Kittiwakes Decline on Shetland Islands

from British Birds

Kittiwakes, one of the most loved of seabirds, are in serious decline on the Shetlands according to a new report published in the March issue of the monthly journal British Birds (Martin Heubeck - 95: 118-123).

Careful counts at breeding colonies over the last twenty years show a decline of 70% on the main Shetland colonies. On Fair Isle, a few miles south of the main islands, the decline did not start until about 1990 but the colonies are now down to 8,204 breeding pairs from 19,340 in 1988. This is almost exactly a third of the Shetland breeding population - Fair Isle had about a quarter of Shetland's Kittiwakes in 1981.

Martin Heubeck, the author of the report, spends a lot of time each summer in a small inflatable carefully counting the Kittiwake nests in the colonies round the coast. He is very sad that many of the traditional sites, where the birds had bred for years, are now deserted.

Two reasons are put forward for the loss. The birds feed on sand eels and switch from the one year-old fish to the same years as the breeding season progresses. Unfortunately the fish's behaviour has changed and often they are hidden in the sand when the birds need them.

This has affected some other species too and the lack of seabirds flying around with sand eels in their beaks has stopped the aggressive Great Skuas from stealing their food. They have therefore changed to direct predation on the seabirds - and particularly the Kittiwakes. Many of the colonies which are still in existences, and certainly a lot of those which are doing relatively well, are in more sheltered areas where the Great Skuas find it more difficult to predate the breeding birds.

Kittiwakes, Rissa tridactyla, are charming and small dove grey cliff-nesting gulls. Their name comes from their call. About 10% of Britain's breeding population and rather more than 1% of the North Atlantic population.

Great Skuas, Catharacta skua, are big brown gull-like birds with a white flash in their wings. They are rare in most areas but Shetland has more than 40% of the world population! They are therefore of great conservation interest even though they are very destructive of the Kittiwakes!

Page Author: Chris Mead, Hilborough, Norfolk chris.mead@zetnet.co.uk