For a full-fledged cycle of life on our planet, the presence of birds of prey in nature is an obvious necessity.
Different types of birds have a natural gift to hunt large prey. Among them: hawks, representatives of eagle and falcon groups, gulls, owls and others. The unifying criteria for these species are:
- the role occupied in the natural chain;
- way of eating;
- lifestyle (time of day at which the bird starts hunting).
birds of prey
According to the systematization from the point of view of zoology, only falconiformes belong to the orders of diurnal birds of prey, these are the falcons themselves, hawks, eagles, buzzards, eagles, harriers.
It is noteworthy that indeed predator birds they have the same threatening and dangerous appearance: the beak is bent like a hook, and their claws are crooked and very sharp. The coloration of females and males is almost identical, but females are larger.
Rough-footed buzzard
Another name is zimnyak. This bird is considered the most famous predator among the forests of the tundra. She builds her nests throughout the Yamalo-Nenets autonomous region . The food of this predatory species is made up of mice - voles and lemming hamsters. It is characteristic that the numerical component of Rough-legged Buzzards directly depends on the sufficient population of the area with these rodents. Scientists - ornithologists argue that in the conditions of one area, buzzards may be present in excess, or not at all.
External signs rough-legged buzzard:
- Rough-legged Buzzard is a large bird;
- has wide wings (this visually makes it even larger);
- general color - light, slightly "red";
- on the belly and under the wings of a predator, black spots are localized, different in shape (they can form an individual plumage pattern).
Buzzards nest in woody areas, they line the nests with grass. If we are talking about the tundra, then in these areas the birds are usually located on the cliffs and hills. In the case of a fruitful year for mice, the nest of Rough-legged Rough-legged Buzzards can also be found on flat terrain, in swamps, in river lowlands.
Buzzards are migratory birds arriving from warm places in early spring. After the flight, they begin to twist their nests. Rough-legged buzzard egg size larger than chicken eggs, rounder in shape, they are spotted and have a White color. The richer the year for prey, the more eggs in the clutch of this bird of prey. The principle of natural selection plays a significant role in the survival of chicks, especially when there is not enough food, due to the poor harvest for rodents. Many chicks do not even have the opportunity to live up to the "flight" age, they are simply eaten by older and stronger chicks.
Buzzards zealously defend their nests. Attacks on people are unlikely, more often the birds simply scream loudly or rush at a person. But they fearlessly fight off arctic foxes or dogs, using strong claws. It happens that the Buzzard eats dead carcasses of deer and their entrails, or rotten fish.
With the arrival of the autumn period, and during it, these predators fly away to the regions of the middle lane.
bald eagle
It is one of the largest and largest birds of prey in Russia. His wingspan exceeds two meters, and the weight of the bird sometimes reaches seven kilograms. The owners of a pure white tail are predominantly adults, whose age is more than three years old, in the rest it is dark. Often a young sea eagle can be mistaken for a golden eagle. However, the tail of the golden eagle is slightly rounded, while that of the white-tailed tail has the shape of a sharp wedge.
White-tailed eagles nest almost all over the country, they avoid only extreme northern areas and dehydrated areas. They arrange their nests only in the crowns of trees, more often deciduous. Very rarely, the "eagle house" is located on steep cliffs.
Whitetails feed on fish and birds swimming in the water. This explains their desire to live near areas rich in water bodies. Their dwelling is located in the same place every year, has a very massive, layered structure up to a meter in height. In the open tundra expanses, the nest of the eagle is extremely rare to be found, more often it localized on hills or cliffs.
During early spring, the eagles already arrive from the south. The flight is carried out in pairs that are distinguished by constancy. Females lay from one to three eggs in the newly inhabited nest. The eggs are white with spots, similar in size to goose, but somewhat smaller. After the first egg is laid, female eagles begin incubation. The chicks emerge from the egg around the first half of June. Their growth is very rapid, plumage is fast.
In early August, the chicks fly out of the nest, however, they are under the supervision of their parents for a long time. Whitetails keep their way to the southern regions in early autumn.
White-tailed eagles feed on wild birds: geese, ducks, loons; also their diet consists of hares, large species of fish, rodents. Moreover, these birds of prey are lovers of carrion, or are hunting animals that are injured or sick and cannot resist.
