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Cormorants

Cormorants

The cormorant family includes about thirty species of birds. These birds are marine and freshwater, and therefore nature has endowed them with an elongated body.

Cormorants have a thin and long beak, which forms a large sharp hook at the end. Such a device is necessary for cormorants to find food - for successful fishing. Cormorants have a long neck. Cormorants are endowed with webbed feet, which are located far behind.

The color of the plumage of cormorants is black, it is characterized by the presence of a metallic shade. Cormorants are silent birds, but their voice can be heard in the colonies formed at the nesting sites (as a rule, cormorants nest together with other birds). When building a nest, cormorants use grass and branches. The clutch contains four to six eggs that have a matte finish.

Twice a year, these birds change their plumage - incomplete molt at the beginning of the year and complete molt, which begins with the arrival of summer and continues until the end of autumn. Incomplete molt is also called prenuptial, and full molt is postnuptial.

Chicks are born naked and blind, over time their body is covered with fluff. Newly born cormorants start flying at seven weeks or eight weeks of age. Sexual dimorphism in cormorants usually comes down to size differences between females and males. The latter are larger.

Cormorants are widespread. Representatives of this family, both in cold and temperate latitudes, are migratory species. They are also found in hot countries - they are sedentary species. Cormorants inhabit almost all large rivers and seas, they can often be seen near many lakes of our planet. Some cormorants live in wetlands. Thus, cormorants are widespread throughout the globe. The greatest biological diversity is observed in temperate and tropical climates. These are the great cormorant, the lesser cormorant (inhabits the Caspian Sea), the Bering cormorant, the Ussuri cormorant, the red-faced cormorant and the crested cormorant (inhabits the Kola Peninsula). The most common of these is the cormorant. It inhabits the territories of Eurasia - from the Atlantic to the Pacific coast. Crested and cormorants are rare species. They are listed in the Red Book of Russia.

Black plumage is characteristic of cormorants. True, it has a metallic luster. Some cormorant species have a different color from this one. For example, in the case of the red-footed cormorant, it is gray, and the belly of the variegated cormorant is white (as in several other species of these birds). There is a small patch of bare skin on the front of the cormorant's head. In different species of these birds, it can be black, red, blue or yellow. In addition, young cormorants have lighter plumage. Their plumage color is light brown.

Cormorants are medium to large birds. The weight of large individuals can reach four kilograms. The wingspan of cormorants can reach one hundred and sixty centimeters, and the body length is one meter.

Cormorants are excellent divers. These birds swim using only their legs, while at the same time they make not weak pushes with both paws. The steering function is performed by the rigid tail of these birds, as well as, to some extent, their half-spread wings. Cormorants can stay underwater for one or two minutes. However, they are able to dive to a depth of twenty-five meters. After diving and underwater hunting, the plumage of these birds gets significantly wet (which, in principle, is an amazing fact). Therefore, cormorants are forced to dry it for a long time. At the same time, they rest either in the trees, or simply on the shore, spreading their wings.

Cormorants are difficult to take off from the earth's surface. These birds practically cannot do this, it is much easier for them to take off from rocks or trees. Cormorants can take off from the water, but for this they need a long takeoff run. These birds fly in a formation specific to them - this is a line. The flight of cormorants is not only straightforward, but also very fast. The profile of a flying cormorant resembles an even cross.

Cormorants nest colonially. Moreover, one settlement often includes not even thousands, but millions of individuals. Cormorants are considered silent birds by nature. However, gathering in huge colonies, they almost all the time give a croaking rattling voice. As a rule, cormorants nest together with other birds. And even with animals (for example, cats). As for birds, they can be colonial birds such as penguins and gulls.

Cormorants are nomadic birds. Indeed, many species make not only seasonal migrations, but also significant daily flights. But not all cormorants are migratory birds. For example, the species of cormorants living on the Galapagos Islands (Galapagos cormorants) have completely lost the ability to fly. This bird, of course, has wings. However, they are very short, in connection with which the Galapagos cormorant is physically unable to lift itself into the air. The reason for this loss is that on those small islands where these birds live, they have no enemies at all. On the Commander Islands up to the nineteenth century, another flightless species of cormorants lived - the steller cormorant, but it became extinct.

A wide variety of conditions are suitable for building a nest. These birds can arrange their nests both in reeds and on level places, both on trees and on rocks. The clutch contains four to six eggs. The eggs have a matte surface. They have a bluish background, which is varied by white smudges.

