Barn Swallows Distinguish Householders from Strangers

Incubating female Barn Swallows (*Hirundo rustica*) left their nests when an unfamiliar experimenter came closer than a resident of the house where the nest was located. In a field study in China, researchers measured the distance at which a bird took flight. The result suggests that the swallows distinguished a familiar householder from a stranger, but it does not establish exactly which cues the birds used to recognize a person.