The ultimate goal for any animal (except humans!) is to successfully pass on their genes to their offspring. For females of any species, this means picking the strongest, healthiest male to breed with. For robins, their red breast makes them highly visible to predators such as sparrowhawks. For a male to survive to maturity, it has to be strong enough to fly away and hide. Therefore, he will probably pass on strong genes to any offspring. A bright red breast is also a sign of general healthiness and lack of parasites - if an individual is injured, hungry, or over-run by parasites, it will have very dull plumage, and therefore will not be attractive to females.
Evolution is based on survival of the fittest, and a nice bright chest lets the females know that the male will pass on good genes to her offspring!
Evolution is based on survival of the fittest, and a nice bright chest lets the females know that the male will pass on good genes to her offspring!
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Birds have excellent color vision, and they use color signals to communicate. For example, sea gulls often have a red dot on their bill. The dot signals the chick to peck at the adult's bill and that peck stimulates the adult to regurgitate food to feed the chicks. Experiments have shown that the chicks will not peck at dots of a different color, only red dots.
Birds also use different plumages to identify each other to other birds. Closely related species often have different plumages, in addition to different songs, or mating calls. This is important because it is usually a bad idea to mate with individuals of a different species, since each species has a specific niche, or way of living, and their morphology is well adapted to that sort of niche. For example, sparrows have strong bills that crush seeds, but hummingbirds have long and slender bills to drink nectar. If 2 birds with different niches mate, their offsprings (even if they are not sterile) may have traits intermediate to both species. The hybrid between, say, a nut cracker and a nectar eater may have a bill that is not strong enough to crack nuts but at the same time not long or slender enough to drink nectar. Such a hybrid may starve and never grow old enough to reproduce. Therefore it is very important for birds to mate only with individuals of the same species. To help them do that, each species has evolved a different plumage and/or mating call or dances to minimize interspecific hybridization. The European robin has evolved a red breast and they also sing a unique song, in order to identify each other as the same species.
Birds also use different plumages to identify each other to other birds. Closely related species often have different plumages, in addition to different songs, or mating calls. This is important because it is usually a bad idea to mate with individuals of a different species, since each species has a specific niche, or way of living, and their morphology is well adapted to that sort of niche. For example, sparrows have strong bills that crush seeds, but hummingbirds have long and slender bills to drink nectar. If 2 birds with different niches mate, their offsprings (even if they are not sterile) may have traits intermediate to both species. The hybrid between, say, a nut cracker and a nectar eater may have a bill that is not strong enough to crack nuts but at the same time not long or slender enough to drink nectar. Such a hybrid may starve and never grow old enough to reproduce. Therefore it is very important for birds to mate only with individuals of the same species. To help them do that, each species has evolved a different plumage and/or mating call or dances to minimize interspecific hybridization. The European robin has evolved a red breast and they also sing a unique song, in order to identify each other as the same species.
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its obv a territorial marker (m/f robins have ID plumage)..a signal to other male robins to stay out or risk a fatal fight
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Probably identification to each other and for sexual selection (the redder the healthier).