| Summary: | Thick-billed Murres (Uria lomvia) breeding in the Canadian Arctic are restricted to a small number of colonies, all comprising more that 10,000 pairs. Five of these colonies are scattered through Hudson Strait. We collected adult breeders at three of the colonies - Digges Island, Hantzsch Island, and Akpatok Island - and compared wing and bill measurements and body weights to look for inter-colony differences. Significant inter-colony differences were present for all measurements and a discriminant function analysis showed that some individuals fall completely outside the range of variation for the other colonies. Because of the presence of the Laurentide ice-sheet over Hudson Strait, the present colony sites could not have been occupied for more than 10,000 years. If the observed differences reflect differences in genotype then their evolution must have occurred over this period.Key words: Thick-billed murre, Uria lomvia, phenotypic variation, Hudson Strait, evolution Mots clés: Marmettes de Brunnïch, Uria lomvia, variation des phénotypes, détroit d'Hudson, évolution
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