Abstract and Summary
Observations of the behavior of newly-fledged bank swallows suggest that sibling recognition may be a mechanism promoting location of the home burrow in their large, dense colonies and of cohesion of family groups following departure from the burrow. We tested for sibling recognition in the field by comparing the antiphonal response of sibling groups to the recorded calls of own vs. unrelated sibling groups. Birds responded more to the calls of their own groups. In a laboratory experiment we raised chicks in isolation from 8–10 to 20 days of age and exposed them to a call of an unrelated chick. When tested in a choice situation at 15–20 days, chicks approached the familiar call in preference to a different call which they had not previously heard. We suggest that sibling recognition is based on familiarity, i.e., that it requires a period in which the calls of siblings are learned.