Distant Drumming: morphological correlates of habitat and courtship behaviour in the Ruffed Grouse (Bonasa umbellus)

Abstract

The Ruffed Grouse (Bonasa umbellus) is a resident game bird of North America. Unlike other birds, male Ruffed Grouse do not vocalize during courtship, and are dependent upon ‘drumming’, a ‘wingbeat’ display, for the acoustic component of their courtship behaviour. Because this wingbeat display is unique, I investigated morphological correlates that could underlie its production. First, I examined wing shape among grouse from museum specimens using various morphometrics. I found that wing morphology corresponds with habitat, behaviour and phylogentic relationships within Tetraoninae. Next, I examined the brains of male and female Ruffed Grouse. I detected seasonal plasticity between males collected during the breeding and non-breeding seasons; those collected during the breeding season had larger motor regions than those collected during the non-breeding season. My findings indicate that habitat and wing shape are correlated among grouse, and that seasonal changes in brain morphology contribute to the production of the drumming display.