Sandhill crane facts for kids
Quick facts for kidsSandhill crane
|Adult (behind) and juvenile|
The sandhill crane (Antigone canadensis) is a species of large crane of North America and extreme northeastern Siberia. The common name of this bird refers to habitat like that at the Platte River, on the edge of Nebraska's Sandhills on the American Plains. This is the most important stopover area for the nominotypical subspecies, the lesser sandhill crane (Antigone canadensis canadensis), with up to 450,000 of these birds migrating through annually.
The sandhill crane was formerly placed in the genus Grus, but a molecular phylogenetic study published in 2010 found that the genus, as then defined, was polyphyletic. In the resulting rearrangement to create monophyletic genera, four species, including the sandhill crane, were placed in the resurrected genus Antigone that had originally been erected by the German naturalist Ludwig Reichenbach in 1853. The specific epithet canadensis is the modern Latin word for "Canadian".
Adults are gray overall; during breeding, their plumage is usually much worn and stained, particularly in the migratory populations, and looks nearly ochre. The average weight of the larger males is 4.57 kg (10.1 lb), while the average weight of females is 4.02 kg (8.9 lb), with a range of 2.7 to 6.7 kg (6.0 to 14.8 lb) across the subspecies. Sandhill cranes have red foreheads, white cheeks, and long, dark, pointed bills. In flight, their long, dark legs trail behind, and their long necks keep straight. Immature birds have reddish-brown upperparts and gray underparts. The sexes look alike. Sizes vary among the different subspecies; the average height of these birds is around 80 to 136 cm (2 ft 7 in to 4 ft 6 in). Their wing chords are typically 41.8–60 cm (16.5–23.6 in), tails are 10–26.4 cm (3.9–10.4 in), the exposed culmens are 6.9–16 cm (2.7–6.3 in) long, and the tarsi measure 15.5–26.6 cm (6.1–10.5 in).
These cranes frequently give a loud, trumpeting call that suggests a rolled "r" in the throat, and they can be heard from a long distance. Mated pairs of cranes engage in "unison calling". The cranes stand close together, calling in a synchronized and complex duet. The female makes two calls for every one from the male.
Sandhill cranes' large wingspans, typically 1.65 to 2.30 m (5 ft 5 in to 7 ft 7 in), make them very skilled soaring birds, similar in style to hawks and eagles. Using thermals to obtain lift, they can stay aloft for many hours, requiring only occasional flapping of their wings, thus expending little energy. Migratory flocks contain hundreds of birds, and can create clear outlines of the normally invisible rising columns of air (thermals) they ride.
Sandhill cranes fly south for the winter. In their wintering areas, they form flocks over 10,000. One place this happens is at Bosque del Apache National Wildlife Refuge, 100 mi (160 km) south of Albuquerque, New Mexico. An annual Sandhill Crane Festival is held there in November.
Sandhill cranes are fairly social birds that usually live in pairs or family groups through the year. During migration and winter, unrelated cranes come together to form "survival groups" that forage and roost together. Such groups often congregate at migration and winter sites, sometimes in the thousands.
Sandhill cranes are mainly herbivorous, but eat various types of food, depending on availability. They often feed with their bills down to the ground as they root around for seeds and other foods, in shallow wetlands with vegetation or various upland habitats. Cranes readily eat cultivated foods such as corn, wheat, cottonseed, and sorghum. Waste corn is useful to cranes preparing for migration, providing them with nutrients for the long journey. Among northern races of sandhill cranes, the diet is most varied, especially among breeding birds. They variously feed on berries, small mammals, insects, snails, reptiles, and amphibians.
Sandhill cranes raise one brood per year. In nonmigratory populations, laying begins between December and August. In migratory populations, laying usually begins in April or May. Both members of a breeding pair build the nest using plant material from the surrounding area. Nest sites are usually marshes, bogs, or swales, though occasionally on dry land. Females lay one to three (usually two) oval, dull brown eggs with reddish markings. Both parents incubate the eggs for about 30 days. The chicks are precocial; they hatch covered in down, with their eyes open, and able to leave the nest within a day. The parents brood the chicks for up to three weeks after hatching, feeding them intensively for the first few weeks, then gradually less frequently until they reach independence at 9 to 10 months old.
The chicks remain with their parents until one to two months before the parents lay the next clutch of eggs the following year, remaining with them 10–12 months. After leaving their parents, the chicks form nomadic flocks with other juveniles and nonbreeders. They remain in these flocks until they form breeding pairs at between two and seven years old.
