The influence of coastal water physical processes on the abundance and distribution of seabirds.

摘要

This thesis examines how physical processes associated with coastal waters affect the abundance and distribution of seabirds in these regions at different time-scales. At long time scales, I investigated the effect of physical processes on seabird abundance off Peru as a function of coastal upwelling. At short time scales, I examined the effect of physical processes on seabird distribution in the Bering Sea and Aleutian Islands with respect to particular physical features. In all cases, physical processes appear to determine the biological processes responsible for prey availability to the seabirds.; In the first chapter, I examined the hypothesis that change in the annual population size of guano-producing seabirds (cormorant, Phalacrocorax bougainvillii; booby, Sula variegata; pelican, Pelecanus thagus) is a response to changes in primary and secondary production of the Peruvian upwelling system. I tested this hypothesis by modeling nitrate input through upwelling to the upper layers of the ocean off Peru between 6° S and 14° S using data on wind stress and sea surface temperature.; In the second chapter, I examined the hypothesis that foraging short-tailed shearwaters (Puffinus tenuirostris) aggregate at the inner-front of the southeastern Bering Sea to prey on euphausiids that swarm near the surface. We found enhanced primary production and high density of euphausiids at the front and offshore of the front during summer, but not during spring. My results show that, during summer, the inner-front supports aggregations of euphausiids and their seabird predators.; In the third chapter, I examined the hypothesis that seabird distribution, abundance and diets are different in the eastern and central Aleutian Islands in response to distinct marine environments and energy pathways in each region. We found that distribution, abundance and diets of seabirds could be partitioned into two regions that correspond to marine environments determined by the extent of the Alaska Coastal Current. My study shows major zoogeographical differences in the marine environment between the central and eastern Aleutian Islands. (Abstract shortened by UMI.)