Activity Budgets and Foraging Ranges of Breeding Common Murres

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Abstract
We used electronic activity recorders to measure flight time, dive time, and time on the water of breeding Common Murres (Uria aalge). During both incubation and chick rearing, about 90% of birds' time away from the colony was spent on the water or diving and 10% was spent flying. The proportion of flight time did not vary with trip duration. During chick rearing, 13.6% of time away from the colony was spent diving, and the proportion of time spent diving tended to decrease with trip duration. Potential foraging ranges calculated from flight times during individual foraging trips showed a concave frequency distribution, and median potential ranges were 37.8 km for incubating birds and 5.4 km for chick-rearing birds. The use of electronic recorders to measure time budgets has broad applications for seabird energetics and foraging ecology and for the assessment of prey availability and abundance.