Ascension Island, a great place to sea-birds!

We’re very happy to welcome Becky Taylor back to the blog this week. Becky is a PhD Candidate at Queen’s University and today she tells us more about her fieldwork experiences on Ascension Island. You can also check out her last post here.

Ascension Island is truly a weird and wonderful place to visit! If you are wondering where on earth this place is, see my previous blog for a brief history and overview of this unique, remote island. As an Important Bird Area for its incredible seabird diversity (according to Birdlife International), I thought it would be great to dedicate a whole blog to talk about the seabirds of Ascension Island.

But why was I actually there? I am studying the band-rumped storm-petrel (Oceanodroma castro) for my PhD, a seabird found on Ascension and St Helena, for which I needed samples. Ascension Island is an incredible place to see seabirds. However, they are largely restricted to breeding on Boatswain Bird Island just off the coast of Ascension due to the introduction of rats and then cats after human colonisation. This decimated the seabirds breeding on the mainland, including the endemic Ascension Frigatebird which became completely restricted to Boatswain Bird.

Boatswain Bird Island

While I was on Ascension I was lucky enough to tag along with the Ascension Island Government Conservation team to help out with their monitoring of some of the species of seabird, as well as the storm-petrels (or ‘stormies’ as they are known). One charismatic species we would visit is the masked booby. This is one of the seabirds that is still breeding on the mainland, and so we would venture to their nests and try and find out what they were sitting on. This basically involved poking at them with a giant stick to see what they had underneath and to make them call (to find out if it was a male or female). This may sound rather mean, but they plonked themselves straight back on their nests when we were done!

A masked booby chick and an adult on its nest with a hatched chick and un-hatched egg

Similarly we would go and do the same to the brown booby nests on another part of the island, poking them to see what they had on the nest. Both booby species lay two eggs, though only one will survive to adulthood. The first hatched will expel their younger sibling from the nest to ensure their survival!

Brown booby chick and an adult on its nest

But one of the most incredible seabird species found on Ascension Island is the endemic Ascension frigatebird.

The Ascension frigatebird male with red gular sac visible, and female in flight, showing the sexual dimorphism in this species

Listed as Vulnerable on the IUCN Red List, this species is undergoing a conservation success story! The decision was made to eradicate the cats which had expelled this charismatic seabird from breeding on the mainland. In 2006 this was achieved, and in the last few years they have finally started breeding on Ascension itself once again. I was lucky enough to see the fledglings from this year’s mainland nests, 5 in total.

Two Ascension frigatebird fledglings on their neighbouring nests

Amongst the other seabird species on the island, two of my favourites were the fairy tern and the yellow-billed tropicbird. The fairy terns are gorgeous white and seem to dance around in the wind above your head as you walk. Apart from when I would try and get a nice close up picture, then sure enough they would disappear! The yellow-billed tropicbirds also seem to have an elegant quality about them. We went around checking their nests too, though you definitely don’t poke these birds with a giant stick, as they are much more likely to abandon their nests. We would just stand back and admire these long-tailed seabirds from a respectable distance.

Fairy tern in flight

Yellow-billed tropicbird on its nest

But, of course, my favourite seabird species (and by no coincidence the one I was there to study) was the band-rumped storm-petrel. We would catch these small birds using a mist net in a place known on the island as ‘Storm Gully’.

Boatswain Bird Island as seen from ‘Storm Gully’, our mist netting site

These birds are nocturnal, and so we would set up the nets and wait in the dark. Unfortunately if the moon was too bright they would see the net and swoop out of the way, but most of the time we caught a steady stream of birds. Once caught, morphometric measurements and blood samples were taken (for my DNA analysis), before being set free to fly across back to their nests on Boatswain Bird Island. And, aside from having a giant rat run across my chest while trying to get some rest one night, the wait was always worth it to see these amazing seabirds!

The small band-rumped storm-petrel having morphometric measurements taken.

Becky completed her BSc in Biology at the University of Bristol, UK in 2010, and then worked for the conservation charity Wildscreen on their ARKive website for two years before deciding to undertake her MSc at the University of Exeter, UK. She started her PhD at Queen’s University in September 2013. She is currently researching the genomics of the evolution of seasonal populations of the band-rumped storm-petrel (Oceanodroma castro), and aims to create a comprehensive phylogeny of this cryptic species complex.