EP Tundra Swan Habitat Selection during the Nonbreeding Season

Primary Investigator:
Katelyn Weaver, M.Sc. Candidate

Supervisors:
Dr. Scott Petrie, Long Point Waterfowl Executive Director
Dr. Hugh Henry, University of Western Ontario
Dr. Michael Schummer, Long Point Waterfowl Scientist

Background

Eastern Population (EP) Tundra Swans (TUSWs) winter at the Great Lakes and along the Atlantic coast of the United States and breed from the North Slope of Alaska to the eastern side of the Hudson Bay in Canada, with migration corridors passing through the Great Lakes and northern Prairies.  Tundra Swans spend 29% of their time on breeding grounds and 52% on staging grounds. Extensive migrations are made in spring when the birds are at their lowest annual body mass and in fall when juveniles are likely continuing to grow and adults are replenishing lipid reserves utilized during the breeding season and wing moult. Due to the substantial time spent in migration and the energy requirements associated with this period, migratory habitat is considered especially important to this species.

During the mid-to-late 1900s, when wetlands were being rapidly converted for agricultural uses, TUSWs and other waterfowl began incorporating grain in their diets where seasonally available.  Including agricultural grains in previously aquatic diets was accompanied by changes in migration routes, range expansions, earlier arrival on spring stopover sites, increased fat stores and dramatic population increases for many populations of waterfowl, especially large-bodied Arctic nesters (e.g., Snow Geese). With agricultural practices continuing changes and advances in efficiency, availability of waste grain may be reducing for foraging waterfowl. As habitat selection represents greater use than availability of a habitat, it is important to understand the driving forces of seasonal selection of agricultural and aquatic habitats by waterfowl.

Project Description

Geographic and seasonal changes in habitat selection can alter the demography of avian migrants, yet research and conservation efforts are often logistically constrained to the breeding period. Therefore, the objective of this study was to determine habitat selection by TUSWs during the nonbreeding period (September – June). We used location data from 63 adult EP TUSW monitored by satellite telemetry to study broad scale habitat selection during the nonbreeding season. Location data was obtained from 12 TUSW marked in 1998 and 1999 by Long Point Waterfowl during autumn and spring migration, 41 TUSW marked in 2000 and 2001 by Dr. Khristi Wilkins and the US Fish and Wildlife Service at the Atlantic Coast during winter, and 10 TUSW marked in 2008 by Dr. Craig Ely and the US Geological Survey. Overall, we were able to track TUSW from spring 1998 to winter 2011.

By pairing TUSW location data with land cover data, Katelyn was able to determine use and availability of agricultural, open water and wetland habitats throughout the nonbreeding period. Katelyn used the habitat use and availability information to determine the selection intensity for each habitat type (how much the habitat was used relative to its availability). Understanding habitat selection by season is very important for conservation and management of Tundra Swans. Accurate knowledge of the habitat types swans are selecting could help predict ecological carrying capacities and determine which areas require protection.

Findings

Habitat selection varied seasonally and geographically and was likely influenced by changes in nutritional requirements and habitat and food availability. Tundra swans selected open water and agriculture in winter, and selected open water during migration, especially in the autumn, whereas wetlands were weakly selected during migration. There was a 2-fold increase in use of agriculture from autumn to spring. Selection for agriculture and wetlands changed continuously with latitude and longitude, whereas selection for open water changed discretely between the Atlantic Coast, Great Lakes and Prairies. Tundra swan habitat management should focus on protecting wetlands and open water habitats, while ensuring adequate availability of waste agricultural grains, especially during winter and spring.

Project Sponsors and Partners

Craig Ely
Kristi Wilkins
Long Point Waterfowl
NSERC Canada Graduate Scholarship
Queen Elizabeth II Graduate Scholarship
Toronto Sportsmen’s Show
TD Friends of the Environment Foundation
U.S. Fish and Wildlife Service

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