Foraging at patches: interactions between common and roseate terns

In foraging groups in the Long Island Sound area of the eastern United States, Roseate Terns Sterna dougalli plunged for longer periods and from greater heights than did Common Terns Sterna hirundo. Roseate Terns were rarer than expected in dense feeding groups where they tended to occur at the peripheries but they were more common than expected in more dispersed groups. Roseates were also more successful per plunge than were Common Terns in dispersed groups. The species appeared to partition food on the basis of patchiness: Common Terns were more successful in large groups over presumably larger patches of prey while Roseate Terns had more success in smaller groups feeding on more dispersed prey.