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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