White-tailed eagles are rare, valuable birds, they are listed in the Red Book of both our country and the international one. Often the eagle becomes a victim of hunters - poachers, which is very sad for nature and scientists.
Osprey
These birds of prey have a small number, are considered rare, and are listed on the pages of our Red Book.
Species signs:
- large size;
- contrasting color: white-yellow underbody; a dark stripe running across the bird's crop; from above, the body, tail and wings are dark in color; wide black stripes on the head;
- yellow eye color;
- in conditions of increased anxiety, these birds make peculiar sounds.
The habitat of these predators is the territory of the whole world, with the exception of the extreme northern regions. They winter in the African and South Asian tropics.
Ospreys choose, to ensure necessary conditions a habitat, areas with clear waters rich in fish. They nest in tall trees with dry tops, away from crowded places. Birds do not change their nests, returning to them every year. The clutch of the osprey contains up to four eggs at most, usually two or three. The eggs are dark in color, with purple spots of various localization.
Chicks live in the nest for about two months without leaving it. They become sexually mature when they reach the age of two.
The features of the hunting of these birds of prey are that, flying high above the water surface, they track down their main food - fish. Having noticed the victim, the osprey dives forward with its paws, and then takes off sharply, catching the victim. This bird is squeamish about carrion, so if hunger begins to exhaust, then a predator can hunt ducks or mice.
The osprey spends the winter between September and October.
The number of this species is inexorably declining, this is due to the direct extermination of predators, unfavorable ecology, and deforestation. All this makes it impossible for birds to nest safely.
Goshawk (hawk)
The bird is larger than a crow, weighing up to one and a half kilograms.
Character traits:
- distinct stripes running across the underside of the bird's body;
- dark gray upper body;
- very bright, yellow eyes;
- young goshawks are painted with red or brown tones.
Birds of this species have been persecuted for a very long time due to the fact that they were considered predators that bring special harm. As a result, their numbers have fallen, and now they are protected by law.
Hawks - goshawks feed on medium-sized fish and small animals such as rabbits, squirrels, and so on. They hunt dying animals that are doomed and weakened due to illness or injury. Due to this, predators are classified as forest orderlies.
Goshawk distribution zone - northern forest-tundra. They winter either where they nest or fly away to where it is warmer.
Harrier field
It is a bird that lives, more often, in open spaces - forest-tundra zones, forest-steppe and taiga strips. The main habitat condition is an abundance of small rodents.
The harrier is about the size of a crow, but with a longer tail and a graceful body. The colors of the male and female are different.
Features of the color of the male:
- white body with an ashy coating on top;
- black streaks at the ends of the wings.
Color of the female:
- body reddish with grey;
- lumbar region white.
Field harriers build their nests on the surface of the earth. The clutch consists of three to five white, slightly spotted eggs. They are smaller than chicken eggs, the most round.
The harrier is a migratory bird. It hunts by flying not very high, above the ground.
peregrine falcon
The most famous falcon. This is a rare and valuable bird breed. Unfortunately, poachers are especially fond of catching these particular predators, as a result of which their fate is extremely sad. Peregrine falcons are practically exterminated, they are very rare even in deserted areas.
In the United States, in order to restore the number of these birds, they kept in specialized enclosures. Peregrine falcon chicks are raised and then released to free latitudes. However, even taking into account the usefulness and importance of these activities, it should be said that they are very costly in material terms. Falcons released into the wild are of great monetary value.
A feature and pride of the peregrine falcon are clear, piercing black eyes, above which black superciliary arches loom. No wonder in Rus' the heroes were often called "clear falcons."
Within the Yamal territory, the number of falcons is no more than two hundred pairs of these birds of prey. The most populated part of Russia with falcons is the West Siberian tundra area, where the situation with predators is quite stable.
External characteristics of the peregrine falcon:
The falcon, by right, is ranked among the fastest living creatures on the planet, and even among birds it has no equal for a long time. He hunts, attacking the victim from above, in a steep "peak". Small birds, peregrine falcon grabs with strong paws, and larger ones, at speed knocks down with sharp claws on the hind fingers. Then the predatory falcon, on the fly, grabs the falling prey.
