Analysis shows sex ratios of gray-crowned rosy-finches vary with latitude in Montana and New Mexico, suggesting distinct wintering patterns.
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).
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Morrow et al. (2025) studied this question.
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