Order Toadstools Podicipediformes

Grebes are a well-defined order of birds, with one family (Podicipedidae), four or six genera (Rollandia, Tachybaptus, Podilymbus, Poliocephalus, Podiceps and Aechmophorus) and 17 or 21 species. Distributed everywhere except the Arctic, Antarctic and oceanic islands. In the Old World - only Tachybaptus and Podiceps, in the New - Podiceps and other four genera. Most species of toadstools are found in America: North - seven, South - eight. There are five species in the fauna of the USSR. The genus Tachybaptus, which includes our little grebe ruficollis and three other species of the Southern Hemisphere, together with Podilymbus, differs from other grebes in the structure of the tarsus skeleton, voice, marriage ceremony, and lifestyle. These two genera are combined into the tribe Podilymbini. Six species of the genus Podiceps, and possibly all other toadstool genera except Rollandia, are in the tribe Podicipedini.

The relationship of grebes with other modern and fossil orders of birds is unclear. Neither the classical methods of morphology and systematics, nor the study of egg proteins give anything at the same time. In the class system, they stand apart and are usually placed at the very beginning of it. In the fossil state, real Podiceps are already known, the most ancient of which were found only in the Lower Miocene of the USA. Grebes are a relatively young, highly specialized order of birds. They separated from their still unclear ancestors, probably somewhere in the Paleogene, and quickly adapted to an aquatic lifestyle in fresh water. The proximity of grebes to loons is apparent, roughly convergent, due to a similar external appearance, associated with deep diving adaptations. In fact, there are cardinal morphological differences between these orders, shown by M. Stolpe, E. N. Kurochkin, B. K. Shtegman, and L. P. Korzun. There are also significant differences between them in ecology. Therefore, the old position, according to which the origin of grebes and loons was considered common and united in one detachment or considered them to be closely related detachments, has been left in all serious modern reports.

The size of the toadstools is small and medium, their body is dense, elongated, the neck is long (relatively longer than that of the loons), the hind limbs are carried back, only the tarsus with paws protrude from under the general skin, the legs are pressed by the muscles along the body, tail tail feathers reduced, wings narrow but not short. The general type of coloration is dark above, light below, with a few exceptions. On the head in the wedding dress, many develop decorating feathers. Males and females are colored similarly. The skull is schizognathic, saline-excreting supraorbital glands are almost not developed. The beak is long, sharp or short thickened. There are 17–21 cervical vertebrae; the last four thoracic vertebrae fuse into the dorsal bone. The sternum is expanded and relatively short (unlike loons), the patella is large and elongated, but does not fuse with the knemial crests of tibiotarsus (unlike loons), the tarsometatarsus is laterally compressed, one or two rows of serrated scutes pass along the posterior edge of the tarsus (in different from loons).

The swimming membrane is split - each finger has a separate leathery blade (unlike loons), the muscles of the hind limbs are very powerful, but do not have nine muscles from their full set in birds (unlike loons, which have an almost complete set of muscles of the hind limbs). There is no goiter, the stomach is elongated with thin walls, the blind intestines are small. The coccygeal gland is feathered. The plumage is dense and dense, the feathers have a weak secondary trunk, the apteria occupy a very small area, the bridle is not feathered (unlike the loons). Primary primaries - 12, secondary - 17–22. The molting of the primaries is simultaneous, with the loss of the ability to fly. The downy outfit is replaced by one chick, an adult outfit is acquired in the second calendar year.

Grebes are diurnal and nocturnal birds, they apparently feed only during the day, and are active at night during the mating season and during the migration season, flying during migrations exclusively at night. The flight is fast, straight, they cannot maneuver in the air. They take off from the water with difficulty and reluctantly, after a long run, they cannot take off from land. Most of their lives are spent afloat. They dive great. They usually spend under water during feeding for about 30 seconds, but they can stay up to 3 minutes. They feed normally at a shallow depth of 1-1.5 m, but they got into the nets at depths of up to 25 m. Cruising speed under water is up to 3 m / s. They move in the water column exclusively with the help of their legs.

An elongated body, a long thin neck, an elongated tibia and tarsus, powerful muscles of the hind limbs, shortened thigh and middle toe, and uneven lobes of the fingers (Fig. 21) enable the grebes to effectively dive, feed, and swim in the water column [Onno, 1959; Kurochkin, 1967].

Figure 21.
a - during the stroke (rear view), b - during the removal forward (side view)

Such work of the paws of grebes is due to the special arrangement of the muscles and joints of the hind limbs, which rotate the tibiotarsus along the longitudinal axis by 120 °, and with it the tarsus with the paw. The unevenness of the blades of the fingers is important. The inner edge of the blades is much wider than the outer. Therefore, both when pushing and when bringing the paw to the body after the push, the blades rotate around the longitudinal axis at an angle to the direction of movement (this becomes possible due to the special articulation of the phalanges of the fingers with the blocks of the tarsus), which creates a lifting force that develops with muscular effort, significantly increasing the speed of movement paws and pushing power. A greater number of individual strokes per unit time increases the speed of the bird in the water column. It is significant that the toadstool's paw acts under water largely automatically, with minimal expenditure of muscular energy in the individual phases of the stroke [Kurochkin, Vasiliev, 1966; Kurochkin, 1971, 1972]. On land, grebes can hardly move. Only the western grebe Achmophorus occidentalis is known to be able to walk on solid substrate and build nests at a considerable distance from water.

