Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences

First Advisor

Daniel Mennill


Psychology, Biological sciences, Animal communication, Frequency matching, Gargle call, Overlapping, Signal reliability, Song rate




The traditional view of birdsong indicates that it functions in territory defence and mate attraction. Recent literature focuses on aggressive signalling between males during territorial song contests. Using a protocol that simulates territorial intruders with song playback and a taxidermic model, four previous studies showed that quiet song predicts attack in several species. Using this protocol, I examined aggressive signals in black-capped chickadees, Poecile atricapillus . I explored which signals predict attack on a taxidermic mount, a potential graded signalling system, and how individual rank affects aggressive signalling. I found song rate and gargle calling predict attack in chickadees. Also, song rate and gargle calling may constitute a graded signalling system used to communicate increasing levels of threat. Finally, I found no effect of male rank on aggressive signalling strategies. This thesis provides new insight into avian aggressive signalling and new avenues for research on graded signalling.