Peregrine falcons often bring their prey from places far from the nest. Previously, there was an opinion that they do not hunt near their nests, however, observations have shown the opposite. It is not uncommon for a falcon to hunt near a nesting female.
Predators of this species are very zealous and aggressive in protecting their nest. Noticing the danger, the peregrine falcon raises a frantic cry, and, diving, attacks the intruder. After a while, the female joins the male. Falcons also attack people, but with the aim of simply scaring them, without touching them.
The peregrine falcon is a sophisticated hunter. Among its victims can be identified entire collections of the most rare birds, the existence of which even ornithologists do not always know.
Falcons nest, choosing a variety of places for this. It can be rocks, strangers, abandoned nests, even hollow trees or just plain land. An important condition nesting is a possibility good review terrain. The clutch size is three to five eggs. They are similar in size to chickens.
Tellingly, the grown chicks do not eat small falcons, unlike Rough-legged Rough-legged Rough-legged Buzzards. This is considered a noble trait of this bird species. However, it is worth noting rightly that their number is absolutely independent of the harvest for rodents, which means that peregrine falcons with chicks will not die for sure from starvation.
Falcons are migratory non flocking birds leading a solitary lifestyle. One pair of peregrine falcons builds a nest away from the other. Pairs are permanent, stable. However, their nests are always in the same place. Predators arrive at the beginning of spring, and fly away at about the same time as other birds.
Derbnik
It is considered the smallest falcon in size. The nesting territory of this predator is extensive, but merlins avoid areas that are too northern. This type of predator is quite rare.
Food type of merlins - small birds, caught and captured on the fly. They build their nests mainly in trees, in abandoned crows' nests. The number of incubated eggs is up to five pieces. Both females and males act as hens, but the former participate to a greater extent.
It is noteworthy that the size of a derbnik is only the size of a dove. But at the same time it is a worthy predator in the tundra and its forests. This bird is protected by law.
Owls are nocturnal predators. These are known to all birds, which were repeatedly mentioned in children's fairy tales.
Features of the appearance of an owl:
Owls exterminate various rodents, while bringing great benefits to people. Therefore, they are protected by law from poachers and simply those who like to mock living beings.
Snowy owl (or white)
A very colorful nocturnal predator that lives in the steppes and tundra forests. Hunts for voles, partridges, hamsters - lemmings. Sometimes they catch hares and even arctic foxes and ermines.
The small peoples of the north often used owl meat for food, for this purpose they hunted it.
short-eared owl
In size inferior to the polar. It also feeds on rodents and lives in tundra areas. There were times when a short-eared owl was seen over the sea.
There are also other types of owls, for example: Lapland, hawk, eagle owl.
It is noteworthy that the tawny owl is a diurnal predator, even somewhat similar to a falcon.
Eagle owls are the largest birds from the order of owls. They have ears on their heads, the color is variegated with red. The eagle owl can attack a buzzard or a hawk, but basically its food consists of rodents and small animals.
In the conditions of the north, the eagle owl can conduct daytime hunting.
Birds of prey are usually called birds that hunt their prey in flight. Their characteristic features are excellent eyesight, as well as strong claws and a beak that serve to capture and kill a target. Hearing also plays an important role in the hunting of raptors.
- diurnal predatory;
- nocturnal predators.
Diurnal birds of prey include the families
- hawks;
- skopins;
- falcons;
- secretaries;
- american vultures.
Nocturnal birds of prey include a detachment of owls, in which two families are distinguished: owls and barn owls. The most famous representatives are owls(white, polar, eared, marsh, hawk and others), eagle owls, owls and owls (brownies, passerines and others), owls (bearded, long-tailed, gray), barn owls and scops.
Owl
Features of appearance and their impact on lifestyle
Almost all owls have common features. On a large head are large eyes, which appear even larger due to the plumage fanned around them. This is the front disk. They have a short curved beak, at the base of which are the nostrils.. These birds have dense and soft plumage, a rectangular tail, rather large rounded wings, with the help of which it quickly and silently plans and flies. The wings may differ depending on the species: in birds hunting in the forest, they are quite short, and in those looking for prey in open areas, they are long.
