Niveles de corticosterona en las plumas y coloración basada en carotenoides en polls de ratoneo (Buteo buteo)

Abstract

[EN]: Animal communication signals can be defined as phenotypic traits produced by the signaler to obtain a benefit. Most of our understanding of the function and mechanisms that produce or maintain those signals are not restricted to adulthood. Instead, the display of such signals occurs during the nestling stage, which can play a function on parent-offspring conflicts or sibling competition. However, the mechanisms that may mediate the expression of those signals during growth are barely known. Here we explore the mediating effect of corticosterone levels on colouration of cere and legs, carotenoid-pigmented traits, in nestlings of buzzards (Buteo buteo). Corticosterone levels deposited in feathers can be a reliable and integrated index of stress response. Carotenoids can be diverted to physiological process or coloration and we hypothesized that corticosterone levels may mediate how carotenoids can be diverted to other functions than coloration. We found that carotenoid and corticosterone levels were positively associated, perhaps because as a result of higher metabolic activity in more stressed nestlings. However, carotenoid levels and colouration were not correlated. In addition, corticosterone, but not carotenoids, and coloration of cere and legs were negatively related in females but not in males. Altogether, our results support the idea that corticosterone plays a key role in influencing how a limited resource such as carotenoid pigments, is allocated and used by raptor nestlings for signaling or other needs. Our study showed a sex-specific mediating role of this stress hormone in raptor nestlings revealed by colouration of cere and legs. We encourage further studies exploring how nestlings cope with and respond to a wide range of stressors disentangling the relative effect of the three triangle composed by corticosterone, carotenoids and colouration under different environmental conditions during growth.