A LONG-TERM study of a large puffin colony on Fair Isle in Shetland has caused “considerable concern” after showing that breeding numbers have halved to 10,000 individuals.
The study, published by the scientific journal, Plos One, covers a period of nearly 30 years, starting in 1986.
Dr Will Miles of the Fair Isle Bird Observatory found that the most likely cause of the decline was failure of young birds to return to the island to breed.
Dr Miles said: “We don’t know exactly why they would fail to return to Fair Isle and settle to breed but it may be due to declining local fish stocks and poor feeding conditions for seabirds in Shetland waters.
“It is very difficult to find out exactly what happens to immature puffins after they have fledged because of the vast sea areas and the problems of tracing them within other colonies.”
The study showed that since the 1980s the quantities of fish brought ashore by adult puffins for their chicks declined substantially.
Dr Miles also looked at the possible impact of great skuas on the puffin colony. The number of these seabirds, also known as ‘bonxies,’ has increased by around 300 per cent on Fair Isle in the same period, to over 400 breeding pairs in 2014, and in the UK in recent years, as well as eating fish, they’re known to have fed on seabirds.
He said he was surprised to find that, despite this increase, adult puffin survival on the island has remained high and stable over the 30 years.
“It seems adult puffins on Fair Isle are pretty good at avoiding skuas and do not get heavily predated by them,” added Dr Miles.
Seabird populations around the UK are changing with many drastically declining.
Dr Mark Bolton of the Royal Society for the Protection of Birds was an advisor to the Fair Isle puffin study. He said: “The UK supports internationally important populations of puffins, which are among our best-loved seabirds. Whilst visitors to Fair Isle can still enjoy the spectacle of thousands of birds, the severe decline reported in this study is cause for considerable concern.
“This decline reflects the recent change in the IUCN pan-European conservation status of puffin to ‘endangered.’”
The work reported in the study is important, because it illustrates the complex interplay among many factors that may contribute to declines of seabirds, and the need for long-term studies to diagnose cause and effect. Such studies are essential to ensure adequate management of the marine environment to safeguard the future of our seas, and the species which depend on them.
Fair Isle is Britain’s most remote inhabited island and lies between Orkney and Shetland. It is one of only four sites chosen by the UK government, through the Joint Nature Conservation Committee, for intensive monitoring of seabirds. Dr Miles formerly took part in the monitoring activity, as an assistant warden at the bird observatory.
He is now based at the University of Aberdeen and employed by the Fair Isle Bird Observatory Trust.
Puffins are very long-lived, with some individuals reaching 30 years of age. Young puffins usually start to breed when they are five or six years old. Prior to breeding, these immature birds prospect colonies for mates and nest sites.