In birds, unlike reptiles, in the process of evolution. In birds, male and female beauty have a different nature. Why do male birds have a bright color
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 value 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 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.
On the other hand, in many birds, the females are also very brightly colored. The reasons for this are less obvious similar situation with women's songs, read the news, "Elements", 03/25/2015).
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 to new sign manifested only in males, this gene still has to come 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 likely 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. 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 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 plain-looking 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 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 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. It was previously noted that female birds practicing cooperative care of 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.
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 ...
To begin with, let's figure out why birds have color and why they need it.
Regarding this, there are many hypotheses that have not yet been fully proven by science, and therefore the question remains open. Difficulties and disputes arise from the fact that in some birds the color is extremely bright, multi-colored, while in others it is so nondescript at all that it is difficult to notice them.
Yet there are several general rules suitable for most birds. As, for example, the fact that birds with a bright color of feathers spend almost all their time in the upper reaches of trees, in the air or on the water. While birds with a duller color live on the ground.
In addition, the top plumage of birds is usually darker than the bottom.
Based on these facts, scientists concluded that the color of the birds is their protection. That is, plumage makes them as less visible to enemies as possible. Such protective coloring masks birds, adjusting to a certain habitat of a particular species of birds.
Now back to our original question. Why do females look more nondescript than males? Since the color of the plumage is a kind of protection, and females need it more, because she hatches eggs, by nature the females received this color to be more protected from enemies.
There is another reason for the bright color of males. Such colored plumage attracts the female during mating season. At this time, the plumage of males is the brightest.
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!
Questions with a choice of one correct answer.
A1. A sign of the fitness of birds for flight:
the appearance of a four-chambered heart,
horny shields on the legs,
the presence of hollow bones,
the presence of the coccygeal gland.
body temperature became unstable
formed a cover of horny substance,
four-chambered heart formed
reproduction began to occur with the help of eggs.
amount of food
day length,
air humidity,
air temperature.
consist of a trunk and a fan,
the air that is between them has a high thermal conductivity,
the air that is between them has a low thermal conductivity,
they are lubricated with an oily fluid that forms in the coccygeal gland.
the number of chicks in a brood,
the fact that their chicks are born sighted, pubescent, can run and find food on their own,
the laying of eggs extended in time, the chicks from which appear almost simultaneously,
Because their chicks hatch blind, almost naked, their parents must feed and protect them.
long caudal spine
lack of chest
keel on the sternum,
the presence of ribs in the abdominal spine.
appearance of the lungs
two circles of blood circulation,
constant body temperature
appearance of the cerebral cortex.
birds,
amphibians,
reptiles,
mammals.
chest bones,
clavicle,
edges of the first pair,
crow bones.
cervical spine,
sacral spine,
chest,
lanterns.
the presence of two circles of blood circulation,
complete separation of arterial and venous blood,
rhythmic work of the heart and automaticity,
the presence of valves between the atria and ventricles.
birds,
mammals,
flying fish,
reptiles.
attracts the attention of females of its own species,
repels females of another species,
makes them less noticeable against a bright background,
repels males of other species.
does not affect the volume and density of the body,
contributes to an increase in body volume and a decrease in its average density,
causes an increase in body volume and its average density,
leads to a decrease in the volume of the bird's body and an increase in its average density.
consume a lot of energy during the flight,
inhabited the ground-air habitat,
live in different natural areas,
eat plant and animal food.
Questions with the choice of several correct answers.
IN 1. What are the similarities between Archeopteryx and reptiles?
A) the body is covered with feathers,
b) has a long tail
C) the hind limbs have an elongated tarsus,
D) 4 toes on the feet (three pointing forward, one pointing back),
D) the jaws have teeth,
E) fingers with claws on the forelimbs.
Compliance tasks.
IN 2. Match Features circulatory system and classes of animals.
FEATURES CLASS
1. venous blood in the heart, A) Pisces,
2. there are four chambers in the heart, B) Birds.
3. two circles of blood circulation,
4. one circle of blood circulation,
5. venous blood from the heart goes to the lungs,
6. there are two chambers in the heart.
Free answer task
(C1 - short, C2-C5 - full expanded).
C1. Find errors in the given text. Indicate the numbers of sentences in which errors were made, explain them.
The features that distinguish birds from reptiles include the progressive development of the organs of vision, hearing, and coordination of movements.
In birds, thermoregulation is somewhat worse than in reptiles.
The four-chamber heart of birds has an incomplete septum in the ventricle.
The adaptations of birds for flight include: a streamlined body shape, wings filled with a dense bone substance, the presence of gas exchange in both the lungs and air sacs.
C3. In some forest biocenoses, to protect chicken birds, mass shooting of daytime birds was carried out. birds of prey. Explain how this event affected the number of chickens.
C4. Name the type of protective coloration from enemies in females of open nesting birds. Explain its meaning and relative nature.
C5. AT middle lane insectivorous birds arrive much later than herbivorous ones. How can this be explained?
C6. What adaptations for flight arise in the structure of the skeleton of birds?
Answers to the tasks of part A
| № | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| answer | 3 | 3 | 2 | 2 | 4 | 3 | 3 | 1 |
| № | 9 | 10 | 11 | 12 | 13 | 14 | 15 | |
| answer | 2 | 4 | 2 | 1 | 1 | 2 | 1 |
Answers to the tasks of part B
| job number | 1 | 2 |
| answer | BDE | ABBABA |
Answers to the tasks of part C
C2. Response elements:
molting, development of a dense feather cover;
fat storage,
storage and change of feed;
travel and flights.
at first, the number of chickens increased, since their enemies (naturally regulating the number) were destroyed;
then the number of chickens decreased due to lack of food;
the number of sick and weakened individuals increased due to the spread of diseases and the absence of predators, as a result of which their numbers decreased.