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Date: 2022
Authors:
ANDREW J. CAVEN, Platte River Whooping Crane Maintenance Trust
AARON T. PEARSE, USGS Northern Prairie Wildlife Research Center
DAVID A. BRANDT, USGS Northern Prairie Wildlife Research Center
MARY J. HARNER, University of Nebraska at Kearney
GREG D. WRIGHT, USFS Nebraska National Forest
DAVID M. BAASCH, Platte River Whooping Crane Maintenance Trust
EMMA M. BRINLEY BUCKLEY, University of Nebraska at Kearney
KRISTINE L. METZGER, U.S. Fish and Wildlife Service
MATTHEW R. RABBE, U.S. Fish and Wildlife Service
ANNE E. LACY, International Crane Foundation
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Citation:
Caven, A. J., A. T. Pearse, D. A. Brandt, M. J. Harner, G. D. Wright, D. M. Baasch, E. M. Brinley Buckley, K. L. Metzger, M. R. Rabbe, and A. E. Lacy. 2022. Whooping crane stay length in relation to stopover site characteristics. Proceedings of the North American Crane Workshop 15:6-33.
Abstract:
Whooping crane (Grus americana) migratory stopovers can vary in length from hours to more than a month. Stopover
sites provide food resources and safety essential for the completion of migration. Factors such as weather, climate, demographics
of migrating groups, and physiological condition of migrants influence migratory movements of cranes (Gruidae) to varying
degrees. However, little research has examined the relationship between habitat characteristics and stopover stay length in cranes.
Site quality may relate to stay length with longer stays that allow individuals to improve body condition, or with shorter stays
because of increased foraging efficiency. We examined this question by using habitat data collected at 605 use locations from
449 stopover sites throughout the United States Great Plains visited by 58 whooping cranes from the Aransas–Wood Buffalo
Population tracked with platform transmitting terminals. Research staff compiled land cover (e.g., hectares of corn; landscape
level) and habitat metric (e.g., maximum water depth; site level) data for day use and evening roost locations via site visits and
geospatial mapping. We used Random Forest regression analyses to estimate importance of covariates for predicting stopover
stay length. Site-level variables explained 9% of variation in stay length, whereas landscape-level variables explained 43%. Stay
length increased with latitude and the proportion of land cover as open-water slough with emergent vegetation as well as alfalfa,
whereas stay length decreased as open-water lacustrine wetland land cover increased. At the site level, stopover duration increased
with wetted width at riverine sites but decreased with wetted width at palustrine and lacustrine wetland sites. Stopover duration
increased with mean distance to visual obstruction as well as where management had reduced the height of vegetation through
natural (e.g., grazing) or mechanical (e.g., harvesting) means and decreased with maximum water depth. Our results suggest that
stopover length increases with the availability of preferred land cover types for foraging. High quality stopover sites with abundant
forage resources may help whooping cranes maintain fat reserves important to their annual life cycle.
The North American Crane Working Group provides free and open access to articles in Proceedings of the North American Crane Workshop. No additional permission is required for unrestricted use, distribution, or reproduction in any medium, provided that the original work here is properly cited. Complete Proceedings are also available for download or purchase.
© 2022 North American Crane Working Group
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