Vision and the foraging technique of Great Cormorants Phalacrocorax carbo: Pursuit or close-quarter foraging?

Martin, Graham R., White, Craig R. and Butler, Patrick J. (2008) Vision and the foraging technique of Great Cormorants Phalacrocorax carbo: Pursuit or close-quarter foraging?. Ibis: The International Journal of Avian Science, 150 3: 485-494. doi:10.1111/j.1474-919X.2008.00808.x

Author Martin, Graham R.
White, Craig R.
Butler, Patrick J.
Title Vision and the foraging technique of Great Cormorants Phalacrocorax carbo: Pursuit or close-quarter foraging?
Journal name Ibis: The International Journal of Avian Science   Check publisher's open access policy
ISSN 0019-1019
Publication date 2008-07
Sub-type Article (original research)
DOI 10.1111/j.1474-919X.2008.00808.x
Volume 150
Issue 3
Start page 485
End page 494
Total pages 10
Place of publication Oxford, United Kingdom
Publisher Blackwell Publishing
Language eng
Subject 0608 Zoology
Abstract Predatory diving birds, such as cormorants (Phalacrocoracidae), have been generally regarded as visually guided pursuit foragers. However, due to their poor visual resolution underwater, it has recently been hypothesized that Great Cormorants do not in fact employ a pursuit-dive foraging technique. They appear capable of detecting typical prey only at short distances, and primarily use a foraging technique in which prey may be detected only at close quarters or flushed from a substratum or hiding place. In birds, visual field parameters, such as the position and extent of the region of binocular vision, and how these are altered by eye movements, appear to be determined primarily by feeding ecology. Therefore, to understand further the feeding technique of Great Cormorants we have determined retinal visual fields and eye movement amplitudes using an ophthalmoscopic reflex technique. We show that visual fields and eye movements in cormorants exhibit close similarity with those of other birds, such as herons (Ardeidae) and hornbills (Bucerotidae), which forage terrestrially typically using a close-quarter prey detection or flushing technique and/or which need to examine items held in the bill before ingestion. We argue that this visual field topography and associated eye movements is a general characteristic of birds whose foraging requires the detection of nearby mobile prey items from within a wide arc around the head, accurate capture of that prey using the bill, and visual examination of the caught prey held in the bill. This supports the idea that cormorants, although visually guided predators, are not primarily pursuit predators, and that their visual fields exhibit convergence towards a set of characteristics that meet the perceptual challenges of close-quarter prey detection or flush foraging in both aquatic and terrestrial environments.
Keyword Great cormorant (Phalacrocorax carbo )
Feeding ecology
Eye movements
Prey capture
Q-Index Code C1
Q-Index Status Provisional Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biomedical Sciences Publications
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Created: Tue, 12 Jan 2010, 12:50:02 EST by Michael Affleck on behalf of Faculty of Science