Feet and fingers are covered with feathers up to the claws, with the exception of fish owls. Due to the fact that the front fingers are reversible, owls can sit on branches, and the presence of long and sharp claws gives them the ability to firmly capture their prey. A striking feature that distinguishes them from other birds is the absence of goiter.
The color of owls is protective, it helps owls to disguise themselves against the background. environment and be virtually invisible during the daytime. Birds of prey of this species living in the forest have a brown shade of feathers, while those living in coniferous forests change to gray. Owls living on the plains have lighter feathers, and in the deserts they have a reddish hue. The color of males and females is always the same, with the exception of snowy owls. Males have a snow-white color, and females are motley, with a brownish tint.
Owls are nocturnal birds of prey; they have sharp eyesight and good hearing to hunt in the dark. Owls have large eyes that look forward, but the ability to turn their heads almost 180 degrees provides a wider field of view. Ears are on both sides of the facial disc, and not in all species they are symmetrical, may differ in size or be shifted up or down. These birds have a very large inner ear, as well as great amount neurons in the area responsible for hearing. Due to these features, owls perfectly hear their prey at night.
The lifestyle of most owls is nocturnal. The exceptions are the little owl and short-eared owl. The Arctic hawk and snowy owls hunt at night during the summer, and during the winter they seek food during the day. The remaining members of the owl family sleep during the day on branches, in rock crevices, in the attics of houses. Separate types build their nests in burrows or depressions in the ground.
Almost all species of owls live all their lives in one place and fiercely protect it from other birds, especially predators. However there are also species migrating for the winter e.g. short-eared owl. The rest can change their habitat only in the absence of food.
These birds feed on mice, rats, rabbits, earthworms, insects, snakes, fish, and crustaceans. On rare occasions, they may eat carrion. Mammals are caught on the fly, and fish are waiting, sitting on a branch above the water.
Owls are very talkative. In addition to the well-known hoot, their vocabulary includes a large number of other sounds, which they emit when they are hungry, protect the territory, during the breeding season, etc.
Owl breeding
The reproduction of these nocturnal predators is greatly influenced by favorable weather conditions and the availability of food. If these factors are met, then the breeding season comes earlier, there will be more eggs in the nest. Otherwise, there will be 2-3 eggs in the clutch.
Depending on the species, some owls create pairs for the rest of their lives, others form a new pair in each subsequent mating season. In most cases, nests of other birds are found for laying eggs., tree hollows, rock crevices. Some species use rodent burrows for this purpose or lay their eggs in the grass. They rarely build their own nests. By choosing appropriate place, within a few days the female lays up to 10-14 eggs. Incubation of chicks, depending on the species, lasts from 24 to 36 days and begins from the day the first egg is laid. Accordingly, the chicks appear within a few days. In the future, it is not uncommon for older chicks to take all the food in a difficult time, and the younger ones go hungry.
Helpless chicks are born eyes open at 2 weeks. First, the male brings food, and when the cubs grow up and more food is needed, the female also flies away to hunt. After 20-25 days, the owls get out of the nest. They fly poorly at first, so they do not move far from the nest.
The appearance and lifestyle of other nocturnal birds of prey are very similar to owls, although there are slight differences and features.
Birds, which prey on animals primarily through flight and attack from the air, use their senses, especially sight. They are defined as predator birds, primarily prey on vertebrates, including other birds. Their claws and beak tend to be relatively large, powerful, and adapted for tearing flesh. In most cases, females are significantly larger than males. The term "raptor" is derived from the Latin word rapere (meaning to capture or take by force), and may refer informally to all such hunters, or specifically to diurnal groups. Because their predatory lifestyle is often at the top of the food chain they encounter. many kinds birds of prey may be semi-predatory or fully predatory. However, in ornithology, the term "bird of prey" applies only to the feathered families listed below.
Definition.
