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Loon Program - Maine and New Hampshire
Loon Program - Maine and New Hampshire

Rangeley Lakes Long-term Monitoring: Maine and New Hampshire

The Rangeley Lakes study is the longest running monitoring effort of a uniquely color-marked loon population in North America. Shoreline nest placement and the loon's limited mobility on land make loon nests vulnerable to failure caused by water level fluctuations. Due to this sensitivity, the U.S. Fish and Wildlife Service (USFWS), Maine Inland Fisheries and Wildlife, and other wildlife agencies identified Common Loons as a species to be evaluated in connection with the Federal Energy Regulatory Commission (FERC) relicensing of reservoirs.

Lead Investigator: Alex Dalton
Contributing BRI Staff: David Evers, Bill Hanson, Jeff Fair

Project Overview

Project Overview

Partnered with Brookfield Renewable Energy and in cooperation with New Hampshire’s Loon Preservation Committee, BRI monitors nearly 200 territorial breeding pairs of Common Loons in northeastern New Hampshire and western Maine.

BRI biologists use nearly 80 artificial nesting islands (rafts) as the primary management tool in mitigating the impacts of water level fluctuations on nesting loons. Current efforts characterize and monitor the demographics of the breeding population, environmental exposure and effects of mercury and lead, incidence of diseases (e.g., avian influenza), and ecological impacts from reservoir operations.

Overall Study Goals

Overall Study Goals

  • Maintain nearly 80 artificial nesting rafts for Common Loons on reservoirs in the Rangeley Lakes region and monitoring egg laying rates and hatching success
  • Capture and color-band adult and juvenile loons (more than 400 loons from this area have been banded to date)
  • Monitor breeding territories on a weekly basis for overall breeding success, site fidelity, and individual performance of uniquely color-banded adult loons
  • Determine local and long-distance movements of breeding loons
  • Develop a long-term baseline for methylmercury availability and monitor the relationship of mercury body burdens and effects of mercury on physiology, behavior, productivity, and survival

Changing Water Levels Infographic



  • Mitro, M. G., D. C. Evers, M. W. Meyer, and W. H. Piper. 2010. Common Loon survival rates and mercury in New England and Wisconsin. Journal of Wildlife Management 72:665-673.
  • Evers, D.C., L. Savoy, C.R. DeSorbo, D. Yates, W. Hanson, K.M. Taylor, L. Siegel, J.H. Cooley, M. Bank, A. Major, K. Munney, H.S. Vogel, N. Schoch, M. Pokras, W. Goodale, and J. Fair. 2008. Adverse effects from environmental mercury loads on breeding common loons. Ecotoxicology 17:69-81.
  • DeSorbo, C.R., K.M. Taylor, D.E. Kramar, J. Fair, J.H. Cooley, Jr., D.C. Evers, W. Hanson, H.S. Vogel, and J.L. Atwood. 2007. Reproductive advantages for Common Loons using rafts. Journal of Wildlife Management 71 (4):1206-1213.
  • Evers, D.C., Y.J. Han, C.T. Driscoll, N.C. Kamman, M.W. Goodale, K.F. Lambert, T.M. Holsen, C.Y. Chen, T.A. Clair, and T. Butler. 2007. Identification and Evaluation of Biological Hotspots of Mercury in the Northeastern U.S. and Eastern Canada. BioScience 57:29-43.
  • Evers, D. C., N. M. Burgess, L. Champoux, B. Hoskins, A. Major, W. M. Goodale, R. J. Taylor, R. Poppenga, and T. Daigle. 2005. Patterns and interpretation of mercury exposure in freshwater avian communities in northeastern North America. Ecotoxicology 14:193-221.
  • Evers, D.C. and T.A. Clair. 2005. Mercury in Northeastern North America: a synthesis of existing databases. Ecotoxicology 14:7-14.
  • Haefele, H. J., I. Sidor, D. C. Evers, D. E. Hoyt, and M. A. Pokras. 2005. Hematologic and physiologic reference ranges for free-ranging adult and young Common Loon (Gavia immer). Journal of Zoo and Wildlife Medicine 36:385–390.
  • Evers, D.C., K. M. Taylor, A. Major, R. J. Taylor, R. H. Poppenga, and A. M. Scheuhammer. 2003. Common Loon eggs as indicators of methylmercury availability in North America. Ecotoxicology 11:6981.
  • Evers, D.C., J.D. Kaplan, M.W. Meyer, P.S. Reaman, W.E. Braselton, A. Major, N. Burgess, and A.M. Scheuhammer. 1998. Geographic trend in mercury measured in Common Loon feathers and blood. Environmental Toxicology and Chemistry 17:173-183.


Known for its rocky coastline, rolling mountains, and expansive forests, Maine is also home to approximately 2,600 water bodies that are larger than 10 acres in size.
Across this landscape, an estimated 1,700 territorial pairs of Common Loons breed each summer. With their haunting calls and distinctive black and white plumage, loons are emblematic of the north woods in this state. While this population of loons is healthy, current environmental threats require continuous loon monitoring and public outreach efforts to ensure this trend is not reversed.

Download the Draft Maine Status Report for the Common Loon here.

Photo Credits: Header photo © BRI-Jonathan Fiely; Reservoir lake © BRI-Deborah McKew; Loon nesting on shore © BRI-Jonathan Fiely; Infographic © BRI-Adelaide Tyrol/RavenMark; Rangeley Lake © BRI-Deborah McKew
Biodiversity Research Institute