few minutes a white tern did indeed fly into view bearing fish but this was a different adult flying to another chick higher up in the same tree. Whilst trying to feed the chick a small fish was dropped and fell to the ground. This nutritious morsel was immediately picked up by a moorhen which in turn ran off in the direction of a scaevola bush. I suspected that it also had young to feed and I now set off to try and capture that image. The moorhen did indeed have two chicks hiding in the bush and it thereafter sectioned up the fish to feed to its young – paying me no attention whilst I remained still nearby. I stood partly behind the scaevola bush so as not to make the birds feel threatened whilst I photographed the feeding. It was whilst standing there that I noticed that the flowers of the bush were alive with large numbers of a fly with very distinctive red-eyes – so having never previously observed such an aggregation I photographed these insects so as to enable their identification at a later date.

After this I returned to my original plan of going to the beach crest to photo noddies collecting nesting material. I positioned myself on a beach chair and waited for the right opportunity. I was soon photographing several noddies busy gathering casuarina fronds on the beach when I noticed a ghost crab approaching me along the beach. These animals are normally very wary and difficult to photo but as I was stationary on the seat the crab appeared not to notice me and continued to approach so I took the opportunity to photo it also. As it passed along side me I turned in the chair to try and get a better shot but this movement alerted it to my presence and it immediately sought refuge down the nearest crab burrow. I kept my camera trained on the burrow entrance however as I was confident that this burrow belonged to another crab which meant the new arrival would rapidly be forced out by the resident. Sure enough the crab soon appeared at the entrance but seeing me shot back down. This happened a couple more times and I waited, confident that the crab would soon have to emerge and I would have another opportunity to photo it up close. What happened next however really did surprise me and was the first time I had ever observed such behaviour. The crab did indeed re-emerge but this time clasping the resident crab, which was a bit smaller, in its pincers. It then proceeded to castaway the smaller crab and return back into the burrow which it had obviously found so much to its liking that forcible eviction of the owner was the next logical step!!!

I then just walked 30 metres down the beach and encountered 15 Greater crested terns – the highest count I have ever recorded on Denis – better yet they very kindly contrived to position themselves such that I could fit them all in the frame of a single photo thereby providing proof of the new record!

So through the simple idea of taking a photo to complement a post on Brown noddy nest-building one thing had led to another over a period of 30 minutes or so to encounter five other potential articles… so what to write about next?

Focus on warblers…

The Seychelles warbler (Acrocephalus sechellensis) is an iconic species for Seychelles conservation. In the 1960s the entire global population of only 20-25 birds was restricted to a small area of mangroves on the tiny island of Cousin. This led to the purchase of Cousin by the Royal Society for Nature Conservation in 1968 and the subsequent management by the then International Council for Bird Preservation (now BirdLife International).
The purchase of Cousin in order to save the warbler is often considered the dawn of modern conservation in Seychelles. In the following years natural vegetation was allowed to regenerate on Cousin and the Seychelles warbler population expanded and spread throughout the island. In 1988 warblers were introduced from Cousin Island to Aride and then to the neighbouring island of Cousine in 1990. Both introductions proved to be successful in particular the introduction to Aride where birds were reported to be nest-building within a day of their release on the island! The population of warblers on Aride today numbers more than 2,000 birds and the world population now likely over 3,000 – a most remarkable success!
58 Warblers were introduced to Denis Island in 2004 and follow up surveys of the island population 2005, 2006 and 2007 have shown a steady expansion of the warbler population on the island. The introduction of the warbler to Denis contributed to the downgrading of the threatened status of the species to Vulnerable under World Conservation Union (IUCN) criteria.
Logistical problems meant the island was unable to host researchers in 2008 to follow up on the monitoring of the population but I am happy to report that a survey of the population will be undertaken in 2009 so keep a look out in the coming months for updates on the status of the Seychelles warbler on Denis Island.

Sunday, May 31, 2009

Breeding seabirds

Just back from the island again and more developments to record.

