Sandhill crane
The sandhill crane is a species complex of large cranes of North America and extreme northeastern Siberia. The common name of this bird refers to its habitat, such as the Platte River, on the edge of Nebraska's Sandhills on the American Great Plains. Sandhill cranes are known to frequent the edges of bodies of water. The central Platte River Valley in Nebraska is the most important stopover area for the nominotypical subspecies, the lesser sandhill crane, with up to 450,000 of these birds migrating through annually.
Taxonomy
In 1750, British naturalist George Edwards included an illustration and a description of the sandhill crane in the third volume of his A Natural History of Uncommon Birds, referring to the species as the 'Brown and Ash-colour'd Crane.' Edwards based his hand-colored etching on a preserved specimen that had been brought to London from the Hudson Bay area of Canada by James Isham. When in 1758, Swedish naturalist Carl Linnaeus updated his Systema Naturae for the tenth edition, he placed the sandhill crane with herons and cranes in the genus Ardea. Linnaeus included a brief description, coined the binomial name Ardea canadensis, and cited Edwards' work.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 German naturalist Ludwig Reichenbach in 1853.
The specific epithet canadensis is the modern Latin word for "from Canada".
Five subspecies are recognised:
- A. c. canadensis – northeast Siberia through Alaska and northern Canada to Baffin Island
- A. c. nesiotes – Cuba and Isla de la Juventud
- A. c. pratensis – Georgia and Florida
- A. c. pulla – Mississippi
- A. c. tabida – southern Canada and west-central United States
Description
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, while the average weight of females is, with a range of 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 upper parts and gray underparts. The juveniles do not have the characteristic red foreheads, making distinguishing the young from the parents possible, even when they are the same height.
The sexes look alike. Sizes vary among the different subspecies; the typical height of these birds is around. Their wing chords are typically, tails are, the exposed culmens are long, and the tarsi measure. Wingspan is 200 cm.
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, 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 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, south of Albuquerque, New Mexico. An annual Sandhill Crane Festival is held there in November.
Fossil record
Sandhill cranes have one of the longest fossil histories of any extant bird. A 10-million-year-old crane fossil from Nebraska is said to be of this species, but this may be from a prehistoric relative or ancestor of sandhill cranes, of a genus other than Grus and Antigone. The oldest unequivocal sandhill crane fossil is 2.5 million years old, older by half than the earliest remains of most living species of birds, primarily found from after the Pliocene/Pleistocene boundary some 1.8 million years ago. As these ancient sandhill cranes varied as much in size as present-day birds, those Pliocene fossils are sometimes described as new species. Grus haydeni may have been a prehistoric relative, or it may comprise material of a sandhill crane and its ancestor.Subspecies and evolution
Sandhill cranes vary considerably in size and in migratory habits. A female of A. c. canadensis averages in weight, in length, and in wingspan. A male of A. c. tabida averages,, and in comparison. The southern subspecies are intermediate, roughly according to Bergmann's rule.Three subspecies are resident: A. c. pulla of the Gulf Coast of the U.S., A. c. pratensis of Florida and Georgia, and A. c. nesiotes of Cuba. The northern populations exist as fragmented remains in the contiguous U.S. and a large and contiguous population from Canada to Beringia. These migrate to the Southwestern United States and Mexico. These cranes are rare vagrants to China, South Korea, and Japan and very rare vagrants to Western Europe.
Six subspecies have been recognized in recent times:
- Lesser sandhill crane, A. c. canadensis
- Cuban sandhill crane, A. c. nesiotes – ESA: endangered
- Florida sandhill crane, A. c. pratensis
- Mississippi sandhill crane, A. c. pulla – ESA: endangered
- Canadian sandhill crane, A. c. rowani
- Greater sandhill crane, A. c. tabida
Some authorities no longer recognize Canadian sandhill crane as a distinct subspecies, as insignificant genetic differentiation and minimal morphological differentiation exist between the greater sandhill crane and it. The others can be somewhat more reliably distinguished in hand by measurements and plumage details, apart from the size differences already mentioned. Unequivocal identification often requires location information, which is often impossible in migrating birds.
Analysis of control-region mtDNA haplotype data shows two major lineages. The Arctic and the subarctic migratory population includes the lesser sandhill cranes. The other lineages can be divided into a migratory and some indistinct clusters, which can be matched to the resident subspecies. The lesser and greater sandhill cranes are quite distinct, their divergence dating to roughly 2.3–1.2 million years ago, sometime during the Late Pliocene or Early Pleistocene. Glaciation seemingly fragmented off a founder population of lesser sandhill cranes, because during each major ice age, its present breeding range was frozen year-round. Still, sandhill cranes are amply documented from fossil and subfossil remains right to the modern era. Conceivably, they might be considered distinct species already, a monotypic A. canadensis and the greater sandhill crane, A. pratensis, which would include the other populations.
The scant differences between southern Canadian and western U.S. populations appear to result from genetic drift, due to the recent reduction in population and range fragmentation. Until the early 20th century, the southern migratory birds occupied a much larger and continuous range. Thus, the subspecies A. c. rowani may well be abandoned.
The two southern U.S. resident populations are somewhat more distinct. The Cuban population has been comparatively little studied, but appears to have been established on the island for a long time. They and the migratory greater sandhill cranes proper may form a group of lineages that diverged much later from a range in the southern U.S. and maybe northern Mexico, where they were resident. The southern migratory population would then represent a later re-expansion, which evolved their migratory habits independent from the northernmost birds, the geographically separated populations expanding rapidly when more habitat was available as the last ice age ended.