Pursuit-plunging by Northern Gannets (Sula bassana) feeding on Capelin (Mallotus villosus).

Garthe, Stefan, Benvenuti, S. and Montevecchi, W.A. (2000) Pursuit-plunging by Northern Gannets (Sula bassana) feeding on Capelin (Mallotus villosus). Proceedings of the Royal Society of London, Series B : Biological Sciences, 267 . pp. 1717-1722. DOI 10.1098/rspb.2000.1200.

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Abstract

Northern gannets (Sula bassana) are considered to obtain prey usually by rapid, vertical, shallow plunge dives. In order to test this contention and investigate underwater foraging behaviour, we attached two types of data–logging systems to 11 parental northern gannets at Funk Island in the North–West Atlantic. We documented, for the first time to the authors' knowledge, gannets performing long, flat–bottomed, Ushaped dives that involved underwater wing propulsion as well as rapid, shallow, V–shaped dives. The median and maximum dive depths and durations were 4.6 and 22.0m and 8 and 38s, respectively. Short, shallow dives were usually V–shaped and dives deeper than 8m and longer than 10s were usually Ushaped, including a period at constant depth (varying between 4 and 28s with median 8s). Diving occurred throughout the daylight period and deepest dives were performed during late morning. On the basis of motion sensors in the loggers and food collections from telemetered birds, we concluded that extended, deep dives were directed at deep schools of capelin, a small pelagic fish, and we hypothesized that V–shaped dives were aimed at larger, pelagic fishes and squids. Furthermore, these V–shaped dives allowed the birds to surprise their pelagic prey and this may be critical because the maximum swimming speeds of the prey species may exceed the maximum dive speeds of the birds.

Document Type: Article
Keywords: seabirds; pelagic fishes; foraging; diving; predator–prey interaction; swimming speed
Research affiliation: OceanRep > Institute for Marine Science Kiel
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1098/rspb.2000.1200
ISSN: 1471-2954
Date Deposited: 18 Feb 2008 17:24
Last Modified: 03 Apr 2020 08:03
URI: http://oceanrep.geomar.de/id/eprint/1713

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