As a conspicuous ground-dwelling species, sandhill cranes are at risk from predators, which are probably the main nonanthropogenic source of mortality. Mammals such as foxes, raccoons, coyotes, wolves, cougars, bobcats, and lynx hunt them given any opportunity, the first three mainly hunting large numbers of young cranes, the latter four types more rarely taking full-grown cranes in ambush excepting the prolific bobcat. Corvids, such as ravens and crows, gulls, and smaller raptors such as hawks (largely northern harriers or red-tailed hawks) feed on young cranes and eggs. Cranes of all ages are hunted by both North American species of eagles. Mainly chicks and possibly a few adults may be preyed on by great horned owls and even the much smaller peregrine falcons has successfully killed a 3.1 kg (6.8 lb) adult sandhill crane in a stoop. In Oregon and California, the most serious predators of flighted juveniles and adults has been cited as golden eagles and bobcats, the most serious predators of chicks are reportedly coyotes, ravens, raccoons, American mink, and great horned owls in rough descending order. In Cuba and Florida, the American crocodile and alligator can take a surprisingly large number of sandhill cranes, especially recent fledglings. Sandhill cranes defend themselves and their young from aerial predators by jumping and kicking. Actively brooding adults are more likely to react aggressively to potential predators to defend their chicks than wintering birds, which most often normally try to evade attacks on foot or in flight. For land predators, they move forward, often hissing, with their wings open and bills pointed. If the predator persists, the crane stabs with its bill (which is powerful enough to pierce the skull of a small carnivore) and kicks.
Status and conservation
In the 1930s, sandhill cranes were generally extirpated east of the Mississippi River, but their populations have recovered, with an estimated 98,000 in the region in 2018, a substantial increase over the previous year. Although sandhill cranes are not considered threatened as a species, the three southernmost subspecies are quite rare. Resident populations, not migratory birds, cannot choose secure breeding habitat. Many subpopulations were destroyed by hunting or habitat change. The greater sandhill crane proper initially suffered most; by 1940, probably fewer than 1,000 birds remained. Populations have since increased greatly again. At nearly 100,000, they are still fewer than the lesser sandhill crane, which, at about 400,000 individuals continent-wide, is the most plentiful extant crane.
Some migratory populations of sandhill cranes face population threats due to interspecies competition with snow geese. Since the 1990s, snow geese have eaten waste corn on which the cranes also rely prior to migration. Sandhill crane populations are also threatened by hunting. Hunting cranes is legal throughout the states of the Central Flyway, from the Dakotas and Wyoming south to Oklahoma and Texas. Nebraska is the sole state along the Central Flyway where hunting cranes is illegal. Despite losses from hunting, interspecies competition and other pressures such as habitat loss, the species has expanded its range. Since the early 2000s, the sandhill crane has expanded both its winter (nonbreeding) and breeding ranges northward, including into upstate New York. In the 21st century, parts of the Midwestern United States have seen an extensive rebound of the species.
The transplantation of wild birds and introduction of captive-reared birds into suitable low-population areas have been called viable management techniques.
The Mississippi sandhill crane has lost the most range; it used to live along most of the northern Gulf of Mexico coast, and its range was once nearly parapatric with that of its eastern neighbor. As of 2013, about 25 breeding pairs exist in an intensively managed population. The Mississippi Sandhill Crane National Wildlife Refuge—established in 1975 when fewer than 35 of the birds existed—has the biggest release program for cranes on Earth, and 90% of the cranes there were raised in captivity. The second viable egg from a two-egg nest was occasionally removed from the nests, starting in 1965, to become part of a captive flock. This breeding flock is divided between the Audubon Institute's Species Survival Center and White Oak Conservation in Yulee, Florida. These cranes have produced offspring for annual releases into the refuge.
A Mississippi sandhill crane was the first bird to hatch from an egg fertilized by sperm that was thawed from a cryogenic state. This occurred at the Audubon Institute, as part of this subspecies' endangered species recovery plan.
About 300 Cuban sandhill cranes exist; this is the least known of the populations.
In January 2019, 25 to 30 thousand cranes (both greater and lesser subspecies) were found wintering at the Whitewater Draw State Wildlife Area near McNeal in southeast Arizona.
Sandhill cranes have been tried as foster parents for whooping cranes in reintroduction schemes. This failed when the whooping cranes imprinted on their foster parents, later did not recognize other whooping cranes as their conspecifics, and unsuccessfully tried to pair with sandhill cranes, instead.
Sandhill cranes occasionally reach Europe as vagrants. The first British record was on Fair Isle in April 1981, and the second was in Shetland in 1991. Small groups have also been seen in parts of eastern China and Taiwan. In 2022, reports emerged of regular sightings of sandhill cranes in New Brunswick, on the Atlantic coast of Canada.
Images for kids
Sandhill crane in flight at the Llano Seco Unit of the Sacramento National Wildlife Refuge Complex in January 2022
|Mary the Jewess|