GPS tracking devices reveal foraging strategies of Black-legged Kittiwakes |
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Authors: | Jana Kotzerka Stefan Garthe and Scott A Hatch |
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Institution: | (1) Research and Technology Center Westcoast B?sum, University of Kiel, Hafent?rn 1, 25761 B?sum, Germany;(2) U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, AK 99508, USA |
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Abstract: | The Black-legged Kittiwake Rissa tridactyla is the most abundant gull species in the world, but some populations have declined in recent years, apparently due to food
shortage. Kittiwakes are surface feeders and thus can compensate for low food availability only by increasing their foraging
range and/or devoting more time to foraging. The species is widely studied in many respects, but long-distance foraging and
the limitations of conventional radio telemetry have kept its foraging behavior largely out of view. The development of Global
Positioning System (GPS) loggers is advancing rapidly. With devices as small as 8 g now available, it is possible to use this
technology for tracking relatively small species of oceanic birds like kittiwakes. Here we present the first results of GPS
telemetry applied to Black-legged Kittiwakes in 2007 in the North Pacific. All but one individual foraged in the neritic zone
north of the island. Three birds performed foraging trips only close to the colony (within 13 km), while six birds had foraging
ranges averaging about 40 km. The maximum foraging range was 59 km, and the maximum distance traveled was 165 km. Maximum
trip duration was 17 h (mean 8 h). An apparently bimodal distribution of foraging ranges affords new insight on the variable
foraging behaviour of Black-legged Kittiwakes. Our successful deployment of GPS loggers on kittiwakes holds much promise for
telemetry studies on many other bird species of similar size and provides an incentive for applying this new approach in future
studies. |
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