Sex Rhythm in the Ruffed Grouse (Bonasa Umbellus Linn.) and Other Birds

Abstract

Plates VHI-XI. THE sex instinct is generally conceded to be the most powerful of all agencies controlling the actions of birds. It may seem heretical , therefore, to begin this paper with the statement that, after fifteen years of rather intensive study of the Ruffed Grouse, 2 I am convinced that this species, and perhaps all species of birds, are not cognizant of sex as such, even during the breeding season, and that sex reactions are based primarily upon differences in size or vigor of individuals irrespective of sex. My observations on Grouse are based primarily upon birds reared in captivity, because these birds, being devoid of fear of man, react toward one another before one's eyes in a perfectly normal manner, and one is able to repeat and check his observations dozens of times for every single observation made on wild birds. Some of the observations have been made in large woodland enclosures , others in small pens, and, during the past three years, largely in pens with wire floors where, incidentally, the birds seem to behave exactly like others in the woods. In 1931 I reared 57 birds, in 1932, 77, and in 1933, 50, so that I have had plenty of captive birds to watch, and they have behaved quite uniformly according to the pattern which I shall attempt to describe.