The Brown Noddy (Anous stolidus). In my last post (Nature Notes 4 of 26th May) I recorded that there were currently a lot of white tern chicks in evidence around the island. The first thing I noticed on arriving on Denis on Thursday was the rapid and widespread onset of nest building amongst the island’s Brown noddies. The pathway leading up to the main hotel building was alive with the squawking refrain of the birds from the crowns of all coconut trees. The Brown noddy builds a simple though often rather large and untidy platform of twigs, casuarina fronds and sea weed at the base of the palm leaves where the large stem forms a natural gully where it joins with the trunk of the tree. The coconut trees in the hotel garden are particularly busy with many of the trees harbouring 3 or 4 nests. This density is not reflected elsewhere with trees typically having only 1 or 2 nests per crown. I am not sure why this should be, but I am inclined to think it is linked to the spacing of the trees and the lack of other canopy which provides easily navigable flight paths for the birds to access all the suitable nesting niches a tree has to offer. This coupled with the relative shortness of the trees in this open environment means they are sheltered from much of the wind by the hotel, readily accessible and yet secure – making them ideal for nesting.
I spent a while trying to get some photos of this nest-building activity – one bird would remain on the nest platform whilst the other would fly back and forth gathering and bringing material which it would then give the other which would incorporate it into the nest structure. The noddies were particularly busy collecting nesting material on the beach crest around the hotel where the last high-tide had washed up a lot of suitable material. The arrival of the bird bringing material would initiate another burst of harsh calling between the pair including bouts of their distinctive, bond-forming nodding behaviour which gives the birds their name.

White-tailed Tropicbird (Phaethon Lepturus). I also reported in my last post the return of the tropicbirds to the nest site that successfully produced our first confirmed fledging from a ground nest for this species. I checked on the nest again on Saturday and the bird was still present presumably incubating. The nest site is immediately adjacent to the path and I hence decided to cut a palm leaf and lean it against the Casuarina trunk thereby screening the nest from passersby on the path and thus hopefully reducing somewhat the stress on the birds – I will provide feedback periodically. We also now have a fourth confirmed ground nest on the island. This nest north of the runway and behind the staff quarters at “L’Allee Coco Rouge” is cosily placed amongst some old logs and currently contains a well-developed chick (see photo in sidebar).

I have been following the development of Denis as a seabird colony in detail on this blog. It is of significant interest to record the recovery of seabird populations following the cat and rat eradications in 2000 and 2002 respectively and Denis is making good progress.
The island currently supports breeding populations of: Brown Noddy, White terns (Gygis alba), White-tailed Tropicbirds and Wedge-tailed shearwaters (Puffinus pacificus). The island also supports a large roosting population of Lesser Noddies (Anous tenuirostris) which we hope may in time develop into a breeding population and of course the island is actively undertaking a project to re-establish a Sooty Tern (Onychoprion fuscata) colony.

Tuesday, May 26, 2009

Nature Notes 4

Notes from my last visit to the island and quite a few items of interest to report:

  • Magpie-robin news – firstly and sadly I have to report that we appear to have lost the poorly female that I reported on in my post of May 19th. There being no flight on Wednesday of last week the antibiotics, syringes etc… could only be taken to the island that Thursday and Catherina has not sighted the bird since Wednesday and we must now fear the worst. We do now however have a fresh stock of antibiotics with a long shelf-life on the island being kept in the fridge in case it should be needed in the future.
  • Flycatcher news – on a positive note our first flycatcher fledgling (see post of 21st April) appears to be prospering and there are currently 3 other breeding attempts ongoing in other territories.
  • White terns (Gygis alba) – we have been having a prolonged period of very hot weather in the central archipelago. There is typically a period of 3 or 4 weeks in April/May when the wind drops and the weather is very hot and dry before the next season establishes – but this year it has been going on for a couple of months. A change in the wind can effect water temperature and prevailing currents which in turn impacts upon the availability of the small fish that sea birds depend on to feed their young. The impression on the Denis at the moment however is that food is in abundance as we are experiencing a marked surge in the number of young white terns on the island. Let’s hope that food availability remains sufficient to see them through to independence.
  • White-tailed tropicbirds – I am delighted to be able to report that the site that produced our first confirmed tropicbird fledgling from a ground nest since the eradication of rats in 2002 is once again occupied by the female. Those regular readers of the blog will recall how I followed the development of “Tina” last year in detail on this blog and was delighted to report her successful fledging in the week of Christmas. Well her mother is now back on the nest site and possibly already incubating another egg. Another great benchmark in the recovery of the island’s ecosystem!
  • Greater Crested terns – birds are still to be seen each morning at Pte Mme Guichard and then in the afternoon on the sandstone outcrops just off the southern coast. There are currently nine birds in residence.

