Factors determining seasonal changes in attendance at colonies of the thick billed murre uria lomvia
Gaston, A.J.; Nettleship, D.N.
Auk 99(3): 468-473
ISSN/ISBN: 0004-8038 DOI: 10.2307/4085926
A comparison of the interyear variation in attendance patterns of thick-billed murres (U. lomvia) with the variation in egg size and chick growth rates suggests that the number of birds in attendance at a murre colony at any time during the breeding season is determined principally by the availability of food in surrounding waters. This effect operates mainly through the behavior of a large floating population of prospectors. When food is abundant, numbers on the cliffs will be high because birds have plenty of time to spare. Conversely, when food is scarce, numbers will be low because birds must devote most of their time to feeding. Implicit in the hypothesis is the assumption that birds strive to maximize the amount of time that they spend at the breeding colony in order to improve their chances of acquiring and retaining a breeding site.