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Feb 06, 2014 08:42 AM EST

Jackdaws Use Bright Eyes to Protect Nests and Ward off Enemies, Study

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Researchers from the University of Cambridge and University of Exeter have discovered a unique form of communication in birds.

Jackdaws, predominantly found in Europe, North Africa and Western Asia, use their bright white eyes to keep their rivals at bay and to discourage them from coming near their nests. Jackdaws usually build their nests in natural cavities of trees.

It is a well-established fact that humans use eyes to communicate with their fellow counterparts. Until now researchers have not been unable to determine whether birds also use their eyes to communicate with members of the same species. This is the first study to have discovered eye-communication in birds.

"Jackdaw eyes are very unusual. Unlike their close relatives, the rooks and crows - which have very dark eyes - jackdaw eyes are almost white and their striking pale irises are very conspicuous against their dark feathers," Gabrielle Davidson of the University of Cambridge and lead author of the study said in a statement.

Most birds in the avian world have either black or dark brown eyes, but about 10 percent of the perching birds possess bright eyes.

Researchers conducted a study to determine whether jackdaws use their bright eyes to keep off their counterparts from coming near to their nests. For the study, the researchers placed four different pictures of jackdaws in 100 nest boxes. The pictures were either a pair of jackdaw eyes; pair of jackdaw eyes and face, jackdaw's face with a pair of rook's eyes or black (the control).

The researchers then observed the jackdaw's reaction while they noticed the eyes in the nest. They found that jackdaws were least likely to approach the nests that had the picture of jackdaws and eyes when compared to other nests. These perched birds were also more likely to spend less time around such nests.

"Jackdaws are unique among the crow family in that they nest in cavities in trees. These hollows are natural - the birds cannot excavate their own nest cavities as some woodpeckers do - so they have to compete for a limited resource. And because jackdaws nest in close proximity to each other, they fight a lot to gain the best nesting sites," Davidson said.

The finding is published in the journal Biology Letters.

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