Contribution à l'étude de la ptérylose chez Perisoreus canadensis (Linnaeus), (Aves : Corvidae)
The pterylosis of the Corvidae is generally not well known. The purpose of the present study is to describe the pterylography of the gray jay (Perisoreus canadensis). A French terminology is proposed for the various elements of the feather tracts and for the apteria. Down is present on the apteria of the winter individuals examined. The circles of feathers around the eyes are considered as feather tracts rather than elements of the other head feather tracts. There is no median fissure in the dorsal saddle, and the posterior element of the dorsal feather tract is attached to the saddle by a narrow band of feathers. There are 20 remiges; the 10th secondary is reduced in size and difficult to identify on study skins. The arrangement, shape, and orientation of the wing coverts are discussed. There are 12 rectrices, 6 on each side, but there are only 10 upper-tail coverts; a pair of filoplumes corresponds to each of them. Twelve (12) greater under tail coverts were found. A description of the natal down is provided. Individual variation in the pterylosis of the gray jay is slight, and there appears to be no sexual dimorphism; similarly, the bilateral symmetry is very high, perhaps perfect. Finally, it is suggested that the presence of down on the apteria in winter may be an adaptation to the low winter temperatures in the range of the species, and to breeding early in cold climate.