Saturday, May 23, 2009

Observations on the Blue-cheeked bee-eater (Merops persicus)…

Now into the fourth week of May and the Blue-cheeked bee-eater is still a common sight on Denis. My impression is that numbers have increased again over the last month with perhaps 30 or more on the island. Following the major influx in November when some 500 or so birds descended on the island. I recall watching literally hundreds hawking over the runway in the evening at the end of that month. The island was alive with these bright green birds with, so it seemed, practically every prominent perch along the paths occupied by yet another bird and their “trilling” call to be heard everywhere.

Numbers rapidly dropped after a few days but a few have been present ever since. During April the numbers went up again presumably as birds were passing through Seychelles this time on their route back north to their summer breeding grounds in southern Asia. Coming to the island on May 21st I frankly didn’t expect to see any as I presumed they would have all flown North by now – but the first bird call I heard as I got of the plane was that of a bee-eater and I could see 4 of them hawking over the beach by the runway. Later that day I saw several more along the east coast at Belle Etoile and more again around the hotel complex and late that afternoon I observed ten to a dozen feeding over the runway.

The next morning I went to photograph the beach outside the main hotel complex as part of a long term study of beach movement and erosion that I have been doing since 2005 when I encountered another bee-eater hawking from a perch on a fallen tree branch that had been washed up. I have learnt over the last 6 months that the bee-eaters are very alert and rather cautious and generally won’t let you get at all close before moving on. This bird however was otherwise occupied as the inshore breeze early that morning appeared to be channeling insects along the coast right past its vantage point. It was therefore very busy securing its breakfast and seemed little concerned with me.

Every 30 seconds or so it would dart of its perch in pursuit of an insect catch it and then stunt and turn in amazingly tight arcs to return to its original position to await its next passing snack. Over the next half-hour I utilised each of its forays to edge incrementally closer to its perch then as I got within about 10 -12 metres the sun came out from behind the clouds and giving good light to photograph the bird and capture the stunning colours of its plumage (see side bar). I was absorbed by this process; with every flight I got a few inches closer and so I believed each set of photos would be that little better than the one before.

I was then fortunate enough to observe some very interesting behavior. The bee-eater returned to its perch with a very large prey in its beak aptly enough it was a large bee – a male carpenter bee in fact.The bird then proceeded to beat the bee against the branch giving off a surprisingly loud “Thok, Thok, Thok” drumming noise as the insect’s exoskeleton hit the wood. Finishing off this bee was not to be an easy task however, despite this vicious beating! One such hit served to dislodge the bee from the bird’s beak and it was off… in a low careering flight over the sand away from its would-be captor. The bird was immediately in pursuit and in the space of 20 feet had re-captured its prey and then promptly returned to its perch to continue the drumming! This scene played out four times. Four times the bee escaped and flew for its life, four times the bee-eater shot after it recaptured it and returned to its post to continue the assault. It was fascinating to watch the blend of beauty, savagery and efficiency embodied by this stunning bird. The blows were administered by a severe whipping action of its head and neck a photo in the sidebar shows how the bird has actually turned its head 180o in order to imbue the whip-lash action with optimal force! Eventually the bee was subdued and then promptly consumed – the whole process from first capture to swallowing had taken a good 4-5 minutes.

The bird then continued with its business and I with mine edging progressively closer in search of that “perfect” photo and then suddenly it was gone. I waited for another 5 – 10 minutes in the hope it may return but it had flown off south-west down the coast doubtless to find another strategic point to continue its hunting.

I was very pleased with my morning’s “work” and I think – and I hope you agree - I was able to catch some good images of this truly wonderful bird.

Tuesday, May 19, 2009

Sooty tern (Onychoprion fuscata) project – year 2

It’s getting round to that time of year again! I have just received a shipment of new models (see photo in sidebar) so we can increase the density of models in the trial area this year. These models are closer to the actual size of the Sooty tern and are in fact magpie models that have been re-painted to appear like Sooty terns. When Denis was first discovered in 1773 it hosted very large seabird colonies including a large population of Sooty tern. Human impact on the island over the next hundreds years was very extensive and it is likely that the ground nesting sea bird colonies were extirpated within that period.

The environmental management plan for Denis has set aside the southern portion of the island for restoration to as close as possible to how it was when first discovered. The attempt to re-establish a colony of Sooty terns on the island forms part of this initiative.
The project commenced last year (see my posts of 2nd July, 21st September and 13th October 2008 for more information) with the preparation of the habitat area and the trial of different habitat and stimuli combinations including 2D and 3D models and the broadcasting of colony noise from loud speakers.

