Analysis of records of 8665 Gray-crowned Rosy-Finches banded over 64 years in Montana, Wyoming, Colorado, and New Mexico revealed that the sexes tend to segregate latitudinally during winter. The sex ratios of Gray-crowned Rosy-Finches banded during winter in these four Rocky Mountain states varied linearly with latitude, males predominating toward the north (male:female ratio 2.2 in Montana), females toward the south (male:female ratio 0.6 in New Mexico).