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Underwater wingbeats extend depth and duration of plunge dives in northern gannets Morus bassanus

Ropert-Coudert, Yan; Daunt, Francis; Kato, Akiko; Ryan, Peter G.; Lewis, Sue; Kobayashi, Kaori; Mori, Yoshihisa; Gremillet, David; Wanless, Sarah. 2009 Underwater wingbeats extend depth and duration of plunge dives in northern gannets Morus bassanus. Journal of Avian Biology, 40 (4). 380-387. 10.1111/j.1600-048X.2008.04592.x

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Abstract/Summary

Plunge-diving is a specialised hunting tactic used by some avian predators to overcome the high buoyancy encountered near the water surface and surprise prey. However, plunge-diving is effective only to a certain depth; to access deeper prey, birds need to use an additional method of propulsion, e.g. wings or feet. We used miniature accelerometers to record the details of the aerial and underwater phases of plunge dives by northern gannets Morus bassanus. Birds never reached depths >11 m using the momentum of the aerial part of the plunge dive and had to flap their wings underwater to gain additional depth. A biomechanical model demonstrates that little additional depth can be obtained from momentum alone when initiating a plunge from heights >40 m. Thus, the additional energy required to attain greater starting heights is not rewarded by reaching significantly greater depths. However, by using their wings underwater, gannets were able to more than double the depth attained (up to 24 m). It appears that prey may be captured by surprise in the first 10 m of the water column, whereas wing-propelled pursuit is required to catch prey at deeper depths, a strategy likely to be used only for prey of sufficient profitability to justify the cost of flapping the gannet's large wings underwater. Our study demonstrates the importance of understanding the constraints placed on predators by the physical environment when interpreting predator-prey interactions.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1111/j.1600-048X.2008.04592.x
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity > BD Topic 1 - Observations, Patterns, and Predictions for Biodiversity > BD - 1.4 - Quantify and model interactions to determine impacts ...
CEH Sections: Watt
ISSN: 0908-8857
NORA Subject Terms: Zoology
Ecology and Environment
Related URLs:
Date made live: 06 Aug 2009 09:46
URI: http://nora.nerc.ac.uk/id/eprint/7664

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