Behaviour of captive spruce grouse at the time broods break up and juveniles disperse

Abstract

Behaviour of captive spruce grouse (Canachites canadensis franklinii) was observed at the time broods break up at the end of summer and during the period when juveniles disperse in autumn and the following spring. We saw no overt aggression among members of broods at the time of brood break-up nor among unrelated grouse at the onset of autumn dispersal. By contrast, aggressive interactions were common among members of each sex at the onset of spring dispersal. We suggest that broods of spruce grouse break up when the level of mutual attraction among them wanes to a point where individuals no longer respond to the brood calls and begin to move independently of one another. Autumn dispersal appears to be an intrinsically determined phenomenon, not requiring any overt aggressive stimuli from conspecifics, whereas spring dispersal appears to be environmentally determined, requiring aggressive interactions with more dominant individuals.