The colorful phenotypes of birds have long provided rich source material for evolutionary
biologists. Avian plumage, beaks, skin, and eggs—which exhibit a stunning range of cryptic …

Classical sexual selection theory,,, provides a well-supported conceptual framework for
understanding the evolution and signalling function of male ornaments. It predicts that males …

Carotenoid-based polymorphisms are widespread in populations of birds, fish, and reptiles,
1 but generally little is known about the factors affecting their maintenance in populations. 2 …

Some birds undergo seasonal colour change by moulting twice each year, typically
alternating between a cryptic, non‐breeding plumage and a conspicuous, breeding …

Avian plumage has captivated scientists and the public alike for generations and has been a
fundamental study system for research into signal evolution. By contrast, relatively little …

Highlights•We review hypotheses for honest signalling and physiological/social cost
models.•We review key empirical studies to determine support for these hypotheses.•Social …

Female ornaments have long been considered non-functional, but a paradigm shift has
occurred over the 2 last decades. The adaptive nature of female ornaments is now widely …

In many vertebrates, the enzymatic oxidation of dietary yellow carotenoids generates red
keto‐carotenoids giving color to ornaments. The oxidase CYP2J19 is here a key effector. Its …

Island environments have the potential to change evolutionary trajectories of morphological
traits in species relative to their mainland counterparts due to habitat and resource …

The visual morphologies in animals are associated positively or negatively with production,
adaptation, and behavioral characteristics. For rural farmers with limited records, these …