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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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