Experimental evidence for sibling recognition in Common Terns (Sterna hirundo)

Young Common Terns (Sterna hirundo) did not respond preferentially to calls of siblings at 8 and 9 days of age, but did so by 12 days of age. In experiments with and without visual isolation, and with use of playback, we demonstrated a tendency to approach sibling begging calls. This differential response indicated sibling-recognition occurred, was based on experience, and involved vocal cues.