ScotNature in the Seychelles
The Sooty Tern Onychoprion fuscatus is the most numerous seabird in the western Indian Ocean, with an estimated breeding population of 6.2 million pairs. The breeding colonies are scattered throughout the Seychelles archipelago, including about 600,000 breeding on remote Bird Island, the most northerly of the Seychelles island group. Since the present owners bought the Bird Island in 1967, the colony has been protected for most of the time, and the area of available habitat has been increased.
Prof Chris Feare is a world expert on Sooty Terns, having studied them on Bird Island for almost 40 years. However, although, a lot is known on the birds’ breeding ecology and behaviour, knowledge of their dispersal after the breeding season, is limited. Sooty Terns arrive at Bird Island in late May and breed here until September-October, after which they disperse again across the ocean. Chris ringed thousands of Sooty Terns over the years, but there have been only a handful of ringing recoveries. Those in India, Sri Lanka, Northern Australia and at sea off Somalia, suggest that birds disperse widely over the Indian Ocean, but their exact whereabouts remain an intriguing mystery.
So, the idea of studying the dispersal pattern of Sooty Terns, using the latest technology, was born. My husband and I welcomed with great excitement and anticipation, an invitation by Chris to take part in Sooty Tern research on Bird Island. Who wouldn’t?
One of the recently developed methods to study long-distance movements of birds is the use of geo-locators. These devices, attached to the birds (either their back or leg), record the change in light levels at different latitudes and longitudes, as birds cover the globe. Geo-locators are small and very light and therefore can be used on small birds, unlike satellite tags which can be used only on large birds. Using low power technology and data compression, the geo-locators are able to record data for a considerable amount of time. However, birds have to be re-captured in order to retrieve the data. The information stored in the logger can then be downloaded and analysed. Especially designed computer programmes can map the movements of the birds.
Having generated sponsorships and equipped ourselves with 60 geo-locators, the five of us set off to Bird Island. Our team, comprised Prof Chris Fear, Dr Ron Summers (my husband), Christine Larose (a Seychelloise with a love of the island), Amanda Summers (our teenage daughter was left with no choice but to join us on this venture) and myself.
As the Air Seychelles plane dropped us on the tiny island suspended in the middle of the Indian Ocean, we immediately realised what a privileged place we found ourselves in. Never mind the white powder-soft sandy beaches, blue sky and the azure waters that embrace the island – the wildlife was truly astonishing! We were virtually surrounded by Common and Lesser Noddies, nesting on almost every available tree, the beautiful Fairy Terns feeding their chicks on the tiniest of branches, White-tailed Tropicbirds nesting at the bottom of the Casuarina trees, Madagascar Fodies dazzling in the sun in their red plumage (males that is), Seychelles Sunbirds twittering in the bushes and Frigatebirds drifting high on the trade winds. The beaches were dotted with flocks of feeding Turnstones, Grey Plovers, Whimbrels and occasional Crab Plover. Aldabra Giant Tortoises roam the island and, one of them, Esmeralda, is estimated to be over 200 years old. This, apparently, makes her the largest free-ranging tortoise in the world. The proximity to birds and other wildlife, totally untroubled by human presence, was truly magical.
Sadly, as we visited the Sooty Tern colony on our first day, it became apparent that what should have been a peak laying time for the birds, there were only few eggs present in the colony. Even those who initially laid the eggs, deserted them shortly after. As it turned out, this was one of the latest Sooty Tern breeding seasons on record over much of the Western Indian Ocean, from Seychelles down to Madagascar. The reason for this is unknown. One can only speculate that a shortage of food supply could cause such a significant shift in timing of breeding.
Unfortunately, to attach the geo-locators to the birds, we had to catch them on their nests when they incubate the eggs. Although, we gradually developed contingency plans as to overcome this unexpected problem, the decision was made to wait until the birds start laying the eggs. This sudden “holiday” gave us plenty of time to sort out geo-locators, re-design and make proper plastic rings, so the geo-locators could be attached to bird’s legs securely.
It was not too long before the large numbers of eggs appeared in the colony and the much awaited work had begun. Our daily routine involved walking into the colony, catching the birds, measuring, weighing and ringing them, and, finally, attaching geo-locators. Chris was the most experienced on working with Sooty Terns, so he carried out the catching of incubating adults. The rest of us were happy to wait for Chris to deliver the birds, so we could process them. Chris, in the meantime, was making all sort of acrobatic movements while trying to catch the birds. It was not as easy as we initially thought and only with Chris’s experience the mission could succeed – he had to endure though attacks from the adults who pecked vigorously at his ankles, as he walked amongst them. The sound produced by so many birds in the colony was hard on the ears and we all had to wear ear plugs to protect ourselves against it. We could only work at the first light at down and later in the evening, because the heat of the middle of the day was simply unbearable.
Before too long, the first leg of the project was completed and our tropical adventure came to an end. Next year, we will have to re-visit the inland and look for the birds with geo-locators, catch them in the colony and retrieve the devices. We will have to do this again during the incubation period, when birds keep close to their nests, even at human approach. Geolocators are very small and will not be visible on incubating birds. The only way, we will be able to see the ring and the device is when the birds stand up. So, slow movement through a colony will be required with plenty of concentration and careful observation (under siege from the birds and a rain of droppings!). However, once we find the birds and process the data, all the efforts will be rewarded, because the data will provide invaluable information with much greater implications than just fulfilling a gap in our knowledge. We are expecting some revelations!
This project would not be possible without the enthusiast and commitment of Prof Chris Fear, generosity of our sponsors and support of Marie France, the owner of the Bird Island. Marie France commitment to the wellbeing of the island while combining the business with conservation is truly inspiring.
Please note, that after this project is completed, a wildlife/birdwatching tour to Seychelles will be run by ScotNature in 2013, which will include a visit to the magnificent Bird Island and its amazing wildlife.