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1 February 2011 Evidence for Foraging-Site Fidelity and Individual Foraging Behavior of Pelagic Cormorants Rearing Chicks in the Gulf of Alaska
Jana Kotzerka, Scott A. Hatch, Stefan Garthe
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The Pelagic Cormorant (Phalacrocorax pelagicus) is the most widespread cormorant in the North Pacific, but little is known about its foraging and diving behavior. However, knowledge of seabirds' foraging behavior is important to understanding their function in the marine environment. In 2006, using GPS dataloggers, we studied the foraging behavior of 14 male Pelagic Cormorants rearing chicks on Middleton Island, Alaska. For foraging, the birds had high fidelity to a small area 8 km north of the colony. Within that area, the cormorants' diving activity was of two distinct kinds—near-surface dives (1–6 m) and benthic dives (28–33 m). Individuals were consistent in the depths of their dives, either mostly shallow or mostly deep. Few showed no depth preference. Dive duration, time at maximum depth, and pauses at the water surface between consecutive dives were shorter for shallow dives than for deep dives. The cormorants made dives of both types throughout the day, but the frequency of deep dives increased toward evening. Maximum foraging range was 9 km; maximum total distance traveled per trip was 43.4 km. Trip durations ranged from 0.3 to 7.7 hr. Maximum depth of a dive was 42.2 m, and duration of dives ranged from 4 to 120 sec. We found that Pelagic Cormorants at Middleton Island were faithful to one particular foraging area and individuals dived in distinct patterns. Distinct, specialized foraging behavior may be advantageous in reducing intra- and interspecific competition but may also render the species vulnerable to changing environmental conditions.

© 2011 by The Cooper Ornithological Society. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website,
Jana Kotzerka, Scott A. Hatch, and Stefan Garthe "Evidence for Foraging-Site Fidelity and Individual Foraging Behavior of Pelagic Cormorants Rearing Chicks in the Gulf of Alaska," The Condor 113(1), 80-88, (1 February 2011).
Received: 19 August 2009; Accepted: 1 July 2010; Published: 1 February 2011

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