By Ella Davies
Reporter, BBC Nature
Jackdaws' conspicuous bright eyes frighten off their competitors, according to scientists.
Researchers from the University of Cambridge, UK, tested whether the dark birds' striking blue-white eyes help them to protect nest sites.
They found that jackdaws avoided nest boxes when they could see the eyes of a jackdaw inside.
Experts suggest this is the first evidence that bright eyes could act as signals in the bird world.
The results were published in the Royal Society journal Biology Letters.
Jackdaws are members of the corvid family, which includes birds such as crows, ravens and jays, and are known for their intelligence.