Daily and Annual Habitat Use and Habitat-To-Habitat Movement By Glaucous-Winged Gulls At Protection Island, Washington

Central questions of ecology concern how and why organisms distribute themselves in time and space. Answers to these questions contribute to our understanding of the fitness of organisms and provide baseline information against which to compare future distributions in the face of environmental change. Here we characterize daily and yearly fluctuations in counts of Glaucous-winged Gulls (Larus glaucescens) in 5 connected habitats associated with a large seabird colony in the Salish Sea, Washington State. Daily fluctuations in the 5 habitats differed markedly and were driven by day of year, time of day, solar elevation, tide height, barometric pressure, and ambient temperature. Seasonal peak numbers in all habitats occurred between mid-March and mid-September. No gulls remained on their breeding territories past late September, and few gulls remained on the island between late September and mid-January. Numbers rose steadily from early February to March.