Why do some birds display bright colors?

The story behind the answer

Mate attraction: In many birds, vivid plumage is shaped by sexual selection. Bright colors act as “honest signals” of quality because they are costly to produce and maintain. Reds and yellows often come from carotenoids obtained in the diet, so richer color can indicate strong foraging ability, robust immune function, and low parasite load. Females (or sometimes males) prefer these signals, driving the spectacular displays of peacocks, birds-of-paradise, and male cardinals, especially during breeding season.

Remember: “Bright means ‘right’ for a mate.” The other choices are less typical—aposematic warning is rare in birds, camouflage tends to favor duller tones, and while feathers can affect heat, vivid coloration primarily evolved to win mates, not to regulate temperature.