Most species of grebes live all their lives sedentary on fresh inland waters. Species of the genus Podiceps during migration and wintering go to coastal marine areas. Settlement of Rollandia micropterum on the lake. Titicaca in South America has led to a significant reduction in wings, these birds cannot fly.

For nesting, grebes, as a rule, choose small fresh water bodies covered with dense emersed vegetation. Many species nest together, forming colonies up to several dozen nests, often on the periphery of a colony of gulls and terns or near individual nests of coots. Most of the nests are built floating, usually about two or three large stems of aquatic plants, they are placed secretly among the vegetation, but nests can also be located in open water. Rarely the nests are free-floating, more often the bases touch the bottom. They rarely build nests on the shore of a reservoir at the water's edge or on a hummock. They always build several nests at once, both partners participate in this, but only one, usually the last, is used for laying eggs, the rest serve for rest and mating. Characteristically, grebes cannot mate on water. They have a complex and varied ritual of marriage ceremonies. Mating also has its own ritual. It is also ritually comfortable behavior - cleaning and straightening the plumage, touching the chest after diving, which removes water from the beak. The latter may be due to the absence of supraorbital glands in grebes.

In clutch from two to 10 eggs. Freshly laid eggs are white with a chalky surface, but after a day or two they acquire a greenish or brown tint, stained with wet nest material; the color becomes thicker as it incubates. Eggs are laid at intervals of a day or two, incubation begins with the second egg and lasts 20–28 days. Chicks hatch at different times. Immediately after hatching, the chicks climb onto the back of their parents, and so they wear them all the first time. They often feed on their backs, and some may dive with chicks on their backs.

They feed on aquatic insects, crustaceans, mollusks and fish, sometimes the stomachs are filled with algae, such as char. Prey is caught in the water column, on the surface of the water and above the water, collecting insects from plants and even grabbing in the air. They capture the prey with the tip of the beak, when swallowing it, the branches of the lower jaw are automatically parted to the sides (streptognathism), which makes it possible to swallow larger objects whole; these grebes differ significantly from loons. In wintering areas, grebes become almost completely piscivorous, while in the nesting period, the majority of food in the majority is invertebrates. The degree of fish-eating is different in different species, and in some species it also varies geographically. In the stomachs of grebes from the first day of life (obtained from feeding from parents) contains small covering feathers of these same birds. The importance of feathers in their digestion was determined in different ways. In fact, feathers provide the formation of pellets from invertebrate chitin, bones and fish scales. Regurgitation of pellets has been established for Podilymbus podiceps, Great Grebe and Red-necked Grebe. After regurgitating the pellet into the water, the bird collects the released feathers again and eats them.

Toadstools have some economic importance. Although the basis of their diet in most places is aquatic invertebrates, in some conditions the great grebe, eastern gray-cheeked grebe, little grebe and Aechmophorus can be considered conditionally harmful, settling in fish farms. But, as shown by special calculations, the percentage of juvenile fish eaten by them is tenths, and therefore their real harm becomes imaginary. During wintering, large species switch to fish in their diet, but at the same time they consume mainly small non-commercial species - small herring, sculpins, stickleback, blennies, gerbils, etc.

Grebes do not have commercial value as waterfowl due to the poor quality of their meat, although everywhere they are hunted little by little along with ducks and coots. There is no demand for "bird fur" now, but in the 19th century. the extermination of grebes for this purpose in Europe was catastrophic.

In modern conditions, grebes have become important as a biological indicator of the degree of pollution of fresh water bodies with pesticides and heavy metals. As fairly large and completely aquatic predators, they have become the last link accumulating harmful substances and elements in the ecological chains of inland waters.

They can dive for 10-40 seconds, have a disgusting taste of meat with the smell of fish.

(podicipediformes) consists of one family (Podicipedidae), six genera, and 22 species (two extinct: Podilymbus gigas, Podiceps andinus).

toadstools(Podicipediformes) are a group of medium-sized freshwater waterfowl that inhabit wetlands, lakes, ponds, and slow-flowing rivers in most regions of the world, with a few exceptions such as the Arctic, Antarctic, and some oceanic islands. Grebes are experienced swimmers and excellent divers. They have rounded, narrow toes, a stocky body, and blunt-shaped wings. Grebes have a long neck and a sharp beak.

toadstools distributed almost all over the world (absent in the Arctic, Antarctic, some oceanic islands).

