Take, for example, to compare the peacock female and male. The female looks very much like a chicken - an unsightly grayish bird. However, on the other hand, how good the male is - the brightest bright plumage.
Male birds are always more beautiful in their plumage than females, why did nature order it this way?
In nature, everything is thought out to the smallest detail and it is not in vain that male birds have such bright colors. Firstly, with their catchy plumage, males lure females for mating, and secondly, with the same plumage, they scare away other males (in other words, their own probable competitors).
Why do females have such pale plumage?
Since the females incubate from the laid eggs of the chicks. And sitting in the nest on her own laid eggs, the female should be very invisible to possible predators. Females incubating eggs actually connect with tree branches and do not dazzle with plumage.
So nature thought out everything to the smallest detail (to the feather). The unsightly female herself chooses a male for mating for herself, she looks at the plumage and the courage and strength of the male.
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Take, for example, to compare the peacock female and male. The female looks very much like a chicken - an unsightly grayish bird. However, on the other hand, how good the male is - the brightest bright plumage. Male birds are always more beautiful in their plumage than females, why did nature order it this way? In nature, everything is thought out to the smallest detail and it is not in vain that male birds have such bright colors ...
Many birds wear colorful outfits. Feathers colored in different ways form the most fantastic patterns, the colors of which shimmer, shine or cast in many shades.
Several coloring substances create such optical effects and internal structure(micro structure) pen. The cornea dyes belong to two groups of compounds. Give feathers all sorts of shades of brown melanin - black or brown pigments, and from yellow to deep red - carotenoids. Melanins are produced by the body itself, and birds get carotenoids from food. Therefore, the color of plumage depends on nutrition. Melanins and carotenoids can combine in the most incredible combinations. In many of our songbirds, yellow-green to olive colors are obtained by mixing yellow with brown or black.
However, the most striking effect is created not by dyes, but by the so-called structural paints. White sunlight, as you probably know from physics, is made up of light waves of all the colors of the rainbow. When some of these waves are absorbed or reflected from a surface, the eye perceives it as colored. If the countless tiny particles of the surface completely reflect the light, we see a flawless white color. In snow, for example, the role of mini-mirrors (mini-reflectors) is performed by ice crystals. At the feather, strongly dissected barbules and air-filled cells of the horny substance of barbules and shafts reflect and absorb light. The blue color is given by the porous keratin layer inside the barbs. If they contain carotenoids, a color palette from light yellow-green to deep purple appears. When light hits the feathers, they sparkle like blue, green, red, purple, golden yellow gems.
As soon as the bird turns around, its color will change or the gloss will disappear. Such a play of colors occurs on translucent thin layers of keratin, when light is reflected from both the upper and lower surfaces. Iridescent overflows on the head and neck of a drake or in gasoline films in puddles are of the same nature. The colorful plumage of birds helps them hide from enemies, find their relatives and attract individuals of the opposite sex.
Inhabitants of tropical rainforests tend to dress up in colorful clothes. Unfortunately, for many species of birds, their colorful plumage has done a disservice. In Cuba, for example, the tricolor macaw has disappeared. The Indians adorned themselves with flight and tail feathers and attached them to arrows. Females and males of parrots, petrels, loons, wrynecks, swifts have the same plumage. Not in many species, especially during the mating season, it differs: the outfit of males is much brighter than their girlfriends. The well-known red-chested bullfinches are males, and the modest brownish-gray ones are females.
It is not easy for enemies to detect a bittern painted in the tone of reeds and reeds: in case of danger, it stretches its neck vertically, lifts its head and, frozen in this position, becomes like a bunch of dry reed stalks. If you touch her, she won't move. Coloring gives strength to feathers. Most whites or very light birds, for example, in gulls, flight feathers or their ends are black. This edging wears out much less than the white areas.
Common dipper - Cinclus cinclus
Appearance. A dark brown bird the size of a starling with very dense, non-wetting plumage. The throat, chest, and in Asiatic birds also the abdomen are white; young gray with dark scaly pattern. Good pl...
