76 



Birds — Our Living Rf sources 



Table 1. Estimated numhers of 

 Mississippi sandhill cranes on the 

 Mississippi Sandhill Crane 

 National Wildlife Refuge, 1924- 

 93, 



Status and Trends 



Population Decline 



In the 1800"s the species was abundant 

 eniHigh for farmers to consider it a pest. 

 Although population studies only started 

 recently, it appears the population has been 

 small for most of this century (Table I ). 



Until the 194()"s, the human population in 

 Jackson County was small, and the remnant 

 population of Mississippi sandhill cranes 

 remained stable. The suitable pine sa\anna 

 habitat shrunk from over 40.?()() ha (100.000 

 acres) in 1940 to 10,530 ha (26.000 acres) in the 

 1960"s, which were designated as critical habi- 

 tat by the USFWS. The USFWS requested a 

 population study in 1960 when Mississippi pro- 

 posed building Interstate Highway 10 through 

 the last of the crane habitat. The Nature 

 Conservancy, the U.S. Department of 

 Transportation, and State of Mississippi donat- 

 ed land to the refuge. 



Recent Reintroductions 



The first releases of hand-reared birds failed. 

 Thus, releases of Mississippi sandhills on the 

 refuge during the 1980"s were birds raised by 

 their parents or surrogate parents. These parent- 

 reared birds proved wilder than the hand-reared 

 birds and adapted well to the pine savanna. 

 Unfortunately, the parent-rearing technique 

 reduced production and increased expenses. 



The PWRC developed a new hand-rearing 

 technique that visually isolated chicks from 

 humans and imprinted them on adult sandhill 

 cranes in the chick-rearing area. Caretakers 

 dressed in sheets to hide their human form when 

 handling birds, and encounters with cranes were 

 limited. Ju\eniles were placed in socialization 

 pens in the fall to form three cohorts (parent- 



reared, hand-reared, and a mixed group). A gen- 

 tle release on the refuge allowed the birds to 

 leave the release pen when ready and to return 

 for food for a period after release. Surprisingly, 

 a greater percentage of hand-reared birds has 

 survived than the parent-reared birds, although 

 both groups have paired and produced fertile 

 eggs. The releases increased the refuge popula- 

 tion from 44 in 1988 to \?>5 in 1993 ("Table 1 ). 



Status in .Jackson County, Mississippi 



The population decline of the Mississippi 

 sandhill crane retlects the loss of the mesic and 

 hydric pine savanna once abundant in the area. 

 Savannas occur on coastal terraces, elevated 

 ridges, and uplands. Fire frequency and intensi- 

 ty, combined with soil type and hydrology, pro- 

 vide successional regulation of the savanna. 

 Woody, forested communities replace the 

 savanna without fire. Before ditching, the fiat 

 topography of the terraces allowed sheet flow of 

 water across the terraces and supported exten- 

 sive areas of open savanna. When the refuge 

 was established, about 75% of the crane savan- 

 nas had been destroyed (by residential or com- 

 mercial development) or changed to one of sev- 

 eral different forest types. Only 59c of the orig- 

 inal savanna type that supported the cranes 

 remains on the Gulf Coastal Plain. For this rea- 

 son. Mississippi sandhill cranes now occur only 

 on the refuge and adjacent private lands in 

 southeastern Mississippi. 



The Mississippi sandhill crane population 

 nests only on the 7,813-ha ( 19,300-acre) refuge. 

 The only other large tract of remnant savanna 

 that might be suitable nesting habitat exists 

 southeast of the refuge on the proposed Grand 

 Bay National Wildlife Refuge. Savanna used by 

 the Mississippi sandhill crane exists as highly 

 fragmented remnants that the refuge must man- 

 age to provide nesting, foraging, and roosting 

 sites (Table 2). 



Mortality and natural recruitment may also 

 restrict population viability. Predation (primari- 

 ly mammalian) causes high mortality during the 

 first year of life. Other factors that may limit 

 populations include tumors, contaminants, 

 microbial pathogens, and parasites. The preva- 

 lence of tumors in the wild Mississippi sandhill 

 crane population far exceeds that expected in 

 other birds and mammals. 



Table 2. Mississippi sandhill crane nesting sites on 

 refuse, hv habitat. 