Grebes inhabit freshwater ponds, lakes, and slowly flowing rivers (up to 3,000 meters above sea level). Northern populations migrate to large inland waters, estuaries, or coastal waters for survival during the winter months.

toadstools have a narrow but strong body, as they are waterfowl. The main color of the plumage is gray, on the sides from brown to black, the abdomen has a white or light shade. Males are often smaller than females. Sexual dimorphism may occur in the coloration of the plumage of the head or neck and feathers. Grebes are medium to large in size (22-76 cm), with a moderately long beak, short wings (12 primaries; 15-21 secondary), and a vestigial tail that lacks stiff feathers. Other signs include: the pupil may be scarlet, yellow, or brown; nostrils have shallow paths; the nasal septum is absent; 3-6 thoracic vertebrae. They also have their feet far behind. Three toes in front, separate, big toe present in most species. The toenails are wide and flat, the feet are comb-shaped.

toadstools prey on fish, aquatic insects, crustaceans, molluscs and small vertebrates. Fish catch includes: eel (Anguilla), roach (Rutilus), tench (Tinka), minnow (Phoxinus), trout (Salmo trutta), perch (Perca fluviatilis), herring (Clupea), needlefish (Signathus), blenny (Zoarces) , goby (Gobius), and cod (Gadus). The insects they eat are mayflies (Ephemoptera), stoneflies (Plecoptera), dragonflies (Odonata), waterbugs (Hemiptera) and ground beetles (Carabidae, Ditiscidae). Other invertebrate prey includes: mollluscs, snails (Lymnaea, Valvata), shrimp (Gammarus, Artemia) and crayfish (Astacus).

During the breeding season, grebes take part in courtship displays. Some species swim side by side in the water, and as soon as they pick up speed, they raise their bodies to a vertical position. toadstools- attentive parents, both males and females help the chicks. Both parents participate in nest building and help each other during the incubation period (21-30 days, one or two eggs are laid). Both parents also feed the young and carry the chicks on their backs. covered with dense plumage. They have developed sense organs, but depend on adults for feeding, warmth, and protection. Chicks can beg and behave peacefully.

Young toadstool chicks become independent and feathered in 6-12 weeks. Some grebes molt before or at the end of the breeding season, while others molt during migration.

Slightly concave nests of aquatic vegetation float in shallow water, tied to the roots of aquatic plants. Territorially nests of grebes are usually dispersed and hidden places, while in colonies (up to several hundred pairs) nests can be located one meter apart. The eggs are white or cream and the number ranges from two to seven eggs. Females lay one egg every one or two days. Some species may raise two or three litters per season. Some breeds breed all year round, while other breeds breed seasonally (three to six months). Seasonal breeding may synchronize with annual floods or the growth of emersed vegetation.

toadstools excellent divers and powerful underwater swimmers. However, the legs are far behind the body, and grebes are not able to move quickly on the ground. To take off, grebes rapidly beat their wings as they run through the water.

During the breeding season, grebes are found in pairs or families. During wintering, migratory birds live in groups, forming flocks of hundreds or thousands at migratory stops and wintering grounds.

While some grebes are very vocal, others are almost silent, even during the breeding season. Many grebes can make 10-12 sounds. Sounds range from whistles and howls to simple screams.

Today, grebes are hunted or caught primarily for food. By the turn of the century, however, tens of thousands of grebes were shot for their furs.

evolutionary history toadstools, remains unclear. An analysis of morphological characters suggests that grebes may be related to waterfowl, collectively forming groups related to Sphenisciformes (penguins). Conversely, DNA hybridization suggests that grebes are related to diverse families including: phaetons, cormorants, pelicans, herons, vultures, storks, penguins, and loons.

Toadstool fossils described from the Tertiary Period: Early Miocene fossil from Oregon (Podiceps oligocaneus); Miocene, fossils from Spain (Thiornis sociata); and Lower Miocene, fossils (Miobaptus walteri) from former Czechoslovakia.

Taxonomy

• Genus Tachybaptus
  • Lesser Grebe, Tachybaptus ruficollis
  • Australasian grebe, Tachybaptus novaehollandiae
  • Madagascar grebe, Tachybaptus pelzelnii
  • Alaotra grebe, Tachybaptus rufolavatus - extinct (2010)
  • Grebe, Tachybaptus dominicus

• Genus Podilymbus
  • Pied grebe, Podilymbus podiceps
  • Atitlán grebe, Podilymbus gigas - extinct (1989)

• Genus Rollandia
  • White-crested grebe, Rollandia rolland
  • Titicaca grebe, Rollandia microptera

• Genus Poliocephalus
  • Grey-headed grebe, Poliocephalus poliocephalus
  • New Zealand Grebe, Poliocephalus rufopectus

• Genus Podiceps
  • Grey-cheeked grebe, Podiceps grisegena
  • Great Crested Grebe, Podiceps cristatus
  • Horned Grebe or Slavic Grebe, Podiceps auritus
  • Black-necked Grebe or Marsh Grebe, Podiceps nigricollis
  • Colombian grebe, Podiceps andinus - extinct (1977)
  • Great grebe, Podiceps major
  • Silver grebe, Podiceps occipitalis
  • Junin Grebe, Podiceps taczanowskii
  • Grebe, Podiceps gallardoi

• Genus Aechmophorus
  • Western Grebe, Aechmophorus occidentalis
  • Clark's Grebe, Aechmophorus clarkii

— waterfowl and good divers. And they are often mistaken for ducks, they have nothing to do with the latter. In addition to being different from ducks in appearance, they also sit much deeper on the water; this is due to the fact that the bones of grebes, unlike many other birds, are mostly not hollow and are less filled with air.

Strong short legs are carried far back relative to the body; they help grebes to swim and dive well. The toes are not connected by membranes, but are trimmed on the sides with hard skin blades up to a centimeter wide, no less convenient for rowing. In this case, three fingers are directed forward, and the fourth - back. With their feet, grebes do not row under themselves, like, for example, ducks or gulls. The legs work very effectively from behind, forming a kind of ship's propeller.

