A study of over 1,200 bird species reveals that female appearances are specifically evolved for 'social warfare' and predator evasion, rather than just being 'unfinished' versions of males.
April 1, 2026
Original Paper
Sex differences in avian plumage evolution: stronger effects of natural selection and social competition on females
EcoEvoRxiv · 10.32942/X22Q1V
The Takeaway
While male bird colors are usually attributed to sexual selection and attracting mates, this massive analysis shows that female plumage is shaped by entirely different, high-stakes pressures. It reveals that female birds evolve their look based on intense social competition for territory and the specific dangers of their nesting sites.
From the abstract
Sexual dichromatism in birds may evolve via sexual selection for increased elaboration in male plumage (Darwin hypothesis) or, alternatively, by natural selection for increased crypsis in female plumage (Wallace hypothesis). Both these effects may be counteracted by social competition promoting ornamentation in females. However, the relative roles of sexual, natural, and social selection in shaping patterns of plumage dichromatism have proved difficult to disentangle. To test these hypotheses in