Strictly speaking, the term predatory bird" has a broad meaning that includes many birds that hunt and feed on animals, as well as birds that feed on very small insects. In ornithology, there is a definition that is used here, this term has a narrower meaning for hunting birds, which have very good eyesight for finding food, strong legs with sharp claws for catching food, and a strong strong curved beak for tearing flesh. Majority carnivorous birds, also have strong curved claws for catching or killing prey. Predator birds tend to prey on vertebrates, which tend to be quite tall relative to the large size of the birds themselves. Most also feed on carrion, at least occasionally. Vultures and condors feed on carrion, which is their main food source. As an example, the narrower definition also excludes gulls and their birds of prey, which catch and eat fairly large fish, partly because these birds of prey catch and kill prey entirely with their beaks, and like skuas, feed on fish and vertebrates. With this cluster of morphological and behavioral characteristics, the species listed below tend to be carnivorous birds in ornithology. They can be divided into species that hunt during the day and those that hunt at night, for example. birds of prey and owls distantly related and classified into separate families, however, their evolution was convergent, both groups of birds adapted to a predatory lifestyle.
History of classification.
The taxonomy of Carl Linnaeus grouped birds (class Aves) into orders, families and species, with no formal rows between genera and orders. He placed everyone birds of prey into one order, subdivided into four genera: Vultur (vultures), Falco (eagles, hawks, falcons, etc.), Strix (owls), and Lanius (shrikes). This approach was followed by later authors such as Gmelin, Albany, and Turnton.
Classification, division into day and night predators.
Diurnal Birds of Prey, formally divided into five families (the traditional classification of the family, at present):
Accipitridae: hawks, eagles, buzzards, vultures;
Pandionidae: osprey (sometimes classified as a subfamily of the Pandioninae of the previous family);
Sagittariidae: secretary bird;
Falconidae: falcons, caracaras;
Cathartidae: vultures including condors.
nocturnal birds of prey, include such representatives as - owls - are classified separately, as members of two families that have come down to us, families:
Strigidae: typical owls;
Tytonidae: barn owls.
Observations indicate that otherwise unrelated groups of birds may serve similar ecological functions and contain many morphological similarities to each other, explained by the concept of convergent evolution.
common names.
Common names for various birds of prey are determined based on structure, but many traditional names do not reflect the evolutionary relationship between groups.
Falco rusticolus (gyrfalcon). The largest representative of the falcons in the world, the so-called "ghostly" Gyrfalcon, which received its nickname for its specific "smoky" color, is one of the most ferocious birds of prey in the upper latitudes of the Arctic.
Accipiter striatus. The smallest of the hawks North America. At the same time, he is the most daring and dexterous acrobat in the air. They have distinctive proportions: long legs, short wings, and very long tails, which they use to maneuver when hunting in dense groves, chasing birds and mice at breakneck speed.
- variable size, usually nocturnal birds of prey - specialized hunters. They fly almost silently thanks to special feather structures that reduce turbulence. They have a particularly acute hearing.
- is one of the largest, fastest and agile birds among both eagles in particular and birds of prey in general. Glittering golden feathers adorn the back of the head and neck; powerful beak and demonstrates his hunting prowess with his claws.
- as a rule, large birds of prey with long, wide wings, a powerful beak and massive legs, also have plumage on their legs. They build very large nests.
- a bird of prey of one species, found all over the world, specializes in catching fish and has paws adapted for this with curved claws. They build large nests, the diameter of which can reach 2 meters.
- have long wings and relatively weak legs. They spend a significant portion of their time in flight. They take live vertebrate prey but mainly feed on snakes.
are medium to large birds of prey with robust sense organs and broad wings, including members of the hawk genus (also known as "Buteo" in North America).
- big as hawks predator birds, with long tails and long thin legs. Most use a combination of keen sight and hearing to prey on small vertebrates, gliding on their long, wide wings and circling low over grasslands and swamps.
— predatory bird, scavengers, are divided into two distinct biological families: Accipitridae, which is found only in the Eastern Hemisphere, and American Vultures, which is found only in the Western Hemisphere. Members of both groups have heads partially or completely devoid of feathers.
— predatory bird, is a small slender falcon that preys on large insects and birds. Very powerful and fast bird.
Falconry, birds of prey video
From today, the day of Gerasim Grachevik, migratory birds are expected in Russia. Making long-distance flights, they return from warm countries. How are they oriented? Why are they flying like a wedge? What do they eat? We decided to answer these and other "bird" questions.
How to get directions
How not to make a mistake with the route? After all, a mistake will cost your life! But for cruise travelers this is not a problem at all: routes have long been defined and remain unchanged from year to year. Where to head, the younger generation will learn from older comrades. But what if there is only one inexperienced young in the flock? How to find out the way without a map and a gps navigator? It turns out that every bird has such a navigator, it is an innate instinct that leads the birds in the right direction. This is confirmed by cases when young individuals made their first flight absolutely independently.
