Ornaments are equally informative in male and female birds

Ornaments are often less elaborate in females than males. Regardless of such sex differences, this meta-analysis across mutually-ornamented birds supports that ornamental traits could equally act as adaptive signals in males and females. Female ornaments are often reduced, male-like traits. Although these were long perceived as non-functional, it is now broadly accepted that female ornaments can be adaptive. However, it is unclear whether this is as common in females as it is in males, and whether ornaments fulfil similar signalling roles. Here, we apply a bivariate meta-analysis to a large dataset of ornaments in mutually ornamented birds. As expected, female ornament expression tends to be reduced compared to males. However, ornaments are equally strongly associated with indicators of condition and aspects of reproductive success in both sexes, regardless of the degree of sexual dimorphism. Thus, we show here in a paired comparison within-and-across species, that ornaments in birds provide similar information in both sexes: more ornamented individuals are in better condition and achieve higher reproductive success. Although limited by their correlational nature, these outcomes imply that female ornaments could widely function in a similar manner as male ornaments.

Automated summary

This article examines the ornament traits and adaptive signals in birds. The study finds that although female ornaments are often less elaborate than male ornaments, both sexes show similar associations between ornaments and indicators of health and reproductive success.