The first year of work and its structured approach allowed us to learn a good deal about the preferences of the birds and the trial area will be set out this year to reflect those findings and we are optimistic about the potential for 2009.

We are working with Dr Chris Feare who is a leading ornithologist and has been working on Sooty terns in Seychelles for many years. Chris will be arriving at the end of this month along with a couple of volunteers who will assist with the monitoring of the scheme this year - as well as undertaking other work.

I will report regularly on the project and its progression – success is by no means guaranteed but we are again breaking new ground here on Denis Island and should we achieve our objective it would represent another world first for the island - so do keep checking back for news on the Sooty tern project over the coming weeks…

A poorly Magpie-robin…

I received earlier today a call from Catherina on the island telling me that she had sent an e-mail with photos of an adult female SMR that was showing signs of ill-health. The posture, plumage and behaviour of the bird were not good and furthermore its droppings were liquid.

E-mail communications followed with Rachel Bristol and I then spoke with Dr Melanie to the vets department on Mahe. It was decided to get a broad-spectrum antibiotic that could be administered by injection to the bird. So I then went to the vets department purchased a bottle of Oxytetracycline and the smallest syringes and needles available.

The treatment entails capturing the bird and injecting 0.1ml into the bird’s muscle tissue and repeat in 3 days or so. This method has been used successfully previously on SMRs. So it is to be hoped that this problem is based upon a bacterial infection and that the treatment reaps benefits.

Unfortunately by the time I got the call from Catherina it was already too late to catch the plane and there being no flight on Wednesday we will not be able to get the medicine to the island before Thursday – hopefully it won’t be too late.

The tetracycline has a long shelf life so we can keep it in the fridge on Denis for about a year and use it on other birds should the need arise.

Check back regularly for news on our poorly magpie-robin.

Thursday, May 14, 2009

The Seychelles Flycatcher (Terpsiphone corvina): whiskers, “hair-dos” and mimicry…

In my post of 9th April I wrote about the whiskers clearly evident on the faces of both male and female flycatchers (Terpsiphone corvina) and postulated on what their purpose might be. Whilst drafting that post I spoke to Rachel Bristol, Project Officer on the Flycatcher project. We talked about the whiskers and Rachel also commented on head plumage of the birds referring to it in her inimitable style as a “spiky hair-do”. Rachel subsequently sent me a wonderful photo of a male flycatcher in hand which clearly illustrates both features (see sidebar).

Then after her last visit to Denis, Rachel called to update me on her findings and mentioned something new of real interest namely that the Seychelles magpie robins (Copsychus sechellarum) in some territories had begun to imitate the song of the Flycatcher.

I have in the past written about the ability of Mynah birds to mimic the calls of the Seychelles magpie robin on Denis. The Mynah is a renowned mimic and I would not have been at all surprised if they had already begun copying the Flycatcher’s call and causing confusion in Rachel’s attempt to monitor the flycatchers on Denis. The Seychelles magpie robin is another matter and this is of particular interest because until the introduction of Flycatchers to Denis in November the two species had not co-existed on an island for a hundred years or more. This co-existence is therefore a new experience for the all the birds and also a time of great interest for ornithologists to see how the two species will interact. The feeding niche of the two species is largely distinct and their territories overlay each other on Denis without any evidence of negative interaction but the Magpie robins adopting the song of the flycatcher may conceivably lead to some confrontations in territories – at least in the short term

I was involved with the transfer of Magpie robins to Cousine Island in 1995. The overall population was much lower back then and the habitat on Cousine despite my efforts over the preceding year or two was still limited for the species. As such a very precautionary approach to the introduction was undertaken - two young surplus males from Fregate were introduced to the island and latterly an old male which had been displaced from its territory on Fregate and following injury had been nursed back to health by hand. These birds were surplus and somewhat expendable and the intention was to see how they fared on Cousine before any precious females would be risked. (The birds did settle and the old one ended up fathering more offspring when females were latterly introduced). Initially however what was remarkable was the very limited song variety of the young males. One of them just continually repeating the same three note refrain until it would put one’s teeth on edge! When the old male was introduced however he had an extensive variety of tunes suggesting that birds acquire/learn new songs over time and are not born with a pre-programmed repertoire. This thought was re-enforced when the younger males began to expand their own tune list once the old male had been introduced.

