Eradication of Common Mynas from Denis Island, Seychelles, 2010 (Courtesy Prof. Chris Feare)

An attempt to eradicate Common Mynas Acridotheres tristis from Denis Island, Seychelles, began in late May 2010. The justification for the present control is evidence that mynas are directly and indirectly impacting negatively on the populations of some of the introduced endemic birds. An earlier attempt had been made, mainly using Starlicide (a toxicant that demonstrates some specificity to certain bird families, including mynas) in the early 2000s but this attempt was abandoned after a contemporaneous rat eradication attempt had failed; a subsequent rat eradication was successful. Now that four species of Seychelles endemic bird have been introduced to Denis, this toxicant is considered too dangerous for the endemics to be used as a primary control measure and the current attempt to remove mynas is centred on trapping.
In the initial stages two kinds of trap were built and tested: funnel traps, which rely on attractive food to entice mynas into the traps, and decoy traps, which use a live decoy myna in a central compartment to attract nearby mynas. Mist nets were also used in initial trials where flocks of mynas concentrated, as were fine nylon nooses placed on the ground among bait. In trials, only decoy trapping proved effective and the eradication attempt now relies almost entirely on decoy traps, although other techniques may be used later in the project.
Achievements to date

1. Demonstration of the effectiveness of decoy traps in Denis Island’s habitats (and of the poorer performance of funnel traps, mist nets and ground nooses).
2. In the first two and a half months of the project over 500 mynas have been caught, out of a population estimated at about 1000 birds before trapping began (Jildou van der Woude).
3. Discovery that when groups of traps are placed together, catch rate among traps is variable. Experimental manipulation showed this not due to trap location or possible variation in trap structure or operation, but was due to presence of a specific decoy myna. Elucidation of what constitutes a “super-attractive” myna could improve trapping success.
4. Discovery that iris colour changes as juveniles mature, and that it is variable in adult mynas. Whether this variation represents continuing maturity, and is therefore related to age, or whether it is part of an annual cycle, or reflects mood of an individual, is unknown. Data are being recorded routinely among other features of all mynas caught. If a relation is found between iris colour and attractiveness as defined in section 3 above, this could be a pointer towards selecting attractive decoys.
Throughout May, at the beginning of the eradication, adult mynas were in wing moult, indicating that they were not breeding. In June wing moult was completed and breeding began. This was accompanied by a reduction in the rate at which birds were caught in decoy traps. A number of possibilities could explain this: requirement for different foods by nesting birds, reduced attraction to decoys and traps due to over-use of the decoys and lack of trap maintenance and cleaning, and reduced motivation of the trapper. Decoys were replaced with new birds and traps were overhauled, leading to a recovery in trapping rate. It appears that food choice of the birds did not change and that reduced motivation of the trapper led to lack of attention to the detail of trapping.
6. Comparative failure of funnel traps due largely to occupation of these by turtle doves (especially where food concentrations occur – see below) and crabs, mainly hermit crabs, when traps placed near the beach crest. Denis Island’s populations of Madagascar turtle doves, and also moorhens and mynas, are very high, indicating that the island provides abundant sources of food for them. The main food source concentrations identified are the pig farm, the food store on the northern coast, and the food offered to birds in the garden at the restaurant. Limitation of these food sources to birds would help to reduce the bird populations and would also help to reduce food wastage and its costs.
Lessons learned
We have within two and a half months removed almost half of Denis Island’s population of mynas and have additionally learned much new information about mynas and their behaviour in relation to trapping, including some insights into improvements that may be made. This success suggests that a major reduction in myna numbers on the island is feasible and that eradication should not be ruled out as a possibility and should remain the long-term goal. Decoy trapping is likely to remain the main tool but other techniques may need to be employed as numbers decline, with shooting at the nest being particularly important in the later stages.

Sooty tern project

Previously, sooty terns Onychoprion fuscatus(formerly Sterna fuscata) nested on several island in the Seychelles group but on most islands, especially the smaller ones, colonies became extinct as a result of excessive egg and adult harvesting by people, introduction of exotic predators, and alteration of the habitat Following the successful eradication of rodents and felines early in 2000, Denis island proved to be an ideal site for such re-introduction as these characteristics coupled with food availability and proximity to the supplies proved key aspects that will cater for possible settlement. In addition, an area of ~2ha of open ground with attractant stimuli is available to encourage sooty terns to nest.

As part of Denis Island’s conservation effort, a sooty tern re-colonization programme was initiated in 2008, under the supervision of Professor Chris Feare. Sooties started to arrive on Denis early in June. The ‘wide-awake’ calls could be heard from the lighthouse area, all the way to the dive centre and the sooty tern area. For the month of June, every day was exciting as the situation with the sooty terns was unpredictable. There were days when hundreds of sooties flew over the island, to and fro in search of the ideal landing site and times when several birds landed for minutes and even hours. In the week of June, the island was a marvel to look at; high above in the sky as the colony moved from one end of the island to the next. There was one occasion where hundreds of sooties landed for hours, while some flew around trying to locate the perfect spot on the ground (see photo in side bar).


Friday 2nd July was particularly special to a lot of us who were present on the island. Though it was a rainy morning, there was excitement on the beach in front of the dive centre. More than 300 sooty terns landed on that beach, from the tip in front of the restaurant, right to the high water mark in front of the dive centre. It was unbelievable; having volunteers constantly monitoring their behaviour and movement at the designated area when the birds chose a different spot was quite disheartening for them. Helena and I were very lucky to be at the right place at the right time (See videos below and photos in side bar). It was amazing just to stand and admire those birds which not much is known of their migratory routes and behaviour post nesting season. Since then, the numbers have reduced considerably, with a handful being observed flying around every now and then.

Click on links below for footage of the sooty terns on the beach:

http://www.youtube.com/watch?v=gDJ90OLw1HI

http://www.youtube.com/watch?v=Yrm0yepNK6U

http://www.youtube.com/watch?v=R1TH6Gy8En4