Mixed Picture In Latest Scilly Bird Survey
The latest survey of Scilly’s wild birds has produced a mixed picture, with some species doing well while others have disappeared altogether.
It’s the third year that Bob Dawson has collected data for the Breeding Bird Survey, which has been run since 1994 by the British Trust for Ornithology.
He takes measurements by walking a 1 km square around Troytown and Periglis on St Agnes, one of over 3,000 sites across the UK that are surveyed twice a year.
And the data, which in the past has also been collected by Will Wagstaff and John Hale, has been revealing.
Bob says cuckoos, which were common here 20 years ago, have completely disappeared.
In the 1990’s, there were up to five cuckoos recorded at the site at any one time, but none were found this year.
Bob says there’s a similar trend across the whole country although the reason for the decline isn’t clear.
There’s a theory it could be linked to lower numbers of the hairy caterpillars that the birds feed on before laying their eggs.
But an 80% drop in the numbers of rock pippets is “totally unexpected,” says Bob.
There’s no obvious reason, he says, because their habitats and food supply haven’t changed a lot in the past two decades, although some nesting sites have been lost to coastal erosion.
There’s good news though, with some birds doing rather better here than their cousins on the mainland.
Songbirds like thrushes and wrens have remained fairly constant.
But Bob says the real success story is the greenfinch and goldfinch.
Numbers here have soared, at a time when the population on the mainland is being hit by a nasty disease passed between the birds on their beaks.
Bob says many woodland-type birds started to move to Scilly as the hedgerows, planted as windbreaks around the flower fields, started to mature.
And now, many aren’t even bothering to migrate as usual to the Continent or North Africa.
Bob says the ready availability of food, especially on bird tables, is enticing them to remain here over the winter.