As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Thursday 6 September 2018

Color vision makes birds of prey successful hunters




Date:  August 29, 2018
Source:  Lund University
In many cases it is the colour of the prey that helps predatory birds to detect, pursue and capture them. In a new study, biologists at Lund University in Sweden show that the Harris's hawk has the best colour vision of all animals investigated to date -- and in certain situations, even better than humans. The findings may help to protect threatened birds of prey against hazards such as wind turbines and power lines.
"It's fascinating. I did not think that colour vision would be of such significance, rather that birds of prey simply have better visual acuity than humans and that was the reason they detect objects so early and at a great distance. However, colour is of considerable importance," says Almut Kelber, biologist at Lund University.
Normally, the size of the eyes determines optical resolution and thus what people or animals can see. The bigger the eyes, the higher the resolution. The size of the eyes in turn is usually linked to body size. Large body, large eyes; small body, small eyes. Particular to birds is a poor ability in general to see contrasts between different objects. Their contrast vision is almost ten times lower than ours.
However, there are exceptions, and the Harris's hawk (Parabuteo unicinctus) is one of them. The study by the Lund biologists shows that if an object is not distinguishable from the background and the colour is approximately the same, it is more difficult for a bird of prey than a human to detect it. If, on the other hand, the object has a different colour than the background, the Harris's hawk can detect it at twice the distance compared to human vision.
"It's exciting! The hawk weighs less than one kilo and has small eyes. Nonetheless, it can see many times better than us, even though it is so small and light," says Simon Potier.

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