Grus canadensis, Photo: National Biological Information Infrastructure
Grus canadensis Linnaeus, 1758
* Grus canadensis Report on ITIS
The Sandhill Crane (Grus canadensis) is a large crane of North America and extreme northeastern Siberia. The common name of this bird references habitat like that at the Platte River, on the edge of Nebraska's Sandhills in the American Midwest. This is the most important stopover area for the Lesser Sandhill Crane (Grus canadensis canadensis), with up to 450,000 of these birds migrating through annually.
Adults are gray overall; during breeding, the plumage is usually much worn and stained, particularly in the migratory populations, and looks nearly ochre. The Sandhill Crane has a red forehead, white cheeks and a long dark pointed bill. Its long dark legs trail behind in flight, and the long neck is kept straight in flight. Immature birds have reddish brown upperparts and gray underparts. The sexes look alike. Size varies among the different subspecies. This crane frequently gives a loud trumpeting call that suggests a French-style "r" rolled 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 single call of the male.
The only other large grayish-bodied bird of North America is the Great Blue Heron. This heron is of similar dimensions to the Sandhill Crane and is sometimes mistakenly called a crane, even though it is very different in plumage details and build. Like other herons, it flies with its neck tucked toward the body.
The sandhill crane's large wingspan, which is 6–8 feet when fully grown, makes this a very skilled soaring bird similar in style to hawks and eagles. Utilizing thermals to obtain lift, they can stay aloft for many hours, requiring only occasional flapping of their wings and consequently expending little energy. With migratory flocks containing hundreds of birds, they can create clear outlines of the normally invisible rising columns of air (thermals) that they ride.
The Sandhill Crane flies south for the winter. In their wintering areas they form flocks of over 10,000 birds. One place to observe this is at Bosque del Apache National Wildlife Refuge, 100 miles south of Albuquerque, New Mexico. There is an annual Sandhill Crane Festival in November.
The Sandhill Crane has one of the longest fossil histories of any extant bird. A 10-million-year-old crane fossil from Nebraska is often cited as being of this species, but this is more likely from a prehistoric relative or the direct ancestor of the Sandhill Crane and may not belong in the genus Grus. The oldest unequivocal Sandhill Crane fossil is "just" 2.5 million years old, over one and a half times older than the earliest remains of most living species of birds, which are 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 the present-day birds, even those Pliocene fossils were sometimes described as new species. Grus haydeni on the other hand may or may not have been a prehistoric relative of the living species, or it may actually comprise material of the Sandhill Crane and its ancestor.
Subspecies and evolution
There is considerable variation in size (much of which is clinal) and in migratory habits. A male of G. c. canadensis averages 7.4 lbs (3.34 kg), 39 in (98 cm) in length and has a wingspan of 5.3 ft (1.6 m). A male of G. c. tabida averages 11 lbs (5 kg), 47 in (119 cm) in length and has a wingspan of 7 ft (2.12 m). The southern subspecies (along with G. c. rowani) are intermediate, roughly according to Bergmann's Rule.
Three subspecies are resident; pulla of the Gulf Coast of the U.S., pratensis of Florida and Georgia and 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. This crane is a rare vagrant to China, South Korea and Japan and a very rare vagrant to western Europe.
Six subspecies have been recognized in recent times:
* Lesser Sandhill Crane, Grus canadensis canadensis
The Canadian Sandhill Crane is morphologically not reliably distinct and was never unequivocally accepted as valid subspecies. The other 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 2 major lineages, one including the Lesser Sandhill Crane or Little Brown Crane, the Arctic and the subarctic migratory population. 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 roughly to some time during the Late Pliocene or Early Pleistocene, some 2.3–1.2 million years ago (mya). It seems as if glaciation fragmented off a founder population of the Lesser Sandhill Crane, 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 G. canadensis and the Greater Sandhill Crane G. pratensis, which would include the other populations.
It appears as if the scant differences between southern Canadian and western U.S. populations 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 rowani may well be abandoned.
The two southern U.S. resident populations are somewhat more distinct, while the Cuban population has been comparatively little studied but appears to have been established on the island for a long time. These and the migratory Greater Sandhill Crane proper form a group of lineages that diverged much more recently from a range in the southern U.S. and maybe northern Mexico, where they would have been resident. The southern migratory population would then represent a later re-expansion which (re-)evolved their migratory habits independent from the northernmost birds, the geographically separated populations expanding rapidly in numbers when more habitat was available as the last ice age ended.
Status and conservation
Though the Sandhill Crane is not considered threatened as a species, the three southernmost subspecies are quite rare. While the migratory birds could at least choose secure breeding habitat, the resident populations could not, and many subpopulations were destroyed by hunting or habitat change. However, initially the Greater Sandhill crane proper suffered most from persecution; by 1940 probably fewer than 1,000 birds remained. They have since increased greatly again, though with nearly 100,000 individuals they are still less plentiful than the Lesser Sandhill Crane, which numbers over 400,000 individuals, making the species the most plentiful crane alive today.
The Florida Sandhill Crane is far less common, with some 5,000 individuals remaining. They are most threatened by habitat destruction and probably depend on human management in the long run. In Florida, it is protected, and if killed, carries a very high monetary penalty. This subspecies is under protection of state and federal law at this time. Since the loss of habitat is a somewhat controllable cause of a declining population, habitat preservation is a valuable management measure. The current outlook for the Florida sandhill crane, if it can be maintained on the protected habitats, is good. Transplanting wild birds, as well as introducing captive-reared birds into suitable areas where crane numbers are low, appears to be a viable technique in the management of this threatened species. It is hoped that these management strategies, plus continued ecological research, will prevent the Florida sandhill crane from reaching a more critical status.
The Mississippi Sandhill Crane has most drastically declined in range; it used to occur along most of the northern Gulf of Mexico coast and its range was at one time nearly parapatric with that of its eastern neighbor (compare the Mottled Duck); today only 25 breeding pairs exist in an intensively managed population, but this seems at least stable in recent times. Some 300 Cuban Sandhill Cranes remain; this is the least-known of the populations.
The Mississippi Sandhill Crane has become the first bird to have a young hatched where an egg was fertilized by a sperm that was previously thawed out from a cryogenic state. This occurred at the Audubon Institute as part of this subspecies' Recovery Plan.
Sandhill Cranes have been used as foster parents for Whooping Crane eggs and young in reintroduction schemes for that species. This project failed as these foster-raised Whooping Cranes imprinted on their foster parents and later did not recognize other Whooping Cranes as their conspecifics – attempting instead, unsuccessfully, to pair with Sandhill Cranes. ..
1. ^ Allaboutbirds.org
* Archibald, George W. & Meine, Curt (1996): 7. Sandhill Crane. In: Del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.): Handbook of Birds of the World (Volume 3: Hoatzin to Auks): 85, plate 5. Lynx Edicions, Barcelona. ISBN 84-87334-20-2
Source: Wikipedia, Wikispecies: All text is available under the terms of the GNU Free Documentation License