Dr. Scott Petrie, Long Point Waterfowl Executive Director
Dr. Hugh Henry, University of Western Ontario
Dr. Michael Schummer, Long Point Waterfowl Scientist
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. Therefore, the objective of this study is to determine habitat selection by Tundra Swans during the nonbreeding period (September – June). 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. Furthermore, if swans rely heavily on agricultural grains during spring migration as suspected, the switch to more economically viable agricultural products such as cotton and sugarcane could be detrimental to their population. The results of this study could also be used to make suggestions on proper placement of Industrial Wind Turbines to minimize impacts on swan migration and feeding.
Katelyn is using land cover information and location data obtained from satellite telemetry units attached to 63 EP Tundra Swans to explore habitat selection during the nonbreeding period. The telemetry data used in this study comes from the following sources:
1) Long Point Waterfowl studied Tundra Swan migration chronology in the late 1990′s by placing satellite transmitters on 12 Tundra Swans during their migration stopover at Long Point, Lake Erie.
2) Khristi Wilkins and the U.S. Fish and Wildlife Service (P.hD. Project) tagged an additional 41 Tundra Swans with satellite transmitters on their wintering grounds
between 2000-2002. The Tundra Swans in Wilkin’s study were used to determine migratory movement, survival, and population structure.
3) An additional 10 Tundra Swans were tagged in Alaska during the breeding period by Craig Ely and data from these birds spans from autumn 2008 – winter 2011.
Selection intensity is used to represent the strength of selection of agriculture, open water and wetlands. Selection intensity values are between 1.0 and -1.0 and values increase as the difference between use and availability increases. Preliminary results suggest:
1) Tundra Swans selected for agricultural fields in winter (0.07), and avoided agriculture approximate to availability during spring (-0.04) and especially in autumn (-0.24),
2) selection for open water was greater in autumn (0.32) than winter and spring (0.05), and,
3) selection for emergent wetlands decreased as TUSWs moved south and east towards their wintering areas.
Results suggest selection for wetlands was influenced by location whereas selection of agricultural fields and open water was influenced by location and seasonal events/nutritional requirements. Because selection intensity of agriculture was negative during spring and autumn, this suggests that agricultural habitats are abundant during these periods. A selection intensity of 0.32 for open water habitats during autumn suggests that conservation and management of open water habitats is very important at this time. Finally, the changing selection intensity of wetlands with location suggests availability of wetlands is limiting as swans move north and west in their range. Knowledge of TUSW selection for wetlands, open water and agricultural areas will contribute to our understanding of the species and help refine conservation strategies for the Eastern Population and potentially other grain eating waterfowl.
Project Sponsors and Partners
Long Point Waterfowl
NSERC Canada Graduate Scholarship
Toronto Sportsmen’s Show
TD Friends of the Environment Foundation
U.S. Fish and Wildlife Service