The red-crowned crane (Grus japonensis), also called the Japanese crane is a large east Asian crane and among the rarest cranes in the world. In some parts of its range, it is known as a symbol of luck, longevity and fidelity. Adult red-crowned cranes are named for a patch of red bare skin on the crown, which becomes brighter in the mating season. Overall, they are snow white in color with black on the wing secondaries, which can appear almost like a black tail when the birds are standing, but the real tail feathers are actually white. Males are black on the cheeks, throat and neck, while females are pearly gray in these spots. The bill is olive green to greenish horn, the legs are slaty to grayish black, and the iris is dark brown.
This species is among the largest cranes, typically measuring about 150 to 158 cm (4 ft 11 in to 5 ft 2 in) tall and 120–150 cm (3 ft 11 in–4 ft 11 in) in length (from bill to tail tip). Across the large wingspan, the red-crowned crane measures 220–250 cm (7 ft 3 in–8 ft 2 in). Typical body weight can range from 7 to 10.5 kg (15 to 23 lb), with males being slightly larger and heavier than females and weight ranging higher just prior to migration. On average, it is the heaviest crane species, although both the Sarus and Wattled Crane can grow taller and exceed this species in linear measurements. The maximum known weight of the red-crowned crane is 15 kg (33 lb). Among standard measurements, the wing chord measures 56–67 cm (22–26 in), the exposed culmen measures 13.5–16.7 cm (5.3–6.6 in) and the tarsus measures 25.5–30.1 cm (10.0–11.9 in).
In the spring and summer, the migratory populations of the red-crowned crane breed in Siberia (eastern Russia), northeastern China and occasionally in northeastern Mongolia] (i.e., Mongol Daguur Strictly Protected Area). The breeding range centers in Lake Khanka, on the border of China and Russia. Normally the crane lays 2 eggs, with only one surviving. Later, in the fall, they migrate in flocks to Korea and east-central China to spend the winter. Vagrants have also been recorded in Taiwan. In addition to the migratory populations, a resident population is found in eastern Hokkaidō in Japan. This species nests in wetlands and rivers. In the wintering range, their habitat is comprised mainly by paddy fields, grassy tidal flats, and mudflats. In the flats, the birds feed on aquatic invertebrates and, in cold, snowy conditions, the birds switch to mainly living on rice gleanings from the paddy fields.
Red-crowned cranes have a highly omnivorous diet, though the dietary preferences have not been fully studied. They eat rice, parsley, water plants, carrots, reed buds, acorns, buckwheat and a variety of water plants. The animal matter in their diet consists of fish, including carp and goldfish, amphibians, especially salamanders, snails, crabs, dragonflies, small reptiles and other birds, especially waterfowl. They seem to prefer animal food matter throughout the year, although rice is now essential to survival for wintering birds in Japan and grass seeds are an important food source. While all cranes are ominivorous, per Johnsgard, the two most common crane species today (the Sandhill and Common Cranes) are amongst the most herbivorous species while the two rarest species (the red-crowned and Whooping Cranes) are perhaps the most carnivorous species.
They typically forage by keeping the head close to the ground, jabbing the bill into mud when something edible is encountered. When capturing fish or other slippery prey, they may quickly jab in a similar fashion to a heron. Although animal prey can be swallowed whole, usually red-crowned cranes more often tears up prey by grasping with its bill and shaking it vigorously, eating pieces as they fall apart. Most foraging occurs in wet grasslands, cultivated fields, in shallow rivers or on lakeshores.
The population of red-crowned cranes in Japan is essentially non-migratory, with the race in Hokkaido moving only 150 km (93 mi) to its wintering grounds. Only the mainland population experiences a long-distance migration. They leave their wintering grounds in spring by February and are established on territories by April. In fall, they leave their breeding territories in October and November, with the migration fully over by mid-December.
Flock sizes are affected by the small numbers of the red-crowned crane and, given their largely carnivorous diet; some feeding dispersal is needed in natural conditions.
Wintering cranes have been observed foraging, variously, in family groups, pairs and singly, although all roosting is in larger groups (up to 80 individuals) with unrelated cranes. By the early spring, pairs begin to spend more time together, with non-breeding birds and juveniles dispersing separately.
It is believed that breeding maturity is reached at three or four years of age. All mating and egg-laying is largely restricted to April and early May. A red-crowned crane pair will duet in various situations, helping to establish formation and maintenance of the pair bond, as well as territorial advertisement and agonistic signaling. The pair move rhythmically until they are standing close, throw their heads back and let out a fluting call in unison, often triggering other pairs to start duetting as well. As it is occurs year around, the social implications of dancing are complex in meaning. However, dancing behavior is generally thought to show excitement in the species.
Nesting territories range from 1 to 7 km (0.62 to 4.35 mi) and are often the same year after year. Most nesting territories are characterized by flat terrain, access to wetland habitat and tall grasses. Nest sites are selected by females but built by both sexes and are frequently in a small clearing made by the cranes. A majority of nests contain two eggs, though 1 to 3 have been recorded. Both sexes incubate the eggs for at least 30 days. They also both feed the young when they hatch. Staying in the nest for the first few weeks, the young start to follow their parents as they forage in marshes by around 3 months of age. By early fall, the young are fledged and are assured fliers by migration time. Although they can fly well, crane young remain together with their parents for around 9 months. The average adult lifespan is around 30 to 40 years, with some specimens living to 70 years of age in captivity. It is one of the longest living species of bird.
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