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Colony interchange in Baltic Guillemots Uria aalge
Lyngs, P. (1993) Dansk Orn. Foren. Tidsskr. 87:247-250
Introduction
Very little is known about colony interchange in Guillemots Uria aalge, and indeed in most alcids. An auk rarely if ever change colony when it has first started breeding, but emigration and immigration of young birds may have significance for alcid populations, as can be deduced from cases where colony growth has exceed the populations intrinsic rate of increase (e.g. Hudson 1985). However, apart from recapture data on Puffins Fratercula arctica (Harris 1983, Harris & Wanless 1981) little evidence of movements between colonies has been published.

This paper presents recapture data on Baltic Guillemots ringed as chicks, and shows that intercolony movements occur regularly. Some figures differ from those formerly given by Lyngs (1992a) because new data has become available, but the conclusions remain the same.

The Baltic Guillemot population numbered around 13000 breeding pairs in the mid-1980s (SOF 1990, Lyngs 1992a) with more than 90% in three colonies: about 7500 pairs at Stora Karlso, 2500 pairs at Lilla Karlso and 2000 pairs at Graesholmen. The population has grown throughout this century (Hedgren 1975); during the 1970s and 1980s the main colonies increased by 2-4% annually and some small colonies by 10-14% annually (Lyngs 1992a). Most of the Baltic Guillemots winter in the Baltic Sea and in inner Danish waters (Anon, 1991, Lyngs 1992a)

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