Birds dive in one sharp throw, head first. In this case, the body sometimes rises completely out of the water. With such a jump, grebes manage to dive at an almost right angle and dive to great depths. In this case, the wings remain tightly pressed to the body, i.e. Grebes do not use them underwater for movement, like penguins or loons do.

They usually dive for 10 - 40 seconds, while smaller species of grebes, on average, linger less under water than large ones. There have been cases of birds submerging under water for one minute, and a maximum submersion time of three minutes has been recorded in the red-necked grebe. The immersion depth is usually 1 - 4 m, but there is a case of finding a toadstool entangled in a net at a depth of 30 m. Representatives of this family are able to overcome quite long distances under water in a horizontal direction.

Although the legs carried back help grebes to move excellently in water, they are practically unsuitable for walking on land. As a rule, birds leave the water only to rest or on their way to the nest. At the same time, on land, representatives of this family are rather clumsy and move, holding the body almost vertically.

They take off relatively hard: in order to lift their heavy body into the air, grebes scatter over the water for a long time, while helping themselves with their wings. In case of danger, they prefer not to take off, but to dive. Once in the air, birds fly well and can travel long distances.

Some species of grebes are migratory. The short-winged rollandia, Tachanovsky's flightless grebe, and the extinct Atitlan grebe have lost their ability to fly. Since there are almost no grebes on land, plumage has to be cleaned and lubricated on the water. While doing this, they lie first on one side, then on the other. Frozen in cold water, the legs do not warm like ducks, hiding them in the plumage of the abdomen, but lifting them out of the water to the side.

The soft, dense plumage of grebes has water-repellent properties. Each grebe has an average of over 20,000 feathers. They stick out of the skin at an almost right angle, slightly twisted at the ends. By pressing the feathers against the body, grebes can regulate their buoyancy. Often they swim, almost completely submerged in water, while only the head and neck remain above the water.

During the year, most species undergo noticeable changes in plumage. In the mating season, outfits are distinguished by bright colors on the neck and head, noticeable tufts, collars, tassels combed back, and sideburns on the cheeks appear. In illegitimate attire, on the contrary, gray and brown colors prevail. There is no pronounced sexual dimorphism in grebes; males can sometimes be noted to have brighter colors in plumage, and on average they are slightly larger than females. In any case, these differences are not enough to distinguish in the wild.

The sizes of grebes range from 23 to 74 cm, weight - on average from 120 to 1500 g. There are two main types of grebes: with long, sharp beaks that feed mainly on fish and have long necks, while species that feed on aquatic arthropods have shorter necks and beaks. The extinct Atitlan grebe had a beak that was perfect for catching crustaceans.

Toadstools are distributed on all continents except Antarctica. They live in tropical, temperate and subpolar regions. Only the red-necked grebe is found north of the Arctic Circle; grebes, unlike loons, have not mastered the distant polar regions. The ranges of some species of grebe are limited to individual islands, such as Madagascar or New Zealand.

Three species of toadstools living in South America have extremely small ranges: each species has only one lake of its own. Living on Lake Titicaca, located on the border of Peru and Bolivia, a small brown, with a reddish crest, the short-nosed rollandia has completely forgotten how to fly, so it cannot move somewhere on its own. The Atitlán grebe, which lived on Lake Atitlán in Guatemala, also had underdeveloped wings. Therefore, she never parted with her lake. The range of Tachanovsky's toadstool is limited to Yunin Lake in Peru.

All species during the nesting season live in closed water bodies, mainly on shallow lakes with a sandy bottom and without currents. Rarely, representatives of grebes can be found on slow-flowing rivers. Two species, the Magellanic grebe and the western grebe, sometimes nest in calm sea bays. In South America, some species have chosen exclusively high-alpine lakes of the Andes, where they nest at an altitude of up to 4000 m.

The only representative of the grebe, the great grebe or grebe, is found in artificial reservoirs in some areas; in Central Europe, she even mastered the ponds in city parks.

Only in the rest of the period, other than nesting, many species live on the sea. While the Magellanic grebe can be found several kilometers from the coast in the open sea, other species prefer to stay in the coastal zone.

Species living in the tropical and subtropical zones lead a sedentary lifestyle and fly exclusively to nearby seas. Types of the temperate climate zone - partly or completely migratory birds; outside the nesting season, they most often keep in large groups; for example, in the fall, about 20,000 individuals of the great grebe on Lake IJsselmeer (Dutch. IJsselmeer) or 750,000 individuals of the black-necked grebe on Mono Lake in California.

Grebes are primarily diurnal but can also be active at night when the full moon is bright. Many species are solitary birds, live in pairs during the nesting season; some of them live in groups during the winter.

Seven species: black-necked grebe, Australian griffon grebe, tadpole grebe, silver grebe, Tachanovsky's grebe, western grebe and Clark's grebe have a different lifestyle and nest in colonies.

As already mentioned, there are two main types of grebes: those that feed on fish and those that specialize in aquatic arthropods. The first type includes, for example, the great and western grebes, the second - the lesser and black-necked grebes. Specialization only means that fish or arthropods form the main diet of these species. Large species eat arthropods in addition to fish, while those that mainly prey on insects and small crustaceans supplement their diet with small fish.

