The objective of our mission was to capture roosting seabirds on St François island and attach satellite tracking devices to them – quite a unique undertaking, as most tracking studies have focussed on breeding colonies where it is possible to check the attachment of the device and even retrieve it at a later date. Studying a non-breeding colony presents more of a challenge, but the resultant data should provide insight into their flight movements and the secrets of their preferred feeding grounds at sea.
In the darkness, we walked through the maze of mangroves inside St. François lagoon; circles of light from our headtorches illuminating the murky water through which we waded. Every direction we shone the torches, mullet leapt from the water in surprise, and we considered what other creatures were surely lurking around us. Two conservation biologists and consultants, ICS board member, Dr. Gerard Rocamora, and former Alphonse Conservation Officer, Josep Nogués, had arrived from Mahé to the Alphonse ICS offices the day before and spent the afternoon intently checking and testing the devices. Conservation Ranger Chris Narty, George Curd and myself (the current Alphonse Conservation Officers) joined them in this seabird expedition to St François.
Even at our campsite, the Fou Bet filled the trees like decorations, competing for the most comfortable roost spots and arguing in hoarse rasping croaks. Over the first two nights, working until early in the morning, we successfully caught several birds and carefully attached the small devices. The method for attachment depends upon the target species. For the Greater Frigatebirds (Fregata minor) – known as Gran Fregat in Creole - we used a simple harness which strapped around the bird’s chest and wings and under its armpits. The Fou Bet require a more complicated procedure; as these birds are divers, the device needs to be robust against impact with water. The four middle tail feathers are selected, and the satellite tracker is taped to these, with care given to the solar panel which needs to be left completely exposed for this technology to have the best chance of transmitting properly (we are expecting to get around six weeks’ worth of movement data for these birds). We are expecting a longer duration of transmission - up to six months or more - to come from the Gran Fregat, as they are unable to dive for their food due to a lack of oil in their feathers, relying instead upon surface fishing and piratical attacks on other species to steal their catch. ICS monitors seabird populations closely in the islands that fall under its mandate, as they are important indicators of the overall ecosystem health.
During the last nights, we spent time capturing and ringing more Red-footed boobies in order to collect over thirty individual blood samples. This will serve for an analysis conducted at the University of La Réunion to determine the genetic affinities of the boobies roosting on St François. This should help us to answer one of the research questions of the tracking study; to determine from which breeding colonies the Red-footed boobies roosting on St François come from. Soon after this expedition, the resident ICS team discovered for the first time ever - a Red-footed booby nest, with a chick estimated at just a couple of weeks old. If other birds follow suit, then St. François could become the fifth island in the Seychelles to host a breeding colony for this species.
St. François, part of the Alphonse Group and at the southern tip of the Amirantes chain, is one of the few wild places left on earth, where creatures can take refuge from the brutality of human impact elsewhere. All 8 tracking devices were successfully deployed on roosting Fou Bet and Gran Fregat, and now we wait to see where the birds travel over the coming weeks. This information will illuminate an area of seabird ecology that is still poorly understood at this location, and will prove useful in the determination of effective MPAs.