Abstract
AbstractGreat Cormorants Phalacrocorax carbo are regarded as visually-guided, pursuit-dive foragers, so it would be expected that they have excellent vision much like aerial predators, such as hawks which detect and pursue prey from a distance. However, my research shows that underwater the visual acuity of Cormorants is surprisingly poor (in fact, similar or worse than unaided humans under water) and very inferior to that of aerial predatory birds. I suggest that Cormorants are able to detect typical prey items only at close range and conclude that cormorants are not the aquatic equivalent of hawks. It seems that their efficient hunting involves the use of specialised foraging techniques which employ rapid neck extension to capture prey that cormorants flush from hiding places; much like the foraging techniques of herons. Cormorants seem to be hunting an “escaping blur”. Like herons, the eye movements and visual fields of cormorants allow visual scanning for escaping prey in a wide arc about the head. The ability of cormorants to see prey held in the mouth may help to aid its identification when it is brought to the surface before swallowing.
Highlights
They can detect information of which we are totally unaware unless we use technology to detect it
One of the most prominent people to recognise this in the world of birds was Niko Tinbergen, who won a Nobel Prize in recognition of his work in this area
We popularly think that vision is the dominant sense of birds, and may think of birds as “A wing guided by an eye”, but that picks out just one aspect of a bird’s life
Summary
One of the most prominent people to recognise this in the world of birds was Niko Tinbergen, who won a Nobel Prize in recognition of his work in this area. We popularly think that vision is the dominant sense of birds, and may think of birds as “A wing guided by an eye”, but that picks out just one aspect of a bird’s life. Many birds make their living by diving and finding prey: what do we know about their underwater world?
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