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A new method to quantify prey acquisition in diving seabirds using wing stroke frequency

Sato, Katsufumi; Daunt, Francis; Watanuki, Yutaka; Takahashi, Akinori; Wanless, Sarah. 2008 A new method to quantify prey acquisition in diving seabirds using wing stroke frequency. Journal of Experimental Biology, 211 (1). 58-65. 10.1242/jeb.009811

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Abstract/Summary

To understand the foraging strategies of free-ranging diving animals time series information on both foraging effort and foraging success is essential. Theory suggests that wing stroke frequency for aerial flight should be higher in heavier birds. Based on this premise we developed a new methodology using animal-borne accelerometers to estimate fine scale temporal changes in body mass of a pursuit-diving, piscivorous seabird, the European shag Phalacrocorax aristotelis. We hypothesized that variations in body mass determined from changes in wing stroke frequency before and after a series of dives would be related to the amount of prey captured. The estimated net gain in body mass during a foraging trip was highly variable, ranging from -30 to 260 g, values that were extremely similar to food loads obtained from shags on the Isle of May in previous years using water-offloading and nest balances. Load sizes estimated using the wing stroke method were strongly and positively related to both cumulative flight time and return flight time. At the trip level load size was unrelated to cumulative dive bout duration and the total amount of time spent underwater. However, highly significant relationships were apparent at the individual bout level with birds showing bigger mass gains following longer dive bouts. Results from this study are therefore extremely encouraging and suggest that changes in body mass determined from changes in wing stroke frequency provide a reliable method of obtaining short to medium term information on foraging effort and success of diving seabirds.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1242/jeb.009811
Programmes: CEH Programmes pre-2009 publications > Biodiversity
CEH Sections: Watt
ISSN: 0022-0949
Additional Keywords: acceleration, data logger, flight, foraging, seabird, Phalacrocorax aristotelis
NORA Subject Terms: Zoology
Ecology and Environment
Date made live: 08 Oct 2008 14:50
URI: http://nora.nerc.ac.uk/id/eprint/3963

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