Abstract
Habitat use patterns and food habits of whooping cranes (Grus americana) and sandhill cranes (Grus canadensis) were studied on the Aransas National Wildlife Refuge, Texas between November 1982 and April 1985. Five upland pastures received different burning and grazing treatments each year. The effect of treatments on food abundance and upland vegetation was monitored, along with crane use of upland pastures. Based on fecal sample analysis, whooping cranes used a variety of foods, including blue crabs (Callinected sapidus), clams (Tagellus spp.), snails (Melampus coffeus), acorns (Quercus virginiana), and wolfberry (Lycium caroliniaum). Sandhill cranes consumed primarily acorns, insects, and wolfberry. Use of foods by both species was highly variable within and between years. Periodic upland burning increased the visual openess of the habitat, oak stem density, and the availability of acorns. Grazing reduced the abundance of wolfberry, insects, and freshwater aquatic organisms, and resulted in increased levels of human disturbance. On the uplands, approximately 60% of all whooping crane sightings and 92% of all sandhill crane sightings occurred on recently burned upland pastures where acorn densities were high. Whooping cranes used grazed pastures only during years of high acorn abundance. Less than 6% of all sandhill crane sightings occurred on grazed pastures. When bay salinities were above 23 ppt, whooping cranes used upland freshwater drinking sources. Whooping cranes selected and used portions of upland pastures which were open, close to the wetland edge, and away from sources of human disturbance. These findings suggest that whooping cranes tend to optimize energy and nutrient intake by foraging in habitats where food is most available, and by selecting foraging sites that may minimize flight, disturbance, and predator avoidance behavior.
Hunt, Howard Emery (1987). The effects of burning and grazing on habitat use by whooping cranes and sandhill cranes on the Aransas National Wildlife Refuge, Texas. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -746718.