The cormorant chicks that have been born are completely helpless. They are born naked - no plumage. Its appearance in different chicks is marked at different times. The period to feathering can range from thirty-five to eighty days. Often, parents feed their chicks after they have fledged, and this can continue for another 2-4 months. As for the adult plumage, it appears in young cormorants in the period from one to four years (depending on the species). An interesting fact is that the size of the hatched chicks is different from each other. This is due to the fact that eggs are not laid simultaneously, but one by one. The incubation period lasts twenty four to thirty one days.

The diet mainly includes fish. Freshwater cormorants also diversify it with frogs and crayfish. For many cormorants, collective hunting is characteristic, and not only within the species, but also together, for example, with pelicans. When fishing, they drive it to shallow water. On average, a cormorant consumes from three to four hundred grams of fish per day.

For centuries, the Chinese and Japanese have used cormorants for fishing. And although at present in Japan this is no longer practical, it remains as a tourist attraction. It is possible to observe the centuries-old tradition and participate in its embodiment in reality in two places - on the Tamagwa and Nagara rivers. By the light of torches from a raft or boat at night fishing is carried out - the fish rises to the light. At some point, the prepared cormorants are released. This means that rings are put on their necks and a short cord is attached. Cormorant dives for prey and floats to the surface with it. The ring is necessary just so that the bird does not immediately swallow the caught fish. With the help of five to ten cormorants, it is possible to catch a whole basket of fish in just a few hours, while also getting great pleasure.

Cormorants are useful to humans not only through fishing. For example, Bougainville's cormorant is the main "producer" of guano. Guano is bird droppings that are considered to be a very valuable fertilizer. This cormorant en masse inhabits the coast of Peru, and in some places the layer of guano reaches fifty meters. It is worth noting the fact that the guano deposits began to be developed industrially only in the middle of the nineteenth century. At the same time, they were developed in the distant past by the ancient Incas.

The great cormorant living in Russia is a large bird. The wing length of the great cormorant varies from thirty-three to thirty-eight centimeters, and the average weight is three kilograms. In size, males are slightly larger than females. The cormorant is characterized by the presence of a large white half-ring on the underside of the head, and the bare parts of the head are yellow.

Great cormorant is a bird with a wide distribution area. The great cormorant is found in vast territories of both Europe and Asia, while the nesting area continues to New Zealand, Tasmania and Australia, and covers many areas of the African continent. An interesting fact is that only the territory of Greenland is currently a nesting place for this bird in the entire western hemisphere. Individuals nesting in the southernmost parts of the range, as well as in the northern parts, are migratory - wintering occurs in North Africa and the Mediterranean. Great cormorant is a sedentary bird if the territory of warm latitudes becomes a nesting place. These birds arrive at nesting sites in Russia with the first spring warming. For example, in February they can be found in the Volga delta. If the winter cold returns, then the cormorants may well go back.

Great cormorants are monogamous. These birds already come in close-knit pairs to nesting places. Probably, cormorants form pairs for life. A significant number of cormorants begin nesting for the first time at the age of three. For some individuals, this occurs at the age of four, or even happens to be five, years old. Two-year-old cormorants, which are not yet sexually mature, arrive at their native colony. Here they keep close to adult cormorants.

Sometimes cormorants use heron nests, while dragging them into trees. But this rarely happens - as a rule, these birds independently equip their nests. Construction begins with the construction of the base of the nest. It is formed from large and thick branches. Above the cormorants lay thinner branches. Often, the branches are so fresh that they retain green leaves. Groups of cormorants leave us to collect nesting material in the early morning, usually a bird brings only one branch at a time. The result of such a construction (in which both the male and the female take part, and completely on equal terms) becomes a turret, the height of which can range from fifty to one hundred centimeters. Often, such turrets are located very close to each other - almost closely.

The period from April to June is the time for cormorants to lay their eggs. In Western European territory, it happens that this period extends to September. There is only one clutch per year. An exception is the circumstance when the masonry is ruined. In this case, additional masonry is possible. Typically, a full clutch contains five eggs. They have a pale brownish-green color (however, it is very difficult to recognize, the reason for it is the contamination of their surface with droppings) and an oval-elongated shape. The average cormorant eggs are 64 x 39.5 mm. However, in all eggs, they vary in one direction or another. In some cormorant colonies, a circumstance was discovered in which one of the eggs in the clutch turned out to be unfertilized. This was especially true for those clutches that contained five or six eggs. Both the female and the male take part in incubation. In the Volga delta, the period of incubation for cormorants is either twenty-eight or twenty-nine days. As for cormorants nesting in Western Europe, individuals incubate eggs here for twenty-three or twenty-four days. The start of incubation may depend on local conditions. Newborn chicks are helpless - they are blind (eyes open on the third or fourth day of life) and naked (fluff will cover their body only after two weeks). Juveniles leave the parental nest seven weeks after birth, although the first excursions from the nest begin much earlier. Cormorants are considered independent after reaching the age of twelve to thirteen weeks, after which these birds huddle in flocks. The flocks are small at first. With this composition, young individuals roam near nesting sites. Over time, the number of birds in flocks increases significantly. As soon as this happened, the cormorants begin to fly away.