Alpine jackdaw
userfiles/6p.graculus.mp3 ...
nesting affairs
Little birds build little nests. The nests of small hummingbirds are the size of a walnut shell, and are made of the most delicate material - moss, fluff, feathers, cobwebs. Some have...
In some species of birds, males are brighter than females, in others both sexes are brightly colored, and in others, both males and females are faded. An analysis of a large body of data on passerines has shed light on the reasons for this diversity. It turned out that the brightness of plumage in both sexes is positively correlated with body size, nesting in the tropics and the absence of long-distance migrations. Polygyny (male mating with many females) and lack of male care for offspring correlate with the brightness of males, but these factors contribute even more to the fading of females, which ultimately leads to strong sexual dimorphism in color. Cooperative care of offspring contributes to the development of bright plumage in females. The results obtained show that female beauty in birds is sometimes the result of a passive transfer to females of a trait that is useful only to males, but in many cases it also has its own adaptive significance associated with competition between females for social status and marriage partners.
According to the theory of sexual selection, the correlation between reproductive success and the number of sexual partners is usually stronger in males than in females (see links at the end of the news). Therefore, the male is “interested” in fertilizing as many females as possible, while the female, as a rule, has better things to do than chase after maximizing the number of partners. As a result, the female reproductive resource is in short supply, while the male one is in abundance. This gives rise to intense competition between males for females. Sexual selection, driven by this competition, leads to the development of adaptations that increase male attractiveness to females and menace to competitors. Often such traits are maintained by selection even if they reduce viability (see Handicap principle).
Therefore, it is not surprising that in many animals, including birds, males are brighter than females. Bright coloration (like the song) performs two important signaling functions: it informs females that they have a good potential partner in front of them, and males that they are in front of them. strong competitor with whom it is better not to mess with.
On the other hand, in many birds, the females are also very brightly colored. The reasons for this are less obvious (read about a similar situation with women's songs in the news, "Elements", 03/25/2015).
One of possible causes- passive transfer to females of a trait that is useful only to males. The fact is that the genetic determination of a sexually dimorphic trait is generally more complicated than that of a monomorphic one. For example, in order for the color to become brighter in both sexes, some mutation in one of the genes that affects color may be enough. But in order for a new trait to appear only in males, this gene must also fall under the control of a genetic switch (see cis-regulatory elements), controlled, say, by testosterone. This makes the evolution of sexual dimorphism difficult. In other words, selection acting on one of the sexes imposes certain restrictions on the possibilities of evolution of the other sex. The selection of males according to the brightness of color can automatically "pull" the brightness of the female plumage along with it.
But this difficulty, of course, is surmountable, since we see in nature so many cases of sexual dimorphism in color. In addition, a bright female outfit can have its own adaptive value. After all, females of many species also compete with each other for certain resources - from food and territory to social status and caring males. In this case, it may also be useful for them to demonstrate their unsurpassed advantages to rivals and gentlemen with the help of bright plumage.
To understand the reasons for the amazing variety of bird outfits, biologists from New Zealand, Australia and Germany analyzed data on all 5983 species of passerine birds (the passerine order includes 61% of the species diversity modern birds) depicted in the monumental Handbook of the Birds of the World.
The authors developed a universal method for quantifying the brightness of coloration, which makes it possible to compare dissimilar species (Fig. 2). As shown in Figure 2, what was actually assessed was not brightness or flashiness, but the “masculinity” of coloration, that is, how much this or that color scheme is characteristic for males, but not for female passerines. When the authors later checked which colors turned out to be “masculine” and which were “feminine”, it turned out that everything converges: bright, catchy colors fell into the first group, and the second is mainly represented by a modest yellowish-brown range.
Thus, for males and females of each species, one number was obtained that characterizes the flashiness of coloration. To find out what determines the brightness of the plumage of females and males, these numbers were compared with each other and with the parameters of lifestyle, behavior, family and social organization birds.