Large species of grebes can swallow fish up to 20 cm long and up to 7.5 cm wide. Among the aquatic insects that smaller representatives of grebes feed on are larvae of dragonflies, mayflies, stoneflies, water bugs and water beetles. In addition, grebes eat aquatic snails, crustaceans, tadpoles, and adult frogs.

Often traces of aquatic plants can be found in the stomachs of grebes; the latter most likely get there by accident. Small toadstool stones are swallowed as gastroliths to grind food. Sometimes grebes swallow their own feathers, primarily from the chest or lower body. Swallowed feathers envelop indigestible food debris and are subsequently burped out in the form of lumps. Presumably, the toadstools do this to protect the stomach walls from damage that can be caused by the sharp bones of fish.

All grebes form monogamous pairs during nesting. Before the formation of a pair, a mating ritual takes place, which in some species, such as the Australian griffon grebe, can be simple, while in others it is quite complex. For phylogeneticists, a comparative analysis of the mating ritual of grebes is of particular interest. Smaller species, such as the lesser grebe and the lesser spotted grebe, as well as the larger species, the Magellanic grebe (which is however an exception), have a simple mating dance. In contrast, in most members of the genus Podiceps, as well as in the western grebe, stunningly spectacular, highly complex mating rituals can be observed. The synchronized movements during the marriage ceremony are accompanied by the perfected movements of the partners, which are very similar to a real dance. For example, in a large grebe, such a dance ends with the mutual offering of algae. And western grebes, after synchronously running through the water with outstretched necks, simultaneously dive into the water.

Mating in grebes takes place on land. After this, a period begins in which partners protect the territory of the future nest from representatives of both their own and other species, such as ducks. Aggressive behavior in the seven previously named species that nest in colonies is much less pronounced. These grebes can nest not only next to representatives of their own species, but also next to other birds. In Europe, such birds can be common gull and barnacle tern. In such mixed colonies, gulls and terns warn grebes in advance of approaching enemies.

From aquatic plants, branches and leaves, both partners build a floating nest, which is attached to some kind of vegetation, such as reed beds. On average, the diameter of the nest is 30 - 50 cm, in rare cases - up to one meter. Smaller species tend to build smaller nests, but nest size is also influenced by factors such as waves or the material used for construction.

Females lay from two to seven white, yellow or blue eggs, which after a while become covered with brown spots. Toadstool eggs are relatively small. The weight of one toadstool egg is about 3 - 6% of the weight of an adult bird. The absolute size of the eggs ranges from 3.4×2.3 cm (in the black-necked grebe) to 5.8×3.9 cm (in the western grebe). Small toadstools incubate up to three clutches per year, large ones - one or maximum two.

Incubation of eggs lasts about 20 - 30 days. Toadstools begin to incubate the clutch from the first egg. In order not to draw attention to their nest, many species approach it underwater. Both partners often leave the nest for several hours, but the embryos are extremely resistant to hypothermia. Before leaving the clutch, the birds cover it; the plants from which the nest is made rot and additionally heat the eggs from below. In addition, by covering the nest, grebes mask it from enemies.

Toadstool chicks hatch at different times, immediately climb onto the backs of their parents and hide there for some time. This gives adult birds the opportunity to incubate the rest of the eggs laid later. The female incubates the remaining eggs, while the male feeds the hatched chicks. The hatching of the chicks lasts only a few minutes, since a long stay in a humid environment is dangerous for the life of the chicks. Nestlings of all grebe species (except the western grebe and Clark's grebe) are distinguished by their typical striped plumage. These strips first pass through the whole body, later remain only on the throat and head. The chicks can swim and dive on their own from the very beginning after hatching. However, since they can't regulate their body temperature well enough and cool off quickly, chicks spend most of their time on their parents' backs. While one of the parents swims with the chicks on its back, the other is looking for food. Newly hatched chicks have a bare patch of skin on the crown of the head that turns red as a result of a rush of blood if the chick is under stress associated with hunger or (possibly) overheating. There is a misconception that grebes have pockets under their wings, in which the chicks find refuge when the adult birds dive underwater. An adult bird that transports chicks usually remains on the surface of the water and does not dive.

Depending on the species, young grebe chicks remain on the back of their parents for 44 to 79 days. Until the moment when the chicks leave the back, there are fights between them for food, in which the parents do not interfere. Such fights often result in deaths among the weaker chicks. The chance that a young grebe chick will survive the first twenty days is about 40 - 60%.

The order includes 6 modern genera and 20 species (2 species are extinct), one more species can be considered extinct with a high degree of probability. The Russian name "grebe" comes from the disgusting taste of their meat, which has an unpleasant smell of fish.

Sources

SQUAD PANCO-LIKE - PODICIPEDIFORMES

DIVING WITH PASSENGERS

Grebes are a small, well-defined order of birds, including a single family. For a long time, grebes were united with loons in one detachment. In classical systems, toadstools are still usually placed at the very beginning, immediately after loons. However, the proximity of loons and grebes is apparent, the similarity of their external appearance is due to convergence associated with adaptations to diving. Later, grebes began to be considered a relatively young group, leading from ancestors related to charadriiformes and crane-like birds. According to a classification based on DNA similarity, the grebe family is a member of a huge order of “storks”, which unites most aquatic and near-aquatic birds, as well as diurnal predators. Thus, the family ties of grebes remain unclear, in any case, this is a separate group of birds, deeply specialized for life in fresh water.

