A Morphometrical Study of the Canada Goose, Branta canadensis interior Todd

Abstract

TlI• classification of Canada Geese of the genus Branta continues in a state of flux. Responsible in large measure for the lack of agreement among systematists is the dearth of an adequate series of specimens , both adults and downy young, from the breeding grounds. The need for adult specimens from the breeding range is, however, appreciably lessened when sufficient banding is done to show the breeding range of the various wintering populations from which collections are more easily obtained. This is particularly true in eastern North America where the breeding grounds of the various flyway populations are now fairly well understood. It is not true for the populations that migrate across the plains states. Because there has been insufficient banding to show the breeding grounds of these latter populations, a study based on wintering specimens from this area might be misleading. For example, any attempt to unravel the relationship of the various races by the use of specimens from the Gulf Coast would be especially deceiving, for individuals in flocks in that area range in size from that of Branta canadensis hutchinsii to Branta c. interior or B.c. mo.•tti (Arthur S. Hawkins, personal communication , 1945). In this study of variation in Branta c. interior, the usual handicap of lack of knowledge concerning the origins of the population examined is minimized since the breeding grounds are known with considerable exactness. Findings presented are based on data from a total of 414 geese trapped for banding purposes at Horseshoe Lake, Alexander County, Illinois, in the autumn of 1943. Sex and age of each bird were determined by criteria discussed by Elder (1946) and Hanson (1949a). The segment of the trapped population studied is believed to be, within each sex and age class, a random sample of the Horseshoe Lake flock, which in recent years has comprised about 50 per cent of the Mississippi flyway population. The breeding grounds of the Mississippi flyway population, which are discussed in detail by Hanson and Smith (1950), lie in the muskeg country of northern Ontario, inland from the west coast of James Bay and the south coast of Hudson Bay, between the Albany and Severn rivers. Geese termed "juveniles" in this report are birds from five to eight months of age; "adults" include all birds 17 or more months of age at time of study. As geese in their second year of life frequently ranked