Some of the obtained results are shown in fig. 3. Sophisticated statistical analysis, during which the structure of the phylogenetic tree was taken into account and corrections for kinship were made, made it possible to reconstruct the most probable causal relationships (Fig. 4).
1. There is a positive correlation between the brightness of male and female coloration, which cannot be completely attributed to a similar effect of selection on both sexes. This means that the evolutionary-genetic constraints discussed above, which lead to the passive transfer of traits useful to one sex (usually males) to the other (usually females), play a significant role in the evolution of passerine coloration. This is illustrated by the thickest black arrow in Fig. 4.
2. There is a clear relationship between color intensity and body size. In larger species, both sexes are colored brighter on average. This can be explained by the fact that in passerines, an increase in body size reduces the chances of a predator getting for dinner. Predatory selection favors the development of camouflage coloration, while sexual (or, in a broader term, social) selection works in the opposite direction, increasing the brightness of the plumage. At small birds outweighs the first trend, in large - the second.
3. Strong asymmetric sexual selection, which acts mainly on males (which is typical for polygynous species without paternal care for offspring and with sharp dimorphism in size), contributes not only (and even not so much) to an increase in the brightness of the male attire, but to a decrease in the brightness of the female. As a result, sexual dimorphism in color reaches a maximum (Fig. 3d shows that in species with bright males and dull females, sexual selection is most intense). Why asymmetric sexual selection makes males bright is understandable. But why do females become pale at the same time? There are two explanations that are not mutually exclusive. Firstly, in such a situation, females, as a rule, simply do not need to be bright. Polygyny and purely female concern for offspring make females such a “scarce commodity” that the task of attracting marriage partners ceases to exist for them: even the most gray and nondescript one will still have an excess of suitors. Competition between females for food and other resources in such species is also, as a rule, weakly expressed. Secondly, in this situation, the "evolutionary interests" of the two sexes (that is, the direction of selection acting on males and females) are so different that selection must support the formation of genetic switches that allow traits that are useful only for males not to appear in the female phenotype. . Thus, asymmetric sexual selection contributes to breaking the relationship between male and female coloration, which was discussed above in paragraph 1.
4. In species that breed in the tropics and do not make distant migrations, both males and females are often brightly colored. Perhaps this is due to the fact that tropical birds (and many other tropical animals) are characterized by more intense intraspecific competition. As a result, among tropical species the percentage of K-strategists is higher (see r / K-selection theory): many of them have small clutches, both parents take part in caring for offspring, and the relationship between spouses is long and cordial. In conditions of heightened competition, bright coloration can perform useful signaling functions in both sexes.
5. Some birds form communities in which the chicks are cared for by more than their biological parents (cooperative breeding). In such communities, the reproductive success of both sexes strongly depends on the social status and the ability to raise and maintain it, including with the help of various signals. Previously, it was noted that female birds practicing cooperative care for offspring sometimes even sing more actively than males (see: Female red-tailed buntings sing more actively and more diversely than males, "Elements", 03/25/2015). Now we can add to this that they are not inclined to yield to males in terms of the brightness of their plumage. The most plausible explanation for this, again, is increased competition between females for social status, male attention, and other enduring values.
Thus, the study did much to elucidate the evolutionary mechanisms behind the amazing variety of male and female bird outfits. Characteristically, all the discovered facts fit perfectly into the theory of sexual selection and other classical evolutionary models.
Why are male birds brighter than female birds?
In order to understand why this happens, we must first understand why birds need color at all?
Many explanations have been given about this, but science has not yet fully resolved this issue. The reason for the difficulty is that some birds have unusual, multi-colored plumage, while others do not. Some are like bright banners, while others are hard to notice.
All we can do is try to find a few rules that are true for most birds. One of them is that birds with bright plumage spend most of their time in the tops of trees, in the air or on the water. Nondescript birds live on or near the ground.