Now here on Denis nearly 15 years later we have further evidence of the capacity of the Magpie robin to learn new tunes and styles.

Wednesday, May 13, 2009

Observations on the Seychelles blue pigeon (Alectroenas pulcherrima)

In my post of 10th August 2008 I wrote at length about the colonisation of Denis by Blue pigeons over the last 10-15 years and how today the island hosts a quite large and healthy population. There are no earlier records of blue pigeons on the island from visits in the early and mid-20th century or the 1970s so it would appear that man-induced changes have created suitable habitat on the island to enable it to establish a population on Denis.

In particular human activity has introduced various broadleaved tree species such that today some 30% of the island has a broadleaf canopy – and ongoing vegetation management programmes means this is likely expand considerably in the coming years.
Of particular note however are the fig (Ficus nautarum) and banyan trees (Ficus benghalensis) which now prosper on the island. The blue pigeon particularly likes to feast on the fruit of these trees. The small bright red fruit draws the birds in flocks to even very young trees – with at least 23 birds being counted in just one fig tree in 2008.

I have also frequently observed birds feeding on the white berries of the coastal bush “Veloutye” (Scaevola sericea) in the hotel grounds and around the southern point. During my visit last month I was able to capture a good photo of this behaviour (see sidebar). During the heat of the day it also common to see them in small groups perched in Bwa Kassan (Guettarda speciosa). The impression I receive of this behaviour is that the heavy shade offered by this coastal tree is ideal for the birds to shelter when the sun is high in the sky without them having to stray too far from a berried Veloutye bush.

Evidence of regular breeding continues with juveniles frequently being seen around the island – including one instance of twins I encountered a few months ago. The Blue pigeon is a remarkably beautiful bird with its red wattle and eye, powder grey neck and slate blue wings and lower body. The juvenile is very different however with no red colouration and drab grey and slate plumage with a tinge of an almost moldy green to the wings. One juvenile very kindly perched conveniently for me to photo in April (see sidebar).

Friday, May 8, 2009

Nature Notes 3

A belated summary of various observations following my visit to the island 16-18th April:

Blue-cheeked bee eaters (Merops persicus): I was very interested to find bee-eaters still present on the island we have had some birds stay on the island since the mass “invasion” in November when some 500 turned up for a period of days. Numbers rapidly declined after that, but there have always been some on the island since then. Interestingly during this last visit numbers definitely appeared up compared to March with several birds at a time to be seen hawking over the runway and from bushes along the east coast. A few days later I received an e-mail from Adrian Skerrett of the Seychelles Bird Records Committee (SBRC) asking whether Denis had received a new influx of bee-eaters as other islands had reported new sightings. It appears that birds heading north again to summer breeding grounds have passed back through the Seychelles archipelago. The mass influx of November and this return has apparently been seen throughout the archipelago and Adrian is working on a paper that summarises this migration pattern over the last 6 months. It is difficult on an island the size of Denis to estimate the number of bee-eaters that are present at any one time but I would have guessed there were approximately 20-25 on the island during mid-April representing an increase of 10-15 from March.

Whimbrels (Numenius phaeopus): A very distinct decline in Whimbrel numbers was evident. In November I counted a single flock of some 115 birds just on the reef flats off the North east coast and they have been abundant throughout the northern winter. A few birds stay all year on the island – presumably sub-adults – but it is clear that the bulk have started to return north again with only a few to be seen in small groups around the island in April.

Greater crested terns (Thalasseus bergii): a common sight in the morning at Pte Mme Guichard and later in the day on the sandstone outcrops just of the islands southern point – there currently appear to be nine birds on the island.

Grey Heron (Ardea cinera): The grey heron I first recorded in February is still resident spending quite a bit of its time now on the northern beach of the island hidden in amongst the fallen trees that project out across the beach and into the sea there.

Green turtle (Chelonia mydas). During my usual rounds I encountered my first green turtle track of the year – Green turtles can nest all year round but they show a distinct peak in nesting activity in the May-July period.

The island’s cattle have been kept north in the farm area at the estate for several months – being fed primarily on coconut shoots. This has allowed the vegetation at Belle Etoile to recover significantly in particular the Indian Mulberry trees (Morinda citrifolia), which the cattle particularly like to browse, have re-sprouted dramatically giving the pasture a more of a shrubland look. I also noted a lot of cotton plants in seed. Cotton (Gossypium hirsutum) was grown on Denis in the 1830s – 1850s and was a major cash crop for Seychelles at the time. Despite it being over 150 years since its cultivation it can still be seen in scrubland areas on the island. It has also been quite a weed in our sooty tern project area where removal of the coconut trees last year created the space and disturbed ground it needs to prosper.

