Comparative foraging ecology of five species of Pacific seabirds : multi-scale analyses of marine habitat use Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5712m853t

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  • Seabirds are an integral component of marine ecosystems, however, because humans typically observe only snapshots of their lives at sea, our understanding of seabird foraging ecology is often limited. A more complete understanding of the ecological roles of seabirds and identification of critical foraging habitats requires the ability to follow individuals at-sea. I analyzed continuous tracking data from blacklegged kittiwakes (Rissa tridactyla) and four species of Pacific albatrosses to determine if foraging time budgets and at-sea movement patterns were associated with prey type (kittiwakes) and remotely sensed environmental variables (albatrosses). Furthermore, I identified variables affecting the spatial scale of search behavior and, for kittiwakes, the effect this has on reproductive success. Black-legged kittiwakes in Prince William Sound, Alaska, increased the number of feeding attempts with increases in the consumption of young-of-year fish and the numbers of feeding flocks encountered, both leading to greater time spent searching for food. Greater search effort translated into longer foraging trip duration (i.e., less frequent nestling provisioning), which was a dominant variable affecting reproductive success. Not surprisingly, area-restricted search activity for kittiwakes occurred over spatial scales two orders of magnitude less than that of short-tailed albatrosses (Phoebastria albatrus; 0.8 km vs. 70 km, respectively). For kittiwakes, the scale of area-restricted search was most prominently associated with prey type. I adapted firstpassage time analysis to model habitat use as a continuous process along a movement path and found that area-restricted search activity of short-tailed albatrosses was greatest along the continental shelf break and slope within regions of higher gradients of depth and chlorophyll a. Wind speed also was an important variable affecting albatross movements. By capitalizing on ocean surface wind and wave energy, albatrosses efficiently travel over vast expanses of the world’s oceans. I analyzed albatross aerodynamics and satellite remote sensing data to demonstrate that the four species of albatrosses inhabiting the North and Central Pacific Ocean exhibit differences in flight morphology that are generally consistent with respect to prevailing wind and wave conditions encountered. Some individuals, however, ventured into regions of apparently suboptimal wind and wave conditions to presumably exploit preferred foraging opportunities.
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  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2006-04-26T14:56:52Z (GMT) No. of bitstreams: 1 Suryan_Dissertation_14Apr2006.pdf: 1945890 bytes, checksum: d2b2bc0473e9bd93173c0704e566aa3c (MD5)
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