These are one of my favourite birds and I first saw Tysties at Portpatrick in Galloway back in 1976, they are also the emblem of the Shetland Bird Club.
Unlike the Common Guillemot, they nest in loose colonies among boulders or in crevices which makes counts difficult, back in 2000 around 16,000 individuals were counted which is 10% of the British population. They are prone to oiling, with 729 dead birds recovered after the Esso Bernicia oil spill in the winter of 1978/89. After the Braer oil spill in 1993, 219 birds were found oiled. These incidents had an effect on breeding numbers, with birds lost to otter predation also having an effect. On Fair Isle about 50% of breeding pairs were taken by cats between 1997 and 2000. Add to this predation by Gt Skua, Hoodie crows (eggs) and Brown rats all added up to significant losses.
Numbers in recent years have shown an increase and have almost doubled in population on Mousa from 99 birds in 2007 to 194 birds in 2010, although this increase seems to a halt since. Throughout the islands it is believed that a 20% increase has occurred since 2007
This year breeding is late but adults usually find food easier than the Common Guillemot, favouring Butterfish, with sand-eels only 17% of food brought to chicks.This year we watched a bird fishing in mid Yell, it followed a pattern of going in a circle around the pier and was only disturbed for a short while when a Red throated Diver flew close by
After fledging, young birds form loose flocks and are flightless for a few weeks. Main sites at this time are in sheltered voes around Unst, Fetlar and Yell, Mousa and around Scalloway.
Shetland birds tend to be resident thought to move only around 15 Km from the breeding site.
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