| Summary: | Typically, red-legged kittiwakes used ledges 1 dm deep; northern fulmars, black-legged kittiwakes, and thick-billed murres used ledges of an intermediate 2-4 dm depth; red-faced cormorants used ledges 3-6 dm deep; and common murres occurred singly on shallow ledges or in groups on deeper ledges. Fulmars and murres, which did not build nests, used nearly horizontal ledges exclusively; the nest-building species occurred on a wider range of slopes. Only red-legged kittiwake regularly used ledges with over 50% cover by overhanging cliff within 5 dm of the ledge. Classification of the measured ledges of the cormorant, the 2 kittiwakes, and thick- billed murre by a discriminant function analysis revealed significantly greater overlap than expected between the species pairs of cormorant with thick-billed murre, black-legged with red-legged kittiwake, and black-legged kittiwake with thick-billed murre.-from Authors
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