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.