Crane
The flying crane stretches its neck and legs with a graceful and smooth posture. Cranes are excellent high-altitude fliers. Gray cranes (pictured) fly at an altitude of more than 9,000 meters as they migrate across the Himalayas - equivalent to the altitude of a jetliner.
Cranes are the best of birds. Not only is it one of the oldest communities, its origins can be traced back to the Paleocene Epoch about 60 million years ago; it also has a long lifespan, and artificially raised cranes can live for seventy or eighty years. At the same time, cranes are also the tallest flying birds, with some species standing up to 1.8 meters.
Crane is famous for its elegance and elegance. For a long time, many local people have been in awe of cranes. But unfortunately, cranes have become one of the most endangered birds in the world, with 9 out of 15 species currently under threat. Humans are undoubtedly responsible for their decline in recent years.
Long neck, long legs and
Reproduction Biology
Most wild cranes do not start breeding until they are 3 to 5 years old. Those species that are easy to survive, such as sandhill cranes and gray cranes, usually raise two offspring per breeding. On the contrary, those rare species, including whooping crane and white crane , often only raise one chick, and artificial breeding is no exception. They are often more difficult to breed than more likely to survive.
is a single configuration. As spring or the rainy season approaches, pairs retreat to remote meadows or wetlands where they establish and maintain their own breeding territories. May be thousands of hectares in size, depending on species and terrain.
Pairs of mates will sing in unison duet . The individual calls of the male and female birds are clearly distinguishable and consistent at the same time. In most species, the male sings a series of long, low calls, followed by several short, high-pitched calls by the female. The sex of the bird can be distinguished from this show-off behavior. And this kind of "Qingming" helps to consolidate the relationship between spouses and promote the maintenance of the reproductive field. However, as the relationship between the two cranes stabilizes, this chorus becomes more of a demonstration. At dawn, pairs of couples begin to sing in unison to indicate the scope of their respective territories. Neighboring couples responded with more choruses, and the chorus echoed over the wetlands and grasslands within thousands of meters.
In a pair of couples with a stable relationship, the reproductive status of both parties is kept in sync through the regulation of hormonal cycles. Hormone cycles are affected by factors such as weather, day length, and complex show-off behaviors such as "singles" and "wedding dances." Cranes begin mating weeks before laying eggs. To ensure reproductive success, the female bird must be fertilized within 2 to 6 days before laying eggs.
The mate will build a platform nest somewhere out of the way within the wetland breeding territory. Crowned cranes usually lay 3 eggs in a clutch, while other cranes generally lay 2 eggs, with the exception of wattled cranes, which in most cases only lay 1 egg.
The male and female cranes share the task of incubation. Female cranes are generally responsible for incubating eggs at night, while male cranes take over during the day. The crane that is not in the nest usually forages far away from the nest, sometimes in a "neutral zone" with other cranes. The incubation period is 28 to 36 days, depending on the species and the energy invested by the parent bird. Crowned cranes always wait until a clutch of eggs is laid before they hatch, so the chicks hatch at the same time. Other types of cranes begin hatching after the first egg is laid, and the chicks are generally born 2 days apart.
Crane chicks are well developed as soon as they hatch (that is, they are precocious) and follow their parents around in shallow waters. They grow all their flight feathers after 2 to 4 months. The chicks of larger tropical species such as Wattled Crane and Red-necked Crane have a longer period of growing flight feathers, while the white crane has a shorter period - because the climate close to the Arctic makes food abundant. Becoming very short, the chick must develop rapidly during this time. Although crane eggs hatch in most cases, many chicks die, and many species listed as endangered can only raise one offspring at a time. After the chicks can fly, they still live with their parents until the next breeding season. In some species, newly grown cranes will follow their parents southward to traditional wintering grounds thousands of kilometers away to familiarize themselves with migration routes.
The relationship between nature and nurture is well reflected in the crane. Although their complex visual and auditory showoffs are based on an innate instinct, it is acquired learning that determines the context in which the showoff occurs. For example, baby cranes raised by humans prefer to associate with humans rather than cranes, and they may seduce or threaten humans. In addition, the parent bird will teach the young crane where to find food and what kind of food to find.
Threats to Survival Protection and Environment
Cranes that feed on aquatic animals face the most severe threats to their survival. A key reason for their decline is the degradation and disappearance of wetlands. In addition, their large size and eye-catching plumage make them easily spotted by hunters and egg snatchers.
Whooping cranes in North America are considered the rarest species of cranes. In the early 1940s, there were only about 20 left, and today there are only about 400 (including wild and captive ones). Followed by red-crowned crane , there are about 1,800 wild ones. There are about 2,500 to 3,000 white cranes, about 5,000 white-naped cranes and black-necked cranes each, 8,000 wattled cranes, and 11,000 white-headed cranes. Fortunately, cranes are beloved birds after all, and many Asian countries have made efforts in recent years to protect wetlands that are crucial to their survival. However, the killing of cranes continues in countries such as Afghanistan and Pakistan. In the northwest border region of Pakistan, 2,000 to 4,000 live cranes are killed every year. As the population in wetlands soars, the ecological pressure on wetlands is increasing day by day.
There are 5 endangered species in Asia, with only a few thousand of each species. But because cranes hold special symbolic significance in the cultures of many Asian countries, conservationists are optimistic about avoiding the extinction of these species despite their small numbers. Only the Siberian Crane, which is highly dependent on wetlands, may become an exception. Siberian cranes only dig fleshy roots and tubers from aquatic plants in shallow waters, unlike other species that can forage in farmlands and grasslands during migration and wintering grounds. In China, protecting large areas of shallow wetlands is undoubtedly a major challenge, because more than half of the Siberian Cranes live here from October to April of the following year.
In Africa, although the four regional cranes are abundant in the local area, they have experienced a large-scale decrease in recent years due to human intervention. Among the 18,000 blue cranes in the world, except for about 100 in Namibia, they are all concentrated in South Africa. However, in Namibia, the conversion of grasslands into forests, large-scale farm subdivisions, and poisoning are seriously threatening the blue crane, the country's national bird, and the local populations of wattled cranes and gray-crowned cranes are also under threat. In West Africa, the survival of black-crowned crane is also threatened by habitat loss, being rounded up by humans and used for trade. But from a global perspective, from East Africa to South Africa, the situation of gray crowned cranes is relatively reassuring. However, overgrazing of wetlands and extensive human interference have caused the species to decline in many areas.
Like the Asian white crane, the African wattled crane is also wetland dependent. Fortunately, there are several large wetlands in central Africa (especially the Okavango Delta in Botswana, the Kafue Flats and Bawelu Marshes in Zambia, and the Zambezi Delta in Mozambique). It houses a considerable number of Wattled Cranes. The water conservancy projects related to damming and the resulting changes in wetlands have become the biggest threat to the survival of the wattled crane.