Wind, wind, you are mighty!
Weather conditions certainly affect the course of migration. In warm weather, birds fly longer, and the flow of arriving birds increases dramatically. And if suddenly a severe cold snap sets in, the birds can even turn back to the south. During the autumn migration, a cold snap contributes to a faster departure. Ducks can move south without stopping, covering long distances - 150-200 km. The wind can interfere with the flight, and, conversely, contribute. Seagulls, flying rather slowly, fly in calm or with a fair wind. Naturally, with such an assistant, the flight is more intense.
Count in order!
Many birds fly in a wedge, such as cranes and geese. Some believe that birds fly like a wedge in order to cut through the air, just as the prow of a ship cuts through the waves. But it's not. The meaning of the wedge-shaped formation, however, like any other (rank, arc, oblique line), is that the birds do not fall into the vortex-like air currents created by the movements of the neighbors' wings. Due to the fact that birds in front flap their wings, additional lift is created for those flying behind. Geese thus save up to 20% of energy. At the same time, a great responsibility is assigned to the bird flying in front: it is a guide and guide for the entire flock. This is hard work: the sense organs and the nervous system are in constant tension. Therefore, the leading bird gets tired faster and is soon replaced by another.
Flight flight, and lunch on schedule!
During the flight, the flock will not always be able to fully eat - the possibilities for obtaining food are very limited. Where do you get the strength for such hard work? Gathering in long haul, we tend to think in advance about our diet. So the birds prefer to eat well on the track: in preparation for the flight, they eat very tightly in order to accumulate more fat reserves for a long flight.
Rest time, and flight hour
The flight is difficult, and the supply of energy quickly dries up, so it is very important for the birds to recuperate. Some species of birds fly almost without rest: a woodcock, for example, covers a distance of up to 500 km in one night without stopping. Others cannot boast of such endurance and make many stops. As a rule, the speed of these birds is small. They arrange a rest for themselves near the reservoirs, where they can recuperate, refresh themselves and quench their thirst. It takes a lot of time, and on average it takes about an hour to fly a day.
Wandering in the dark
Our travelers already have a lot of problems, and then there are the hunters! Rescues birds flocking lifestyle. So more likely to notice the attacking enemy. Pack mates are always signaling danger to each other. It is not a secret for hunters that it is much easier to get close to a single bird for a shot than to a group. However, detecting a flock during a flight is not so easy. Birds fly at a much higher altitude than usual, while managing to breathe rarefied frosty air.
Text: Nadezhda Timokhova
Infographics: Maria Zaitseva
Most species of migratory birds migrate at night, and these are mainly those that are active during the day. Obviously, nocturnal migration has its advantages, otherwise the behavior of birds would have changed long ago in the course of long evolution. Many diurnal birds flying at night can only get food during the day. Passerines, for example, always eat well before their non-stop flight over vast seas, which often takes the whole night. The only exceptions are long-distance diurnal passerine migrants, such as swallows, wagtails and pipits. Swallows, however, get food during the flight.
Many short-range passerine species migrate during the day. Distant migrants from this detachment fly at night, as during the day they are busy looking for food.
It is quite clear that the study of nocturnal bird migrations was not carried out as intensively as daytime ones. It is very possible that migratory birds and on dark nights they can distinguish the contours of land, lakes, rivers, as well as, for example, white ribbons of surf along the coast and the direction of white crests of waves on the surface of the sea. The surf can be heard as well as seen, even if the night migrants are flying high.
It could be assumed that the moon performs a function for night migrants similar to that of the sun for daytime migrants. However, back in the 1930s, it was found that the moon does not have a great influence on the flight of birds, this was subsequently confirmed using various methods. In recent years, the study of the orientation of birds during flights has shown that the moon does not really matter much for this.
Movement experiments with mallards, blue-winged teals, pintails, and Canada geese, which were released at night, provided with a small light bulb, showed that the birds immediately choose the right direction to their native habitat when the sky is cloudless. In cloudy weather, the mallards lost their orientation and almost fell into a panic. These experiments showed that birds can still navigate to some extent by the moon or stars. However, it should be taken into account that, for example, mallards are short-range migrants who do not make such record flights as distant migrants.
