Poor diet contributing to Sooty Tern decline

04/02/2019

The observed population crash in a Sooty Tern colony located on Ascension Island, one of the UK Overseas Territories (UKOTs), is partly due to poor diet, research led by the University of Birmingham has found.

The findings provide fresh evidence of the fragility of marine ecosystems and lend weight to the scientific case for creating the Ascension Island Ocean Sanctuary (AIOS), set to be one of the largest fully protected reserves in the Atlantic Ocean.

The most numerous seabird of tropical waters, Sooty Tern is an abudant species. The colony on Ascension Island is the largest in the entire Atlantic Ocean. However its population has declined from several million in the middle of the last century to just a few hundred thousand today. A team based in the University's School of Biosciences believes the birds' plight is closely linked to changes in populations of predatory fish, such as tuna. The terns follow these large fish across vast expanses of ocean to feed on the small fish driven to the surface as they hunt.

The terns had been expected to benefit from conservation work carried out on the island between 2002 and 2004 by the RSPB. This involved a feral cat eradication scheme in a bid to restore nesting populations of seabird species, including the rare Ascension Frigatebird.

However, while many seabird species subsequently began to thrive, the tern population did not recover as expected and the Birmingham team, together with researchers from the University of Exeter, the Ascension Island Government Conservation Department (AIGCD) and the Army Ornithological Society (AOS), set out to find out why.

Dr Jim Reynolds, lead author on the paper, commented: "We believe that a number of factors might influence the size of the breeding population of sooty terns on the island but we wanted to understand such factors in greater detail, resulting in causal explanations of the tern population decline over the past 60 years."

Continued

Frigate birds reappear on Ascension Island after 180 year absence

A UK bird has been found breeding again on a remote island, almost 180 years since it was last recorded there.

December 2012. Two Ascension frigatebirds were spotted sitting on nests on Ascension Island, a UK Overseas Territory. The species has previously been confined to the outlying Boatswain Bird Island, which is just 1km², for decades after taking refuge there when feral cats overran the main island of Ascension.

Millions killed by cats
The seabird population on the tropical UK Overseas Territory, previously numbering into the tens of millions, was devastated by the cats which were introduced onto the island in the early 19th Century to control introduced rats and mice. The RSPB began a project to remove feral cats on Ascension Island in 2002. The project was supported by funding from the Foreign and Commonwealth Office and the island was formally declared feral cat free in 2006.

Globally threatened
The Ascension frigatebird is a globally threatened species found nowhere else in the world. It is one of the 33 Globally Threatened British Birds found in the UK's Overseas Territories, and is considered Vulnerable to Extinction by the IUCN.

Dr Tim Stowe, the RSPB's International Director, said: "This is the news we have been waiting for since starting the project more than a decade ago. Many species on the UK Overseas Territories are threatened by non-native species and this project marks a landmark in conservation. Ascension is the largest, inhabited island where feral cat removal has been attempted and proved successful. What a wonderful Christmas present."

The discovery was made by members of the Army Ornithological Society, together with members of the Ascension Island Government's Conservation Department.

Read on:  http://www.wildlifeextra.com/go/news/ascension-frigate.html