A test of the effect of testosterone on a sexually selected carotenoid trait in a cardueline finch

Abstract

A great number of secondary sexual traits are assumed to have evolved as honest signals of individual quality. It is known that androgens regulate many male secondary traits as well as reproductive behavior. The expression of melanin‐based coloration is modulated by androgens, particularly testosterone, and there is some evidence that carotenoid‐based coloration may also be under androgen control. In the European serin, Serinus serinus, male carotenoid‐based plumage coloration is a sexually selected trait, subjected to female choice. In this experiment, we investigated if testosterone influences the expression of this trait by manipulating testosterone levels during molt and assessing how it affected plumage color expression after molt. We found that testosterone had only a negative effect on the size of the yellow ornament. Our experiment shows that testosterone had a limited effect on carotenoid‐based coloration of a cardueline finch.

Oestradiol reduces female bill colour in a mutually ornamented bird

“…The size of the oestradiolcontaining silastic implant was based on previous studies with other passerine birds of similar size (e.g. [48,49]), especially those on zebra finch (e.g. [50][51][52][53]) (another estrildid), after adjusting for the difference in body mass.…”