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."
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