Erithacus rubecula
Audio playback studies are often used to test the dear enemy effect in birds. These studies have demonstrated several bird species respond more aggressively to played back songs of strangers than to songs of neighbours; such species include the alder flycatcher ("Empidonax alnorum"), male blue grouse, European robin ("Erithacus rubecula"), and male banded wren ("Thryothorus pleurostictus").