Ever notice how some birds of the same species have colorful plumage while others have duller coloring? It is known as sexual dimorphism and is a common occurrence in the animal realm, including some species of birds. The male Ring-necked Pheasant2 has blue, green, and red colors on the head, occasionally a white-collar, and primarily red plumage, whereas the female pheasant is more of a solid brown. As another example, the gorgeous Eurasian Bullfinch1 male has an orange-pink abdomen while the female’s is light brown. As a result, during the breeding season, some male birds display vivid colors, while females fade in comparison to their gray or brown plumage.

Factors that Cause Sexual Dimorphism

1. Birds employ their plumage’s vivid colors to entice potential mates.

Then, one could question why there are such variances between the sexes of birds. The idea of sexual selection, established by Charles Darwin, the creator of the theory of evolution, may help to explain this.

In a word, sexual selection is one of the elements of natural selection. Contrary to the latter, however, sexual selection is more closely tied to a person’s capacity for procreation than to their likelihood of surviving. The development of physical traits (like plumage) as well as behavioral traits (like singing or understanding how to build nice nests) in males are among the factors that contribute to an animal’s ability to reproduce and, consequently, to guarantee its progeny. For females to agree to breed with males, these characteristics are essential.

The males of colorful birds can then more effectively “seduce” their spouse and “crowd out” their competitors. The most well-known example is the peacock, which flaunts its spectacular tail with glistening colors to both dazzle and entice females. Males strut, and females make their decisions.

Darwin claimed that women look for traits in their partners that demonstrate his strength and ability to survive in his environment. Therefore, their kids will have a better chance of surviving if they mate with the correct guy.

2. The color paradox: Bright hues make birds more vulnerable to predators.

There is a drawback to flashy coloration: it puts the male at risk of being eaten by predators and threatens his survival, which is contrary to Darwin’s idea of natural selection. In fact, why choose those that are most obvious to predators if females seek out the guy with the finest genetic makeup to ensure their progeny have the highest chance of survival?

In other words, how do we account for the evolution of striking sexual characteristics (bright colors) that appear to defy natural selection?

The bright color of male feathers would be seen by females as a sign of strength and good health, according to the handicap principle, which was proposed in the 1970s by biologist Amotz Zahavi. Therefore, if these men are still alive despite these expensive and showy displays (which render colored males more vulnerable to predators), then this would indicate that they are the most energetic and, consequently, the best future parents.

Additional Factors

It’s important to bear in mind that birds observe one other and us in quite different ways. This is so because human vision differs from that of birds. For instance, while people are unable to see UV wavelengths, birds can. When compared to humans, they are also lot better at telling apart two colors that are similar. This is a contributing factor in the ability of many bird species to determine the gender of an individual despite the absence of sexual dimorphism to our eyes.


In summary, some male birds exhibit brilliant colors primarily to attract females, even though doing so increases their visibility to predators. Bright plumage colors can also be used to impress rivals and distinguish individuals between species. The fundamental causes of the sexual dimorphism of birds (with regard to colors) are thus explained by Darwin’s theory of sexual selection, but there is still much to learn about the courtship behaviors of birds.