Common Terns (Sterna hirundo) breeding at inland lakes in North America have experienced significant population declines since the 1960s. Although management actions aimed at mitigating effects of habitat loss and predation have been largely effective, numbers continue to decline, which suggests that the population may be limited during the nonbreeding season. Between 2013 and 2015, we used light-level geolocators to track Common Terns nesting at 5 inland colonies--from Lake Winnipeg in Manitoba, Canada, to the eastern Great Lakes region of the United States and Canada--to identify migratory routes and stopover and wintering sites and to determine the strength of migratory connectivity among colonies. Within 46 recovered tracks, we found evidence of a longitudinal gradient in use of migration routes and stopover sites among colonies and identified major staging areas in the lower Great Lakes and at inland and coastal locations along the Atlantic coast, Florida, and the Gulf of Mexico. Low migratory connectivity across inland colonies illustrates high intermixing within wintering sites, with many birds spending the nonbreeding season in Peru (70%) and the remainder spread throughout the Gulf of Mexico, Central America, and northwestern South America. While the large spatial spread and intermixing of individuals during the nonbreeding season may buffer local effects of climate change and human disturbance, the aggregation of individuals along the coast of Peru could make them vulnerable to events or changes within this region, such as increased frequency and intensity of storms in the Pacific, that are predicted to negatively influence breeding productivity and survival of Common Terns. Identifying sources of mortality during the nonbreeding season, quantifying winter site fidelity, and reinforcing the importance of continued management of inland breeding colonies are vital priorities for effective conservation and management of this vulnerable population.
Bibliographical noteFunding Information:
We thank the many people involved in forming this collaborative effort—most especially I. Nisbet, for his advice, guidance, and review of the manuscript; and S. Lewis, for his long-term dedication to conservation of Common Terns in the Great Lakes region. We are grateful to members of the AOU-COS 2015 light-level geolocation workshop in Norman, Oklahoma, and the 2016 NAOC workshop in Washington, D.C., specifically to E. Rakhimberdiev, E. Bridge, N. Seavy, and M. Hallworth for their assistance to A.B. during these workshops. We are also thankful for project advice and training from J. Arnold, S. Oswald, M. Mallory, R. Porter, G. Kramer, N. Walton, and J. Bednar as well as field assistance from R. Rodriguez, E. Hannan, N. Barlow, C. Dale, A. Foran, J. Galloway, B. Moray, N. Shephard, A. Stupich, R. Weeber, K. Rewinkel, and M. Minchak; and for logistical support from S. Vanneste, J. Hughes, L. Kress, P. Martin, B. Magnusson, S. Surprenant, and S. Song. DNA analysis was conducted in part by A. Idrissi, L. Gauthier, A. Lekorchi, C. Robert, and G. Savard. F.C. is grateful to the University of Michigan Biological Station for decades of logistical support for Common Tern research in the Great Lakes. Funding statement: Funding was provided by the U.S. Fish and Wildlife Service (USFWS; agreement nos. F11AP00081 and F11AP00515); the USFWS Great Lakes Fish and Wildlife Restoration Act (agreement no. F16AP01000); the Coastal Zone Management Act of 1972, as amended, administered by the Office for Coastal Management, National Oceanic and Atmospheric Administration, under award no. NA16NOS4190119 provided to the Minnesota Department of Natural Resources for Minnesota’s Lake Superior Coastal Program; the Minnesota and Wisconsin departments of natural resources; and various internal grants from the University of Minnesota, the Natural Resources Research Institute, and the University of Minnesota Conservation Sciences graduate program to A.B. to fund fieldwork and purchase geolocators. New York State Department of Environmental Conservation and Cornell Lab of Ornithology funded the purchase of geolocators and management of the Oneida Lake colony. F.C.’s contribution to this research was supported by the USDA National Institute of Food and Agriculture, Hatch project no. 1007020. Funding for the Canadian portion of the study was through Canadian Wildlife Service, Environment and Climate Change Canada. Ethics statement: We acquired all necessary permitting for handling and marking Common Terns in the United States and Canada (2013–2016). This project was approved by the USGS Bird Banding Laboratory (permit nos. 05322 and 08781) and the Canadian Wildlife Service Bird Banding Office (permit no. 10431), the Wisconsin Department of Natural Resources Animal Care and Use Committee, the Cornell University Animal Care and Use Committee (protocol no. 2001-0091), and the Animal Care Committee of the Wildlife and Landscape Science Directorate and the Canadian Wildlife Service Ontario, Environment Canada, with due regard for the Guidelines of the Canadian Council of Animal Care. Author contributions: D.M., A.M., E.C., S.M., F.S., F.C., G.N., and P.C. conceived the idea and supervised research. D.M., C.P., J.C., A.M., E.C., P.C., A.B., and F.S. collected data. S.L. and A.B. analyzed the data. A.B., S.L., and A.M. wrote the paper, with all authors contributing substantially to revisions.
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- Sterna hirundo
- geolocation by light
- migratory connectivity