Grus americana

Based on DNA data, Grus grus, G. americana, G. monachus, and G. nigricollis form a monophyletic lineage apart from G. japonicus (Krajewski and Fetzner 1994), and the closest living relative of G. americana may be G. grus (Love and Deininger 1992).

Grus americana exhibits low mtDNA diversity; may have a single mtDNA haplotype (Snowbank and Krajewski 1995).

One self-sustaining population nests in Canada, winters primarily along the Texas coast; two additional reintroduced populations (one migrates Wisconsin-Florida, one nonmigratory in Florida); historically much more widespread; total wild population in 2006 was 338; with about 135 in captive flocks; numbers increasing; problems include habitat degradation, low productivity associated with drought, and mortality from collisions with powerlines along lengthy migratory route.

The historical range extended from the Arctic coast of North Amercica south to central Mexico, and from Utah east to New Jersey, South Carolina, Georgia, and Florida; in the 19th and 20th centuries, nesting occurred principally in the region extending from central Canada to the north-central United States (see CWS and USFWS 2007). Current distribution includes just three populations: (1) the Aransas-Wood Buffalo National Park Population that nests in Wood Buffalo National Park and adjacent areas in Canada (south-central Mackenzie and adjacent northern Alberta) and winters in coastal marshes in Texas, with significant migration stopovers in southern Saskatchewan, Nebraska, Kansas, and Oklahoma; (2) a reintroduced non-migratory Florida Population that occurs in central Florida; and (3) a reintroduced Eastern Migratory Population that migrates between Wisconsin (Necedah National Wildlife Refuge) and Florida (Chassahowitzka NWR) (CWS and USFWS 2007).

Extent of occurrence (breeding) appears to be less than 5,000 square kilometers.

Three populations currently exist (see Range Extent comments).

Historically, population declines were caused by shooting and destruction of nesting habitat in the prairies from agricultural development. The species was listed as endangered because of low population numbers, slow reproductive potential (sexual maturity is delayed and pairs average less than 1 chick annually), cyclic nesting and wintering habitat suitability, a hazardous 4,000 km migration route that is traversed twice annually, and many human pressures on the wintering grounds. Current threats to wild cranes include collisions with manmade objects such as power lines and fences, accidental shooting, predators (especially predation of flightless chicks), disease (avian tuberculosis has been documented in the Aransas-Wood Buffalo population, and both West Nile virus and H5N1 avian influenza virus are emerging new threats of unknown proportion to both captive and wild populations), habitat destruction and contamination, severe weather, and a loss of two-thirds of the original genetic material. Threats to the captive flock include disease, accidents, and limited genetic material. [Source: CWS and USFWS 2007]