Another rule, but with many exceptions, is that the upper parts of the birds are darker than the lower parts.
These facts led science to suggest that the color of the plumage plays a protective role so that the birds are as inconspicuous as possible to their enemies. This is called "protective coloration". The color of the snipe perfectly camouflages them in the grass of the swamps where they live. The coloring of woodcocks is very similar to fallen leaves.
But since colors protect birds, who needs it more - a male or a female? Of course, the female, since she incubates eggs in the nest. Therefore, nature gave it a more nondescript color in order to better protect it from enemies.
Another reason for the bright plumage in males is that it helps to attract a female during the mating season. Then the color of the males becomes the brightest. Even birds, as you can see, love at first sight!
In some species of birds, males are brighter than females, in others both sexes are brightly colored, and in others, both males and females are faded. An analysis of a large body of data on passerines has shed light on the reasons for this diversity. It turned out that the brightness of plumage in both sexes is positively correlated with body size, nesting in the tropics and the absence of long-distance migrations. Polygyny (male mating with many females) and lack of male care for offspring correlate with the brightness of males, but these factors contribute even more to the fading of females, which ultimately leads to strong sexual dimorphism in color. Cooperative care of offspring contributes to the development of bright plumage in females. The results obtained show that female beauty in birds is sometimes the result of a passive transfer to females of a trait that is useful only to males, but in many cases it also has its own adaptive significance associated with competition between females for social status and marriage partners.
According to the theory of sexual selection, the correlation between reproductive success and the number of sexual partners is usually stronger in males than in females (see links at the end of the news). Therefore, the male is “interested” in fertilizing as many females as possible, while the female, as a rule, has better things to do than chase after maximizing the number of partners. As a result, the female reproductive resource is in short supply, while the male one is in abundance. This gives rise to intense competition between males for females. Sexual selection, driven by this competition, leads to the development of adaptations that increase male attractiveness to females and menace to competitors. Often such traits are maintained by selection even if they reduce viability (see Handicap principle).
Therefore, it is not surprising that in many animals, including birds, males are brighter than females. Bright coloring (like the song) performs two important signal functions: it informs females that they have a good potential partner in front of them, and males that they have a strong competitor in front of them, with whom it is better not to mess with.
One of the possible reasons is the passive transfer to females of a trait that is useful only to males. The fact is that the genetic determination of a sexually dimorphic trait is generally more complicated than that of a monomorphic one. For example, in order for the color to become brighter in both sexes, some mutation in one of the genes that affects color may be enough. But in order for a new trait to appear only in males, this gene must also fall under the control of a genetic switch (see cis-regulatory elements), controlled, say, by testosterone. This makes the evolution of sexual dimorphism difficult. In other words, selection acting on one of the sexes imposes certain restrictions on the possibilities of evolution of the other sex. The selection of males according to the brightness of color can automatically "pull" the brightness of the female plumage along with it.
But this difficulty, of course, is surmountable, since we see in nature so many cases of sexual dimorphism in color. In addition, a bright female outfit can have its own adaptive value. After all, females of many species also compete with each other for certain resources - from food and territory to social status and caring males. In this case, it may also be useful for them to demonstrate their unsurpassed advantages to rivals and gentlemen with the help of bright plumage.
To understand the reasons for the amazing variety of bird outfits, biologists from New Zealand, Australia and Germany analyzed data on all 5983 species of passerine birds (the passerine order includes 61% of the species diversity of modern birds) depicted in the monumental Handbook of the Birds of the World.
The authors developed a universal method for quantifying the brightness of coloration, which makes it possible to compare dissimilar species (Fig. 2). As shown in Figure 2, what was actually assessed was not brightness or flashiness, but the “masculinity” of coloration, that is, how much this or that color scheme is characteristic for males, but not for female passerines. When the authors later checked which colors turned out to be “masculine” and which were “feminine”, it turned out that everything converges: bright, catchy colors fell into the first group, and the second is mainly represented by a modest yellowish-brown range.