The first grebes (genus

neogaeornis) already known from the Upper Cretaceous of South America. They lived 80 million years ago in what is now Chile. modern genus Podiceps known from the Oligocene. Grebes are distributed everywhere except the Arctic, Antarctic and a number of oceanic islands: Species of the genus Poliocephalus- endemic to Australia and New Zealand, genus Rollandia- South rather kind Aechmophorus- North America. The center of the current diversity of grebes is South America, and judging by the fossil finds, it was probably also the center of origin of the group. In the Western Hemisphere, 5 out of 6 genera and 15 out of 22 modern species of grebes are represented. 5 species from 2 genera nest in Russia.FAMILY GREAT - PODICIPEDIDAE

A valky streamlined body, an elongated movable neck, a straight pointed beak, a schizognathic skull,

with short strong legs carried back, with a narrow pelvis, grebes resemble loons. However, they have a number of significant anatomical differences. Cervical vertebrae 17-21 (in loons 14-15); The last 3-4 thoracic vertebrae fuse into the dorsal bone (loons do not have a dorsal bone); the sternum is widened and short (in loons it is narrow and long), the patella is large and elongated (in loons it is small). Salt-excreting supraorbital glands in grebes are almost not developed, which indicates their “freshwater”, unlike loons, past. The muscles of the legs are very powerful, but do not have 9 of the full set of muscles characteristic of the loons. Only the tarsals with paws protrude from the common skin, the legs are located along the body and are pressed, their muscles are surrounded by the muscles of the body. The tarsus, like that of the loons, is flat, strongly compressed from the sides, but the structure of the fingers differs sharply from that of most waterfowl. Each of the three fingers pointingforward, bordered by an independent wide skin lobe and ends with a flat, blunt claw, similar to a nail. The inner edge of the blades is much wider than the outer one, which is important when diving. The hind toe is small, but also bordered by a leathery blade, the horizontal “foot” is practically absent.

Grebes are noticeably smaller than loons: the largest species is Magellanic grebe

(Podiceps gigas) has a body length of up to 77 cm and weighs up to 1.6 kg, small toadstools of the genus Tachybaptus (including our little grebe T. ruficollis)can weigh 100-150 g with a length of 21-25 cm.

Feeding almost exclusively on animal feed has caused distensibility of the esophagus and the absence of a goiter in grebes. The stomach is elongated, voluminous, but thin-walled, the cecum is small.

The plumage of grebes is dense, dense, water-repellent, with a silky sheen. The feathers have a small side stem. The apteria occupy a small area, the coccygeal gland is also feathered, but the bridle remains bare (in loons it is feathered). The total number of feathers can reach 20,000 or more. Tail feathers are reduced, primary fly feathers - 12, secondary - 17-22. The molting of all flywheels occurs simultaneously, accompanied by a loss of the ability to fly. The wings are narrow, but not short, the flight is fast, straightforward. The silhouette of a flying bird is characteristic: an elongated long and thin neck, an elongated body, behind the rear edge of which paws protrude instead of a missing tail. Toadstools cannot maneuver in the air and take off from land; they take off from the water after a long run.

The general type of coloration, especially in winter plumage, is standard for waterfowl - dark top, light bottom, there are exceptions in breeding plumage. Sexual dimorphism is poorly developed, seasonal, on the contrary, is significant. In nuptial attire, many species develop bright decorative feathers (tufts, collars) on the head, often the beak, neck, and sides acquire a bright color. A complete molt occurs at the end of summer - autumn, an incomplete prenuptial molt (affecting only part of the contour plumage) - at the end of winter - early spring. Tropical species have only one molt. Most grebes are characterized by a bright red (rarely yellow, white) iris. The legs are painted discreetly - in dark gray, greenish, brownish tones.

Brood-type chicks have a single downy outfit with characteristic longitudinal stripes on the body and neck, a complex contrasting pattern on the head and beak. In addition to variegated fluff, brightly colored (red, raspberry) areas of bare skin on the forehead, near the eyes, around the beak are involved in drawing up the pattern. The coloration of the head and neck of nestlings is species-specific and has an obvious signal value. So, a pale frontal plaque signals to parents that the chick needs to be heated. Only in kind

Aechmophorusdown jackets have a simple coloration, reminiscent of the winter outfit of adult birds.

The change from downy to chick feather outfit is stretched. The longitudinal pattern on the head and neck is often preserved until the molt in the first winter plumage at the end of autumn. Birds acquire the final adult outfit at the 2nd year of life, young small species - already next spring.

Due to the peculiarities of the structure, grebes swim and dive perfectly, feed effectively in the water column. The foot of the toadstool operates under water with a minimum expenditure of muscular energy in the individual phases of the stroke. When the foot moves forward, the metatarsus automatically turns inward along the longitudinal axis, cutting through the water with the edge of the blades of the fingers and not encountering strong water resistance. With a “working” stroke back, the metatarsus returns to its original state, the fingers “lean” on the water column with the blades and give the body a push forward. Amplitude

rotation of the metatarsus reaches 120 °.

