USGS1995
Resident sandhill cranes formed a continuous population in Georgia and Florida and widely separated populations along the Gulf Coastal Plain of Texas, Louisiana, Mississippi, and Alabama (Figure). The Mississippi sandhill crane ( Grus canadensis pulla ) was one of the widely separated populations on the Coastal Plain that bred in pine savannas in southeastern Mississippi, just east of the Pascagoula River to areas just west of the Jackson County line, south to Simmons Bayou, and north to an east-west line 8-16 km (5-10 mi) north of VanCleave. Agricultural and industrial development including World War II ship building, fire suppression, and forestry practices destroyed much of the sandhill crane's habitat in Jackson County, Mississippi. The U.S. Fish and Wildlife Service (USFWS) added the Mississippi sandhill crane to the endangered species list in 1973 and established the Mississippi Sandhill Crane National Wildlife Refuge in 1974. The USFWS began captive breeding at the Patuxent Wildlife Research Center (PWRC) in 1965 to protect the subspecies during habitat restoration and to provide stock for reintroduction. Morphological, physiological, and genetic differences exist among crane subspecies (Aldrich 1972). Mississippi birds mature earlier and begin egg production about 6 weeks later than Florida sandhill cranes. Genetic studies (Dessauer et al. 1992; Jarvi et al. 1994) show a level of heterozygosity (see glossary) in the wild Mississippi population about half that in other sandhill cranes. As in other small populations, cranes seem to have genetic weaknesses. In the captive population, for example, 17% of all birds die from detectable heart murmurs and when released to the wild, 36% with heart murmur and 83% without heart murmurs survive for 1 year after release.