The ecologically important nesting seabirds of the Alphonse Group, Seychelles

The Island Conservation Society (ICS) is an NGO which has the mandate to conserve and monitor the dynamic and vulnerable island ecosystems of six of the Seychelles Inner and Outer Island group, namely, Alphonse, Aride, Cosmoledo, Desroches, Farquhar and Silhouette. Each Conservation centre has a small team of dedicated and experienced conservationists that work with the Island Conservation Society Head Office, Island Development Company (IDC) and tourism establishments to achieve their collective conservation goals.

The Alphonse Island group is comprised of three sand cays, each dominated by unique habitats that are ideal for nesting and roosting seabirds. The resource-rich lagoons surrounding each island and the abundant life in the deep oceans provide an abundance of food for seabirds. ICS has been monitoring the population numbers and breeding success of all nesting seabird species in the Alphonse Group, including Red-footed boobies, Wedge-tailed shearwaters and Black-naped terns since they began working on Alphonse in 2007.

Until 2019, Red-footed boobies roosted in large numbers of up to 20000 individuals on St. Francois Island throughout the year but had never nested in the Alphonse Group. For several years, conservationists were so convinced that this was the perfect place for the red-footed boobies to nest that they considered using artificial red-footed boobies placed on artificial nests in an attempt to encourage the large population to start nesting there. But before they got a chance to test this theory, one pair of Red-footed boobies decided for themselves and laid an egg high up in a Casuarina tree in 2019. Since then, the number of nesting pairs has increased every year with 16 currently active nests. This is great news because it means that this species is showing signs of recovery after many years of population decline.

Wedge-tailed shearwaters nest in small burrows in the sand or soil, making their defenceless chicks particularly vulnerable to predators such as rats and cats. Despite the predation pressure from these alien invasive species present on Alphonse Island, this seabird nested here in small numbers for many years before being given a helping hand by the ICS conservation team. In 2017, they placed rat and cat traps around the shearwater colony to protect the chicks during the breeding season. This innovation has been incredibly successful, with the number of chicks leaving the nest at the end of the breeding season going up from only 9 before the traps were placed to over 50 in the last two years.

Although the shearwater colony on Alphonse is increasing, the colony on Bijoutier is facing a different challenge. This small island has been shifting several meters in an easterly direction every year for more than 20 years, losing its ideal nesting habitat as it moves. As a result, the number of nesting pairs has gone from 80-90 to only 20-25 in the last few years. As the sand builds up on the new, and eastward side of the island, it presents opportunities for other species that thrive on long beach crests such as sea turtles.  As the pioneer vegetation continues to establish, however, the amount of nesting habitat for the wedge-tailed shearwaters will hopefully start to increase.

St. Francois is also an important nesting area for the Black-naped tern, making up 5% of the national breeding population. Black-naped terns lay their camouflaged eggs directly onto the sand which makes them particularly vulnerable to predation and disturbance. St. Francois has ideal nesting habitat for this species because it is free of invasive species such as rats and cats and also has very limited human activity, especially on the beaches. The ICS conservation team regularly visits St. Francois throughout the year and monitors the breeding success and behaviour of this species.  Although variable, the breeding population seems to be stable.

As the threats from climate change become more apparent, such as rising sea levels and increased strength of storms, sea birds are some of the species most vulnerable. By keeping track of population size and breeding success, the ICS team can stay ahead of any threats that may arise, allowing these incredible birds to not only survive but thrive.

Contributed by Kaeleah Andrews, Assistant Conservation officer of Alphonse Group