WHOOPING CRANE STAY LENGTH IN RELATION TO STOPOVER SITE CHARACTERISTICS

• Main Authors: CAVEN, ANDREW J., PEARSE, AARON T., BRANDT, DAVID A., Harner, Mary J., WRIGHT, GREG D., BAASCH, DAVID M., BRINLEY BUCKLEY, EMMA M., METZGER, KRISTINE L., RABBE,, MATTHEW R., LACY, ANNE E.
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 2022
• Subjects: Great Plains; Grus americana; habitat; machine learning; migration; stay length; stopover; wetlands; whooping crane; Animal Sciences; Behavior and Ethology; Biodiversity; Ornithology; Population Biology; Terrestrial and Aquatic Ecology; Wood Buffalo
• Online Access: https://digitalcommons.unl.edu/nacwgproc/397; https://digitalcommons.unl.edu/context/nacwgproc/article/1387/viewcontent/Caven_et_al._2022._Whooping_crane_stay_length_in_relation_to_stopover_site_characteristics.pdf

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 ...