The cruising speed of grebes under water reaches 3 m / s. Unlike loons, grebes do not use wings when diving. Usually they feed at a depth of 1-1.5 m, but sometimes they get into nets at depths up to 25 m. While feeding, the birds spend an average of about 30 seconds under water, but they can stay there for up to 3 minutes. Much less often, grebes catch prey on and above the water surface, picking insects from plants and even catching them in the air. The bird captures prey with the tip of a sharp beak; in the process of swallowing, the branches of the lower jaw are automatically parted to the sides. This adaptation (streptognathia) makes it possible to swallow large objects whole. Streptognathia is not developed in loons.

Grebes feed on aquatic insects, crustaceans, mollusks, tadpoles, and fish. Supplementary food (algae) is found only occasionally. The degree of fish-eating depends on the size of the species, season, geographical distribution. In the nesting period, invertebrates form the basis of nutrition; in wintering places, grebes become almost completely piscivorous. From the first day of life, the stomachs of chicks contain small covering feathers obtained from feeding from their parents. Feathers provide the formation of pellets from the chitin of invertebrates, bones and fish scales. When burping the pellets into the water, the birds collect the released feathers and eat them again.

Grebes seem to feed only during the day, and nocturnal activity is observed during the migration season and during the mating season. On migrations, they fly only at night, during the day they feed, rest. Migration is characteristic of species living in temperate latitudes of the northern and partly southern hemisphere. During migration and wintering, they are found mainly not in fresh water bodies, but in coastal waters of seas that do not freeze for the winter. Most tropical and alpine species and populations of grebes live settled in fresh inland waters, or make minor local migrations. At least 5 species inhabit the cold mountain lakes of the Andes in the puna belt at an altitude of 3000-5000 m above sea level

(height record apparently belongs to the silver grebe (Podiceps occipitalis). Settlement of some species, such as the Atitlan grebe (Podilymbus gigas) with lake Atitlan in Guatemala, short-winged grebe (Rolandia microplera) from the Andean lakes Titicaca and Poopo, Tachanovsky's grebes (Podiceps tacwnowskii) with lake Junin, also in the Andes, led to a significant reduction in their wings. These birds are practically unable to fly.

Grebes never form true flocks, although on migration and wintering aggregations of up to several hundred swimming birds can be seen. Usually grebes are found singly or in pairs. They are monogamous, pairing up for one season. Most species are characterized by nesting conservatism.

For nesting, grebes, as a rule, choose shallow fresh water bodies with stagnant or weakly flowing water, covered with dense emersed vegetation. Many species nest together, forming colonies of several dozen nests, often on the periphery of a gull colony or near coot nests. Neighborhood with rather aggressive species is a kind of protection of the nest from attacks of predators. Floating nests are characteristic, usually surrounded by stems of aquatic plants, but birds can also place them in open water. Sometimes the nests float freely, more often they touch the bottom with their base and are fixed in one place. Since grebes are almost unable to walk on land, they very rarely build nests on the shore, at the water's edge or on a hummock. Western grebe only

(Aechmophorus occidentalis) and Clark's toadstool (Ae. clarkii),living in the west of North America, walk well on land and can arrange nests at a considerable distance from the water.

Partners usually build several nests from a variety of plant material - stems, leaves, rhizomes. Only one nest is used for laying eggs, while the rest serve as resting and mating platforms. Like loons, grebes cannot mate on water. The mating ritual of toadstools is very complex and diverse. It is a characteristic pair dances on the water, consisting of several figures performed by birds synchronously. Partners dive; “run on water”, noisily slapping their paws; demonstrate ritual turns of the head, fluffing decorating feathers; they exchange shreds of aquatic plants that they hold in their beaks. The most typical is the “penguin pose”, when the birds stand on the water in a column; “cat pose” - the wings are half-open, the plumage is tousled, the feathers on the head are fluffy; “hunchback posture” - the head is lowered, the neck is bent, the feathers of the back are raised. There is also a group current, in the group the most initiative individual is usually singled out - the “instigator”. Ritual poses are accompanied by sound signals. Vocalization is diverse - whistling of different tonality, rumbling trills, screeching, nasal and guttural screams. In the mating season, grebes are noisy, at other times they are more silent. Ritual also comfortable behavior - cleaning plumage, touching the chest after diving.

In clutch from 2 to 10 oblong eggs. Freshly laid eggs have a matte white color, but gradually acquire a greenish-brown hue, stained with wet nest material. Incubation usually begins with the second egg and lasts 20-30 days. Both partners participate in incubation and care of the chicks. When leaving the nest for feeding, the bird covers the eggs with nesting material,

masking them, and possibly “warming up” with the heat released during the decay of vegetation. Chicks hatch at different times. In a clutch discovered only in 1974 in the south of Patagonia, a tadpole grebe (Podiceps gallardoi) only 2 eggs, from which only the first chick hatches. After hatching, the chicks climb onto the backs of their parents and they carry them on themselves for some time, and often feed them on their backs. In cold weather, the chicks literally burrow into the feathers of adults. Sometimes grebes even dive with chicks under their wings. Gradually, down jackets increasingly go into the water, learn to dive, try to collect food themselves. Feeding lasts 44-79 days, then young birds become independent, broods break up. Ontogeny in small species is faster. Some populations of low latitudes have second and even third clutches during the summer. Birds reach sexual maturity by the beginning of the 2nd (large species - 3rd) year of life. The longevity record (13 years) belongs to the little grebe. Toadstools do not tolerate captivity well, but in semi-free conditions they can form pairs and breed. There are no intergeneric hybrids in grebes; there is limited (and sometimes absorbing) crossing between some closely related species.

