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Why are male birds often more brightly colored than females?

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A zebra finch (Taeniopygia guttata) with a bright orange beak, gray head, orange cheek patch, and black-and-white striped tail perches on a branch. — Bird A brightly colored zebra finch (*Taeniopygia guttata*) perched on a branch.

In many bird species, males are more brightly colored than females due to sexual selection, an evolutionary process where specific traits provide a reproductive advantage.12

This phenomenon, known as sexual dimorphism, typically functions in two ways:

Intersexual Selection (Female Choice): Bright plumage serves as an indicator of a male's health and genetic quality. Females often choose mates based on these displays, which can also signal the quality of a male's territory and his ability to provide resources for offspring.2
Intrasexual Selection (Male Competition): Vivid colors can act as tools for intimidation, signaling dominance to other males when competing for territory or mates.2

While these bright colors increase a male's "sex appeal," they often come at a cost, as they can make the bird more visible to predators. Conversely, females are frequently cryptically colored, which provides essential camouflage, allowing them to remain concealed while nesting. In some species, such as the phalarope, these roles are reversed, and females exhibit the brighter plumage.12