ESTABLISHING BODY-SIZE INDICATORS IN A STUDY OF FEMALE SPRUCE GROUSE DENDRAGAPUS-CANADENSIS

Seven measurements were taken from 72 adult and yearling spruce grouse Dendragapus canadensis hens collected over a 10-year period from nort h-eastern Ontario, Canada. A principal components analysis (PCA) indic ated keel ridge length, keel total length, and femur length, these bei ng the most representative measurement of general body size. Skeletal mass, caecal length, wing length, and foot length had lower character loadings on the first principal component axis (PC1), suggesting they are unreliable measurements of body size. Measurements taken from bone s (i.e. keel, femur) were more representative of general body size tha n external morphometric measurements (e.g. wing and foot length) which ornithologists traditionally use to estimate body size. Pre-laying ad ults were the smallest individuals and pre-laying yearlings the larges t in the population studied. A discriminant functions analysis (DFA) o f the seven measurements, with separated body mass as an eighth variab le, demonstrated distinct separation between pre-laying and post-layin g groups of birds on the basis of separated body mass. Keel ridge leng th was further implicated as an effective variable in the discriminati on of birds from different laying groups.