November 25, 2014
Real Life Angry Bird
Aggression rates throughout the year between Evening Grosbeaks are low; few attacks are reciprocated. As we have previously mentioned during winter, males are dominant over females. This is possibly reinforced by plumage cues, especially characteristics of the head and possibly wings. Threat displays include the Crown Fluff (erection of the feathers on crown of head, often as prelude to another aggressive behavior), Vocal Displacement (displacement following single note call), Open-bill Threat (one bird orients toward another and opens bill, displacing second bird without contact), Repeated Bill Threat (series of Open-bill Threats, sometimes followed by physical contact). This particular individual in the clip appears to display all of these interactions along with a body posture that has actually been associated with courtship and nest building in scientific literature; wings are held close to the body and lowered while the tail is cocked upwards.