How tree sparrows recognize foreign eggs in their nests

Many birds have reason to worry that the eggs in their nest might not be their own: birds often deposit eggs into other nests and it is not easy for parents to tell their eggs from others. Researchers at the University of Veterinary Medicine, Vienna have discovered that tree sparrows can recognise eggs deposited by other tree sparrows but do not always reject them. The results are published in the online journal Plos One.