There are few natural enemies in adult grebes, since the birds spend most of their lives afloat and immediately dive in case of danger. They are more vulnerable in flight. Toadstool clutches are devastated by many feathered and four-legged predators, in the European part of Russia these are primarily large gulls, gray crows, marsh harriers, foxes and raccoon dogs. The negative impact of predators is exacerbated by human anxiety. To an even greater extent, clutches suffer from sudden rises in the water level, which floods the nests. Toadstool eggs can only tolerate short-term flooding.

. Sometimes up to half of the clutches die from the combination of these factors. Chicks are often prey for large fish.

On wintering, cases of mass death of grebes were noted during the period of sharp cold snaps, when usually non-freezing water bodies are covered with ice. Toadstools suffer from winter storms, oil pollution of water. In modern conditions, grebes have become important as a biological indicator of the degree of pollution of fresh water bodies with pesticides and heavy metals. As fairly large and completely aquatic predators, they are the last link that accumulates harmful chemical compounds in the ecological chains of inland waters.

Settling on fish farms, some grebes can be considered conditionally harmful, although the basis of their diet in most places is aquatic invertebrates. As special studies have shown, the juveniles they eat make up tenths of a percent of the total number of fish in a particular reservoir, so the harm of grebes is greatly exaggerated. During the winter they feed

predominantly small non-commercial fish species - small herring, sculpins, sticklebacks, blennies, etc.

Until the beginning of the 20th century. grebes were intensively exterminated in Europe because of the demand for downy skins - the so-called "bird fur". At present, it is of commercial importance due to the poor quality of meat, although everywhere they are hunted little by little along with ducks and coots. The origin of the Russian name “grebes” is probably also associated with the inedibility of their fish-smelling meat, but perhaps the characteristic silhouette of birds on the water was meant:

a thin long neck and a disproportionately large head due to a feather collar resembled a thin-legged toadstool mushroom. It's funny that the English name of the bird is"Grebe" sounds like a “mushroom”, which is very similar to the Russian name.

Thanks to their fame as excellent divers, grebes have become characters in the folklore and mythology of many peoples. In the north of Siberia and in some regions of Canada, there is a legend that it was the grebe, diving deep, that raised from the bottom of the sea that covered the whole world, a piece of land that became mainland land.

Most grebes are still fairly common, but 3 narrow range species are endangered and 2 are probably extinct by now. In the middle of the XX century. Tachanovsky's flightless grebe was a massive species on the lake. Junin in the Andes, but after the construction of an enrichment plant and the subsequent pollution of the lake, its numbers began to decline rapidly. By the end of the 70s. only 100 pairs have nested, by now only 40 pairs remain. Now the lake has been declared a reserve, pollution has been stopped, but it is supposed to supply Lima, the capital of Peru, with fresh water from this lake, which is likely to lead to fluctuations in water levels, and therefore to a deterioration in nesting conditions for birds.

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A whole range of reasons led to the death of the Atitlan grebe, an endemic of the volcanic lake. Atitlan in the mountains of Guatemala at an altitude of 1700 m. In 1929 on a lake with an area of ​​130 km

2 about 400 individuals of this large flightless bird lived. The catastrophic decline in numbers is associated with the introduction of the predatory North American perch into the lake. (Micropterus), destroying broods. Thanks to conservation measures, the number of the species briefly increased from 86 birds in 1966 to 232 in 1975; reduction in the species population. At the same time, the recreational load on the shores of the lake increased several times. The final extinction of the Atitlan grebe was caused by competition (and perhaps even absorptive crossing) with a very close, but twice as small and flying, species - the variegated grebe (Podilymbus podiceps). This species, widespread in the western hemisphere, settled on the lake. Atitlan in recent decades has begun to displace the endemic. By 1985, 55 individuals remained with the Atitlan grebe phenotype, now the species has probably completely disappeared.

Since the late 1980s there is no information about the Andean grebe

(Podiceps andinus)from the lake Tota, located in the mountains of Central Colombia at an altitude of 3000 m. Release of rainbow trout into the lake (Saimo gairdneri) led to a drop in the number of birds from 300 individuals in 1968 to 3 in 1977.

Adsorptive hybridization with a closely related species (little grebe) may lead to extinction of the pygmy grebe

(Tachybaptus rufolavatus) - endemic lake. Aloatra in northern Madagascar. The little grebe invaded the waters of the island from Africa following the introduced tilapia (Tilapia), the fry of which serve as food for the grebe. By the 1990s there are no more than 20 pairs of pygmy grebe left. A more common species on the island, the Madagascar grebe, also suffers from hybridization with a small grebe. (T. pelzelnii).

At present, in most regions of Russia, grebes are increasing in numbers and expanding their range, actively populating the ponds of fish farms, but in some places they are rare, distributed sporadically. Lesser, red-necked, grey-cheeked grebes are included in the Red Book of the Moscow Region.