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JOrnitho

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Отправлено: 01.05.22 18:53. Заголовок: Fauna of Europe

I found some other descriptions in the files of my pc, this time for European animals. These two are of two species of geese.

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Western diving goose (Brantamergus occidentalis)
During the Holocene, humans interfered with nature through several ways. While some local species suffered and had their populations reduced, others were introduced to many other continents. Sometimes, the local and introduced species were close enough to each other, being part of the same Genus. In these cases, they could reproduce with each other, giving origin to hybrids that would share the genes of both species.
The western diving goose is an example of species that originated under these conditions. These birds originated from Western Europe and are the result of the long time hybridization between the barnacle goose (Branta leucopsis) and the Canadian goose (Branta canadensis), which was introduced in European lands by the humans.
This species spends the summer in the coastal and estuarine areas of Scandinavia and in islands of the Barents Sea and Kara Sea. During the winter, these birds migrate in large flocks to the Bay of Biscaya.
They are small and compact birds, with a short neck. Both male and female have 54 cm of length and a wingspan of 87 cm. They have a black neck with a white "chinstrap", while their head has a black strip crossing their eyes and joining the black of the neck. The top of the head is white. They also have grayish brown backs and wings, silver-gray rump, black tail feathers. Its belly is white, while the chest is pale gray. Adults also have a white neck ring at the base of the neck. The beak, legs and feet are dark gray. The main characteristic of this species are their large webbed feet, which they use to swim underwater. Due to that, these birds are slow and clumsy when moving on land.
The western diving goose feeds on algae, crustaceans, molluscs and sometimes small fish that it catches by diving underwater. While doing it, these birds only use their large feet for propulsion. This adaptation allows these birds to avoid competition with the larger species of goose that feed on land, such as Hemiswans and the Gainsboro geese.
During the second year of their lives, western diving geese find a mate. They are monogamous, and most couples stay together all of their lives. If one dies, the other may find a new mate. The female lays from two to nine eggs, and both parents protect the nest while the eggs incubate, but the female spends more time at the nest than the male.
The nest is frequently built high on mountain cliffs close to the sea and away from predators. Like all geese, the goslings are not fed by the adults. Instead of bringing food to the newly hatched goslings, the parents show them the way to jump from the cliff and the goslings follow them by instinct and take the plunge. Unable to fly, the goslings jump off the cliff and fall. However, their small size, feathery down, and very light weight helps to protect some of them from serious injury when they hit the rocks below, but many die from the impact. While some families still need to do a clumsy walk toward the water, others are lucky enough to have nests so close to the sea that the goslings fall directly on the water.
The goslings enter the fledgling stage with 8 weeks of age. They do not leave their parents until after the spring migration, when they return to their birthplace. The sexual maturity of this species is reached when they have two years and the lifespan is of 27 years.
The western diving goose has a subspecies called American diving goose (B. o. americana), which nests in Greenland and in areas close to the Baffin and Labrador Sea. During winter, they migrate to the Gulf of Mexico. The plumage between the two is similar, but the American one is smaller.
The eastern diving goose (Brantamergus leucocephalus) is another representative of the Genus Brantamergus. With 50 cm of length and 83 cm of wingspan, this species is the smallest of the Genus. Their plumage is similar to that of its western counterpart, with the exception of the head that is totally white. This species nests on the islands in the seas of Okhotsk and Bering, with their largest colony being located in the cliffs of the Kuril Islands. During winter, they migrate to the coastal areas of the East China Sea.

Steppe goose (Geochen migratorius)
During the Holocene, humans introduced many species to other continents. With their extinction, some of these creatures continued to thrive, giving rise to new genera. The steppe goose of the Genus Geochen is a representative of this situation. This bird is a descendant of the Egyptian goose (Alopochen aegyptiaca) who had been introduced by humans to Western Europe. This species evolved to live in forested steppes and grassland of Europe, with the easternmost part of its range being North of the Fourseas. During winter, this species migrates to the savannas of Africa and Zinj Land. This species only forms flocks when they are in their wintering areas. While breeding, the pairs will not tolerate the presence of others of the same species.
The steppe goose has 64 cm of length and 110 cm of wingspan. This species is highly dysmorphic, with the males being slightly larger than the females. The plumage between the two is also different. The males have a black neck and head, with a bright auburn circle around their eyes. Their chest is chestnut and their body is white. The wing coverts are black, the primary are dark grey, and the secondaries green and chestnut. The females have a pale gray neck and head, with a brownish-red circle around their eyes. Like the males, they also have a chestnut chest and white body, but their wing coverts are pale gray, with the primary and secondaries being brown.
Both male and female of this species have a serrated beak, which allows them to crush their food and catch small animals. Both the beak, legs and feet are red. Their legs are longer than that of their ancestors, which allows them to run swiftly through the grassland. During its evolution, the web present on the feet of the steppe goose became greatly reduced. This was an adaptation for the terrestrial lifestyle that this species adopted. Even then, they will occasionally appear in shallow freshwater reservoirs to eat molluscs, plants and crustaceans. However, they swim poorly, only staying in places where the water doesn't cover their legs.
With the exception of the occasional aquatic food that they eat, most of the steppe goose's diet comes from things that they can find in the grasslands and steppes. They eat seeds, leaves, grasses and plant stems. However, they have preference for locusts, worms, or other invertebrates, which increases during the nesting season.
This species is monogamous, with pairs staying together even during the migration. Usually, their nests are built on hollowed trees, rock crevices and empty nests of other birds that are high enough from the ground. It forces the goslings to jump down from there. However, some will also build nests in the ground, hidden among the vegetation. During the breeding season, these birds are very aggressive, not tolerating individuals of the same species to make nests near them. Predators that approach the nest are attacked mercilessly, including birds of prey. In these cases, the female will distract them by flying while the male targets their wings, seeking to make them fall off the sky. Even peaceful herbivores that decide to graze near the nest will be attacked. Individuals that make nests in the ground are more agressive.
The female lays eight eggs in a nest made of reeds, leaves and grass and both parents take turns incubating them. The incubation period lasts for 33 days with only the female looking after the nest, the male remains near the nest, protecting it against predators. The goslings leave the nest immediately after hatch The fledging period for the downy young lasts on average eight weeks. The young remain with the parents during the migration, but once arriving on their wintering grounds they leave them.