Thus, for males and females of each species, one number was obtained that characterizes the flashiness of coloration. To find out what determines the brightness of the plumage of females and males, these numbers were compared with each other and with the parameters of the lifestyle, behavior, family and social organization of birds.
Some of the obtained results are shown in fig. 3. Sophisticated statistical analysis, during which the structure of the phylogenetic tree was taken into account and corrections for kinship were made, made it possible to reconstruct the most probable causal relationships (Fig. 4).
1. There is a positive correlation between the brightness of male and female coloration, which cannot be completely attributed to a similar effect of selection on both sexes. This means that the evolutionary-genetic constraints discussed above, which lead to the passive transfer of traits useful to one sex (usually males) to the other (usually females), play a significant role in the evolution of passerine coloration. This is illustrated by the thickest black arrow in Fig. 4.
2. There is a clear relationship between color brightness and body size. In larger species, both sexes are colored brighter on average. This can be explained by the fact that in passerines, an increase in body size reduces the chances of a predator getting for dinner. Predatory selection favors the development of camouflage coloration, while sexual (or, in a broader term, social) selection works in the opposite direction, increasing the brightness of the plumage. In small birds, the first tendency outweighs, in large birds, the second.
3. Strong asymmetric sexual selection, acting mainly on males (which is typical for polygynous species without paternal care for offspring and with a sharp dimorphism in size), contributes not only (and even not so much) to an increase in the brightness of the male attire, but to a decrease in the brightness of the female. As a result, sexual dimorphism in color reaches a maximum (Fig. 3d shows that in species with bright males and dull females, sexual selection is most intense). Why asymmetric sexual selection makes males bright is understandable. But why do females become faded at the same time? There are two explanations that are not mutually exclusive. Firstly, in such a situation, females, as a rule, simply do not need to be bright. Polygyny and purely female concern for offspring make females such a “scarce commodity” that the task of attracting marriage partners ceases to exist for them: even the most gray and unprepossessing will still have an excess of suitors. Competition between females for food and other resources in such species is also, as a rule, weakly expressed. Secondly, in this situation, the "evolutionary interests" of the two sexes (that is, the direction of selection acting on males and females) are so different that selection must support the formation of genetic switches that allow traits that are useful only for males not to appear in the female phenotype. . Thus, asymmetric sexual selection contributes to breaking the relationship between male and female coloration, which was discussed above in paragraph 1.
4. In species that breed in the tropics and do not make distant migrations, both males and females are often brightly colored. Perhaps this is due to the fact that tropical birds (and many other tropical animals) are characterized by more intense intraspecific competition. As a result, among tropical species, the percentage of K-strategists is higher (see r / K-selection theory): many of them have small clutches, both parents take part in caring for offspring, and relations between spouses are long and cordial. In conditions of heightened competition, bright coloration can perform useful signaling functions in both sexes.
5. Some birds form communities in which the chicks are cared for not only by their biological parents (joint care of offspring, Cooperative breeding). In such communities, the reproductive success of both sexes strongly depends on the social status and the ability to raise and maintain it, including with the help of various signals. It has previously been observed that female birds practicing cooperative care of their offspring sometimes even sing more actively than males. Now we can add to this that they are not inclined to yield to males in terms of the brightness of their plumage. The most plausible explanation for this, again, is increased competition between females for social status, male attention, and other enduring values.
Thus, the study did much to elucidate the evolutionary mechanisms behind the amazing variety of male and female bird outfits. Characteristically, all the discovered facts fit perfectly into the theory of sexual selection and other classical evolutionary models.
Source: James Dale, Cody J. Dey, Kaspar Delhey, Bart Kempenaers & Mihai Valcu. The effects of life history and sexual selection on male and female plumage coloration // Nature. Published online 04 November 2015.
Alexander Markov
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