Monday, May 4, 2009

The Green Islands Foundation (GIF) is committed to the mainstreaming of sustainable development. In the context of Seychelles, our chosen focus is on the key economic activities of Tourism, Fisheries and production landscapes. GIF has a sustainable development programme ongoing on the island of Denis (see http://denisisland.blogspot.com/ for more information) and is also keen to promote and facilitate similar initiatives on other islands. GIF has been working with three islands on the development of a common approach to maintaining their island’s rodent free and has just had an article published in the national press highlighting the importance of these islands and their rat-free status to national environmental initiatives.

Simply click on the image below to enlarge and read the article from today’s (25th May) Nation Newspaper.




Monday, April 27, 2009

Observations on Great and Lesser Frigatebirds (Fregata minor and F. ariel).

The Frigate bird is an iconic species in Seychelles - soaring on the breeze a large dark bird with its characteristic arched wing profile silhouetted against the bright blue sky - it has been adopted as a symbol by 3 islands in the central archipelago. Both species can be seen quite regularly in the central archipelago, though neither breed here, their nearest large breeding colonies being situated on Aldabra.

Aride island hosts the largest roost in the central archipelago with a seasonal peak of some 4,500 birds. Skerrett et al (2001)[1] states that small roosting populations also occur on Cousin and Bird Island. I lived on Cousin (1990-91) and clearly recall Frigatebirds roosting in a single casuarina tree, ignoring all others, north of “Anse Fregate”. That tree latterly fell however and I do not know whether the small roosting population on Cousin persists today. What I do know however is that Denis harbours a regular if small roost of some 40- 50 birds. Both species are represented though as is normal throughout the central archipelago the great out number the lesser.

On the Saturday morning of my last visit to the island I observed 6 frigatebirds stunting and swooping at not too high an altitude over the runway so I took some photos in the hope that the results would be good enough to differentiate between the species for the blog.

The photos are not the best – standing looking almost directly upwards, trying to zoom on and photograph rapidly moving birds not being one of my strong points! – but they are sufficient however to discern identifying characteristics.

The lesser frigatebird adult has the abbreviated white chest and inner wing patch, whilst the adult male great frigatebird is entirely black save for its red throat patch (barely visible in the sidebar photo).

Interestingly I was also able to photo two immature great frigate birds one white-headed and one buff-headed. Skerrett et al (2001) state that the white-headed birds are from the Aldabra colony whilst the buff-headed sub-adults originate form breeding colonies even farther afield! Click on the images below to enlarge.


[1] Skerrett et al (2001). Birds of Seychelles. Helm Field Guides, London.

Thursday, April 23, 2009

A familiar and punctual friend – the Danaid Eggfly (Hypolimnas misippus).

During my island visit last weekend I encountered a familiar friend the diadem butterfly or Danaid eggfly. During the mid-90s I worked on Cousine Island and recall seeing this beautiful butterfly, the male of which has a very distinctive wing decoration of 3 large clear white spots on a sooty brown background (see photos in sidebar), in successive Aprils. When I subsequently moved to Mahe I was struck by the fact that I again saw the butterfly over several years on successive Aprils.

This seasonal punctuality has continued on Denis I had regular sightings of the species last April flitting rapidly along the woodland fringe at Belle Etoile and then I had the opportunity to photograph a female in the hotel gardens (see sidebar). This last visit to Denis I encountered two separate males exhibiting territorial and display behaviour and was also able to get some good shots of one of them hence enabling this post. The species is dimorphic with the female being a mimic of the plain tiger butterfly (Danaus chrysippus) but also showing variations in form.

Gerlach and Matyot [1] state that the species is seasonal with adults flying from December to April - but they also note that they are most commonly observed in March-April.

H. missipus is a common butterfly with a pan-tropical distribution and polyphagous eating habit. It is known to feed on species of Asystasia, Portulacaceae and Ipomea all of which are common and abundant on Denis and so it seems likely that this beautiful butterfly will grace Denis for many Aprils to come.

[1] Gerlach, J. & Matyot, P. (2006): Lepidoptera of the Seychelles islands. Backhuys Publishers, Leiden, The Netherlands.