Experiments have shown that the species of birds studied were guided by the stars.
When the tested whitethroats of three species were shown pictures of the starry sky that did not correspond to the given time of the year during the periods of flights, the birds were confused. When they were shown the spring sky in autumn, they flew in the direction of the spring migration. If they saw the autumn sky in the spring, they flew south.
At least three night-migrating species of warblers seem to orient themselves by the stars, taking into account their position at the corresponding time of the year in a certain area. How birds establish the direction of flight is still unknown. Perhaps this mechanism is hereditary; while no one knows how the bird flies and where it will stop. Although the experiments were performed on captive-fed birds who had never seen the night sky before, they immediately chose the right direction without hesitation. Experiments with indigo bunting finches in North America have yielded interesting results, showing that constellation patterns at nesting sites are fixed in chicks and this manifests itself during their first flight.
A young bird is imprinted with a picture of the starry sky, with the help of which it sets the direction during the first flight. This, however, does not help to explain the reactions of the species to the starry sky patterns at more southern latitudes, which are observed during the first flight and which, for example, in experiments with the Accentor Warbler, lead to a change in course. The fact that nocturnal migrants kept in cages choose the direction of flight corresponding to a given time of year and a given area was confirmed by the example of 12 other species of birds.
The fact that migratory birds can fly considerable distances in the absence of visibility, maintaining a certain direction and at the same time taking into account wind drift, is one of the remarkable discoveries made with the help of radar. How is the orientation of birds carried out during such a "blind" flight? Perhaps acoustic means of orientation help here.
As a rule, birds fly silently, without drowning out the sounds coming from outside. It is believed that birds can perceive sounds at much higher altitudes compared to the capabilities of human hearing. With the help of balloons, it was possible to register sounds emanating from the earth's surface at night at considerable heights. At the same time, it was found that, for example, the noise of a train is heard over 6400 m, the rumble of Niagara Falls is over 4500 m, the barking of dogs is over 1800, the voices of people, the croaking of frogs and the noise of current waters are over 1000, the chirping of crickets is over 750, the sound of sea waves is over 100 m, etc.
Night migrants over Louisiana, as it turned out, fly at altitudes from 250 to 2400 m. Apparently, they easily perceive different sounds from the earth's surface.
Many birds migrating at night make occasional call calls, which are of orientational value and, in addition, apparently help to keep the flock closed or to communicate with other birds of the same species. It has been observed that birds often give voices in cloudy or foggy weather, when these sounds are also best heard. The intensity of calls also increases during flights along the coast.
It has been suggested that birds make voices during night flights in order to catch the echo from the earth's surface. Controlled balloons perceive the echo from their own sound after 8 seconds at an altitude of about 1300 m.
Thus, it has been established that birds receive and use sound information from the earth's surface, but it has not been clarified in what way this information is processed in order to orient the flight in a certain direction.
How do young long-distance migrants find their wintering grounds during their first flight?
The readiness of a bird for flight largely depends on internal physiological factors. If their influence stops on the way, migration is interrupted, of course, provided that the bird ends up in a place where there are suitable ecological conditions for it.
Previously, it was pointed out that in young birds during their first migration, the end of migration is associated with reaching the wintering grounds; consequently, the influence of the environment in these places determines the termination of the flight. But it also happens the other way around: the time and place of the end of the flight can be determined by a time mechanism finely arranged for distant migrants, and it is precisely this mechanism that can predetermine the “choice” of wintering sites.
Evidence for this hypothesis has recently been presented. A clear temporal relationship was found between the duration of the migratory disturbance period in these species and the distance they usually fly in autumn. A similar picture was also found in experiments with the Chiffchaff. The mentioned species migrate at different distances - from 250 km (Sardinian warbler) to 5 thousand km (garden warbler), which, of course, also determines very significant differences in the duration of migratory disturbance in the corresponding species. This means that the long-distance migration of birds is predetermined in time; it stops at the moment when the birds reach a certain wintering place. Not only each species, but also different populations of specific bird species, differ in the duration of internal and inherited temporal mechanisms on which the distance of flight depends.
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