Flexible time budgets in breeding common murres: buffers against variable prey abundance
Burger, A.E. & Piatt, J.F. (1990) Stud Avian Biol 14:71–83
We report on a 4-year study of the relationships between parental behavior of Common Murres (Uria aalge) and the relative abundance of their principal prey, capelin (Mallotus villosus), at Witless Bay, Newfoundland. Capelin comprised 89% of the prey fed to murre chicks. Capelin abundance and the density of their schools, measured with hydroacoustic surveys, varied significantly within and between each of the murres’ breeding seasons, by up to 10-fold. Despite this, the feeding rates of chicks (average 0.28 fish/chickh) did not vary significantly between years, and were not depressed by intraseasonal capelin variations. Adult murres compensated for periods of low capelin abundance by taking more of other fish, particularly sandlance (Ammodytes sp.), and by spending more time at sea. Chick survival (average 93%) did not vary significantly between years. Chick feeding rates and parental resting time at the colony were not strongly affected by weather, sea conditions or chick age. We suggest that with moderate prey abundance, variable time budgets of adult murres would buffer the effects of temporal and spatial prey variability so that chick feeding rates would remain relatively constant. Under such conditions chick growth and survival might not reflect food availability.
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