Cormorant is easy to "circle around the finger". This is often done by the hooded crow. When the cormorant is incubating eggs, a crow appears in the immediate vicinity. By nature, a crow is weaker than a cormorant, so he tries to hit her with his beak. True, it does not reach. The hooded crow's obsession causes the cormorant, determined to deliver a crushing blow, to its feet. It turns out that the crow actually needs it - it flies away calmly. But behind the cormorant, indeed, during all this time, danger awaited. As soon as the cormorant rises from the eggs, the crow's partner picks up the egg, with which it flies away.

The Lesser Cormorant is the smallest cormorant inhabiting the territory of Europe. Its body length is on average forty-eight centimeters, and its weight barely reaches eight hundred grams. Thus, the size of the cormorant is at least half the size of the cormorant. The cormorant has a short beak. The European population of this species numbers about one thousand pairs. The diet of the cormorant includes small fish, which this bird catches in shallow water.

Lesser cormorants are confined to inland freshwater bodies. Often these are reservoirs that are located in areas characterized by the presence of a warm climate. They prefer reservoirs overgrown with inundated vegetation. Cormorants build their nests either in reed beds or in trees. The lesser cormorant is a colonial bird. Moreover, the number of individuals in colonies can be enormous - one colony can contain from tens to hundreds of nests. If a small cormorant equips a nest on a tree standing in the water, then it is often a neighbor of herons and ibises. Young individuals leave the parental nest even before they are able to fly. Cormorants fly on the wing at about ten weeks of age.

Cormorants are migratory birds. In large flocks, they go south immediately after the end of the nesting period. The wintering grounds for these birds are in the Mediterranean. In winter, they can also be found in salt water bodies. Cormorants arrive at nesting sites around the beginning of March. A clutch of cormorants contains three or four eggs. Their length is forty-seven millimeters. At the beginning of May, as a rule, cormorants have already finished laying their eggs and start hatching, which lasts from twenty seven to twenty nine days. Young cormorants become independent at about forty days of age. If they are in danger, cormorant chicks can jump out of the nest early enough. Moreover, many of them are even able to swim.

The variegated cormorant has a variegated color. The color of the representatives of this species is significantly lighter than that of the rest.The upper part of the body is black, but the lower part (down to the cheeks) is white. A yellowish spot adorns the gap between the beak and the eyes, and the area around the eyes is blue. The chin of the motley cormorant is reddish. It is such a variety of colors that gave the name to this type of bird. Variegated cormorants live in New Zealand and Australia.

Variegated cormorants settle along the coasts of the seas. They really prefer them. However, variegated cormorants are often found on the shores of rivers and lakes, however, if the water level in them is constant. Spotted cormorants are colonial birds. There can be several thousand nests within one colony. Mostly nests are built on shrubs and trees.

Clutch of variegated cormorant contains three eggs. Incubation continues for four weeks, and both the female and the male take part in it. Chicks are born helpless and feed on their parents in the nest for seven or eight weeks. After this period, care for the offspring does not end, but lasts about eleven more weeks.

The crested cormorant is a rare species. In Russia, the crested cormorant (aka long-nosed cormorant) is found only on the territory of the Kola Peninsula. In addition, the crested cormorant can be found on the Northwest African coast, in the Mediterranean Sea, along the European Atlantic coast, as well as in Iceland. All nests of these birds are under close supervision and protection on the territory of Russia.

The crested cormorant is a seabird. Moreover, the crested cormorant spends a significant part of the time over sea waters (not far from the coast). On land, this bird can be seen only during the nesting period. Only fish is included in the diet of the crested cormorant.

At nesting sites, crested cormorants form colonies. This is most often the case. However, there are times when these birds nest in separate pairs. At the same time, they build a nest in rather hard-to-reach places. This can be, for example, rocks or a mound of stones. Cormorants use dry grass or algae as building materials. In this regard, branches of a juniper or willow may also suit them. Crested cormorants use one nest for several years. The clutch contains two to five white eggs. Both partners are involved in incubation.

Long-eared cormorants are large birds. Their body length ranges from seventy to ninety centimeters, their weight reaches two and a half kilograms. They have a long beak. Females of eared cormorants are somewhat smaller than males. The average lifespan of eared cormorants is six years. To be more precise, 6.1 years. However, the life expectancy of 17 years and 9 months was also recorded - that is how much it was for the oldest known cormorant.

Watch the video: Fishing Birds in China (October 2020).