Barn owl nestlings recognise their siblings' calls, according to researchers.
Instead of competing aggressively for food, young barn owls are known to negotiate by calling out.
A team of scientists in Switzerland discovered that the owlets have remarkably individual calls.
They suggest this is to communicate each birds' needs and identity in the nest.
The findings were announced in the Journal of Evolutionary Biologyby Dr Amelie Dreiss and colleagues at the University of Lausanne, Switzerland.