Habitat use by sandhill cranes wintering in Western Texas

About 80-90% of the 400,000+ mid-continent population of sandhill cranes (Grus canadensis) winter on the High Plains of western Texas. Habitat use by cranes wintering in the Rich Lake area was studied during January and February, 1979 and 1980. At least 150,000 cranes roosted on Rich Lake, and additional birds roosted on other pluvial lakes in the region. Percentage availability of each habitat type surrounding Rich Lake was compared to relative use by cranes, either by following radio-marked cranes or by systematic ground transects. Waste grain in harvested milo fields was the primary food. Milo stubble and playa lake habitats were used by cranes in greater (P < 0.05) and cotton stubble and native mesquite grasslands in lesser (P < 0.05) proportion than percentage availability. Hectares of milo stubble were 60% greater in 1979 than 1980, but the amount of waste grain in fields was three times greater in 1980. Fields disked or plowed prior to late February reduced the food base for wintering cranes. Pluvial lakes served as night roosts, and most drinking water was obtained from freshwater springs bordering the lakes. Daily mean distance cranes flew from Rich Lake was 10.8 km in 1979 and 7.8 km in 1980. Crane density, habitat availability, and mean daily distances flown from Rich Lake differed between 1979 and 1980. J. WILDL. MANAGE. 49(4):1074-1083 The western Texas High Plains have provided the principal winter habitat for sandhill cranes from mid-continental North America (Buller 1979) since at least the 1840's (Bailey 1928, Kendall 1929). From 320,000 to 440,000 cranes (80-90% of the mid-continent population) wintered in western Texas during this study (Iverson et al. 1985). Arrival began in late October; departures occurred in late February (Lewis 1977). Aggregations numbering to 200,000 birds concentrated in a few locations on the High Plains. Presence of the large concentrations was attributed to the limited availability of three essential resources in this semi-arid region: pluvial lakes for roost sites, fresh water for drinking, and waste milo grain in stubble fields (Iverson et al. 1985). The quality of winter habitat is important because cranes refuge in large numbers; depend on limited resources in the region; and are vulnerable to disturbance, water and cropland management practices, and habitat alteration. To describe and evaluate winter habitat use as a major element of the sandhill crane survival strategy, we quantified population evels, food availability, daily and seasonal habitat use, and daily and seasonal activity patterns of cranes wintering in western Texas. These parameters, coupled with quantification of physiological condition (Iverson 1981), provide data essential to management of the wintering population. This project was funded by Contract 14-180008-2133, Accelerated Res. Program for Migratory Shore and Upland Game Birds, administered by the Cent. Manage. Unit Tech. Comm. and the Migratory Bird and Habitat Res. Lab. , U.S. Fish and Wildl. Serv. The Oklahoma Coop. Wildl. Res. Unit has Oklahoma State Univ., Okla. Dep. of Wildl. Conserv. , U.S. Fish and Wildl. Serv. , and The Wildl. Manage. Inst. cooperating.