US Geological Survey
Date of this Version
2005
Abstract
We used site evaluation data collected during 1977–1999 to examine patterns of habitat use by whooping cranes (Grus Americana) during migration through the United States portion of the Wood Buffalo–Aransas flyway. We examined characteristics of 3 types of stopover habitats: 1) roost sites (n = 141 records), 2) feeding sites (n = 306), and 3) dual-use sites (i.e., where observer recorded cranes as using a site for both roosting and feeding (n = 248). Results in spring were influenced by the large number of records from Nebraska (> 67% of spring records) and in fall by frequent observations on Salt Plains and Quivera National Wildlife Refuges and Cheyenne Bottoms State Wildlife Area. Palustrine wetlands were the most commonly recorded wetland system (68.8%) used by whooping cranes; riverine wetlands accounted for 21.6% and lacustrine wetlands 9.6% of site evaluation records. Riverine sites were common only in Nebraska, where they accounted for 59.0% of roost sites. All social groupings of whooping cranes used palustrine wetlands for both roosting and feeding, whereas most of the whooping cranes found on riverine roosts were single cranes or nonfamily groups. Most wetlands used by cranes were seasonally or semipermanently flooded. Observers found whooping cranes on a wide range of wetland sizes. River widths ranged from 36 to 457 m and averaged 227 ± 88 (SD) m. Maximum depths of wetlands on which observers saw cranes ranged from 3 to 305 cm and averaged 51 ± 41 cm. Specific sites within wetlands where observers recorded cranes feeding or roosting averaged 18 ± 11 cm (range 3&#;-61 cm). Observers described most wetlands as having soft substrates, low shoreline slope (< 5%), and clear or turbid water. Riverine roost sites and dual-use sites were consistent in their lack of vegetation, but palustrine sites varied in types of emergent vegetation and their distribution. Feeding sites were largely upland crops, with lower occurrence of seasonal or permanent wetlands, or upland perennial cover. At dual-use sites, cranes were most often found in palustrine permanent or seasonally flooded wetlands. In spring, observers recorded cranes most frequently feeding on row-crop stubble, with lesser use of small grain stubble and green crops. In fall, observers found cranes frequently on green crops, small-grain stubble, and row-crop stubble. Woodland habitat occurred adjacent to > 70% of riverine roost sites but adjacent to < 8% of palustrine roost sites. All riverine roosts and about half of palustrine roost sites also had adjacent upland cover; upland cropland was common for both. The most common habitats adjacent to feeding and dual-use sites were cropland and upland perennial cover. About two-thirds of feeding sites were < 0.8 km from palustrine roost sites, whereas over half of riverine roost sites were > 1.2 km from feeding sites. More than two-thirds of sites where observers found cranes were <0.8 km from human developments; 58% of observations were > 0.8 km from utility (power or phone) lines. Visibility varied by site use and wetland system. Private ownership accounted for > 80% of feeding sites used by whooping cranes; federal ownership accounted for most ownership of roost sites. More than 90% of roost sites that were under federal or state ownership were considered secure, whereas security of roosts on private lands was evenly split between secure and threatened. These observational data provide further insights into habitats used by migrant whooping cranes, but further investigations into habitat use patterns are needed.
Comments
Published in PROCEEDINGS NORTH AMERICAN CRANE WORKSHOP 9:79-104.