Olfaction in Snow Petrels

braska and Crook, Colorado, that had been collected by Sibley and Short (1964). The character index scores that we assigned were compared to those of Sibley and Short (unpubl. data) using two statistical tests. First, we correlated the plumage character scores that we assigned to each specimen with scores assigned to the same specimens by Sibley and Short. All 20 correlation coefficients (nine for plumage character values and one for the hybrid index value for each of two localities) were significant at the .Ol level. Second, we compared the values assigned in the two studies by means of an analysis of variance (Table 1). The upper part of the table deals with the variation in individual plumage character scores, whereas the lower part concerns the hybrid index scores. Within the upper part, we partition the variance due to (1) inherent differences among the characters and (2) differences in the way individual character scores were assigned in the two studies. In the lower part of the table, only that variance due to differences between the assignment of scores is partitioned. For both localities the variance associated with the characters is significant ( P < .OOl ). That is, the among-character