Red-crowned crane

Appearance

Adult red-crowned cranes are named for a patch of red bare skin on the crown, which becomes brighter during 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 slate to grayish black, and the iris is dark brown.

This species is among the largest and heaviest cranes, typically measuring about 150 to 158 cm tall and 101.2–150 cm in length . Across the large wingspan, the red-crowned crane measures 220–250 cm . Typical body weight can range from 4.8 to 10.5 kg , 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. On average, adult males from Hokkaidō weighed around 8.2 kg and adult females there averaged around 7.3 kg , while a Russian study found males averaged 10 kg and females averaged 8.6 kg ; in some cases, females could outweigh their mates despite the males' slightly larger average body weight. Another study found the average weight of the species to be 8.9 kg . The maximum known weight of the red-crowned crane is 15 kg . Among standard measurements, the wing chord measures 50.2–74 cm , the exposed culmen measures 13.5–17.7 cm , tail length is 21.5–30 cm , and the tarsus measures 23.7–31.9 cm .

Naming

The red-crowned crane is a big-sized bird and there are no natural predators within their wintering ground. With their height averaging 1.5 m , their large size deters most predators. As a result, red-crowned cranes often react indifferently to the presence of other birds such as small raptors; with harriers, falcons, owls, and usually buzzards being allowed to hunt small prey near a crane nest without any of these parties harassing each other. However, birds more likely to be egg or nest predators, such as corvids, some buzzards, and various eagles, are treated aggressively and are threatened until they leave the crane's territory. Mammalian carnivores, including red foxes, badgers, raccoon dogs, martens, and domestic dogs which pose a threat to eggs and chicks, are attacked immediately, with the parent cranes attempting to jab them in the flanks until the predators leave the vicinitly. These small predator do not present any danger to chicks in the presence of adults and are chased away by the crane without difficulty. Larger predator such as gray wolves and large dogs can be repelled by aggressive crane pairs. Occasionally, losses at the nest occur to some of the above predators. Introduced American mink on Hokkaidō are one of the most successful predators of eggs and nestlings. Also, immature and unwary subadult or even adult cranes may be ambushed killed by red foxes in Japan and leopard cats in South Korea, though this is rare reports, especially with adults. ...hieroglyph snipped......hieroglyph snipped... More often, these birds can easily defend themselves by using sharp beak or just fly away from danger....hieroglyph snipped...

Smaller white-naped cranes often nest near red-crowned cranes, but competition between these species for food in a common nesting area is lessened due to the greater portion of vegetation in the white-naped crane's diet. In cases where interactions turn aggressive between white-naped and red-crowned cranes, red-crowned cranes are dominant, as expected due to their considerably larger size. As reported researchers trying to band or examine the cranes or their nest, this powerful species is considered mildly hazardous and prone to respond quickly with considerable aggression to being approached or handled by humans and are able to inflict painful injuries using both its kicking feet and dagger-like beak.

Status

The population of red-crowned cranes is split into a migratory continental population in Korea, China, Mongolia, and Russia, and a resident Japanese population in Hokkaidō. The estimated total population of the species is only 1,830 in the wild, including about 950 birds in the resident Japanese population. Of the migratory populations, about 400-500 winter in China , and the remaining 1000-1050 winter in Korea. It received endangered status on 2 June 1970.

The National Aviary in Pittsburgh, Pennsylvania, ran a program where U.S. zoos donated eggs which were flown to Russia and raised in the Khinganski Nature Reserve and released into the wild. This program sent 150 eggs between 1995 and 2005. The program has been put on hold to concentrate on different crane conservation programs in Russia, such as education and fire suppression. Several hundred red-crowned cranes are kept in zoos around the world. Assuredly, the international efforts of Russia, China, Japan, and Korea are needed to keep the species from extinction. The most pressing threat is habitat destruction, with a general lack of remaining pristine wetland habitats for the species to nest. In Japan, little proper nesting habitat remains and the local breeding population is close to the saturation point.

In South Korea, it has been designated natural monument 202 and a first-class endangered species.

Behavior

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 with unrelated cranes. By the early spring, pairs begin to spend more time together, with nonbreeding birds and juveniles dispersing separately. Even while not nesting, red-crowned cranes tend to be aggressive towards conspecifics and maintain a minimum distance of 2 to 3 m to keep out of pecking range of other cranes while roosting nocturnally during winter. In circumstances where a crane violates these boundaries, it may be violently attacked.

Habitat

In the spring and summer, the migratory populations of the red-crowned crane breed in Siberia , north-eastern China and occasionally in north-eastern Mongolia . The breeding range centers in Lake Khanka, on the border of China and Russia. Normally, the crane lays two eggs, with only one surviving. Later, in the fall, they migrate in flocks to the Korean Peninsula 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, Japan. This species nests in wetlands, marshes 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.

Reproduction

Breeding maturity is thought to be reached at 3–4 years of age. All mating and egg-laying is largely restricted to April and early May. A red-crowned crane pair duets in various situations, helping to establish formation and maintenance of the pair bond, as well as territorial advertisement and agonistic signaling. The pair moves rhythmically until they are standing close, throwing their heads back and letting 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. To strengthen the bond, red-crowned cranes engage in dual honking rituals before performing a dance.


Pairs are territorial during the breeding season. Nesting territories range from 1 to 7 km2 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, either on wet ground or shallow water over waters no more than 20 to 50 cm deep. Sometimes, nests are built on the frozen surface of water, as frigid temperatures may persist well into nesting season. Nest building takes about a week. A majority of nests contains two eggs, though one to three 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. New hatchlings weigh about 150 g and are covered in yellow natal down for two weeks. By early fall, about 95 days after hatching, 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. Young cranes maintain a higher-pitched voice that may serve to distinguish them from outwardly similar mature birds, this stage lasting until the leave parental care. The average adult lifespan is around 30 to 40 years, with some specimens living to 75 years of age in captivity. It is one of the longest-living species of bird.

Food

Red-crowned cranes have a highly omnivorous diet, though the dietary preferences have not been fully studied. They eat rice, parsley, carrots, redbuds, 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, shrimp, small mammals like rodents and small birds like ducklings. They seem to prefer a carnivorous diet, although rice is now essential to survival for wintering birds in Japan and grass seeds are another important food source. While all cranes are omnivorous, per Johnsgard, the two most common crane species today are among the most herbivorous species while the two rarest species are perhaps the most carnivorous species. When feeding on plants, red-crowned cranes exhibit a preference for plants with a high content of crude protein and low content of crude fiber.

They typically forage by keeping their heads close to the ground, jabbing their beaks into mud when they encounter something edible. When capturing fish or other slippery prey, they strike rapidly by extending their necks outward, a feeding style similar to that of the heron. Although animal prey can be swallowed whole, red-crowned cranes more often tear up prey by grasping with their beaks and shaking it vigorously, eating pieces as they fall apart. Most foraging occurs in wet grasslands, cultivated fields, shallow rivers, or on the shores of lakes.

Migration

The population of red-crowned cranes in Japan is mostly non-migratory, with the race in Hokkaidō moving only 150 km 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.