¹⁵N values may also be influenced by baseline variation in nitrogen sources, the observed patterns are consistent with trophic differences and highlight the role of diet in shaping plumage coloration. Our results highlight the importance of individual dietary strategies in shaping carotenoid-based color phenotypes through both direct (carotenoid acquisition) and indirect (nutritional condition) pathways, with distinct effects across different ornamental feather regions.
Silva et al. (2026) studied this question.