Christopher R DeSorbo

Publications (4)4.38 Total impact

• Article: Reproductive Advantages for Common Loons Using Rafts

  CHRISTOPHER R. DESORBO, KATE M. TAYLOR, DAVID E. KRAMAR, JEFF FAIR, JOHN H. COOLEY JR, DAVID C. EVERS, WILLIAM HANSON, HARRY S. VOGEL, JONATHAN L. ATWOOD
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  ABSTRACT: Artificial nesting islands, or rafts, are often deployed in common loon (Gavia immer) breeding territories to decrease negative impacts of mammalian predation and water-level fluctuations on nesting success. The management value of rafts has been demonstrated in other studies; however, no published studies have quantified the use or associated reproductive benefits of rafts on lakes exhibiting water-level fluctuations. These lakes constitute a major portion of loon nesting habitat in New England and the Midwest. We used long-term data sets from loon survey and raft management efforts on lakes with stable (SWL) and fluctuating water levels (FWL) in New Hampshire and Maine, USA, to compare raft-use patterns on both types of lakes. We then modeled the influence of percentage of nesting attempts on rafts, lake fluctuation type, and human development index on nesting success as a function of the number of nesting attempts. Loons used 76% of all rafts for nesting, and initial use patterns were similar between SWL and FWL lakes. Half (51%) of rafts used for nesting were first used during the initial year of deployment and 90% of those used were used by the third year. Based on our model, we would expect to see an 8.6% increase in nesting success associated with each successive categorical increase in raft use (0–33%, 33–60%, 60–100%). Nesting success varied with lake fluctuation type, increasing by 21.4% from FWL to SWL types. Our model estimated a 12.8% decrease in nesting success associated with an increasing human development index. Naturally nesting loons on FWL lakes are likely to display mean nesting success levels lower than those needed to sustain populations. We suggest that natural nesting habitat on lakes with fluctuating water levels during the loon nesting season may constitute an ecological trap warranting consideration of raft management. Findings in this study are germane for managing breeding loon populations, particularly those on reservoirs requiring permits from the Federal Energy Regulatory Commission.
  Journal of Wildlife Management 12/2010; 71(4):1206 - 1213. · 1.52 Impact Factor
• Source

  Available from: David E Yates

  Article: Adverse effects from environmental mercury loads on breeding common loons.

  David C Evers, Lucas J Savoy, Christopher R DeSorbo, David E Yates, William Hanson, Kate M Taylor, Lori S Siegel, John H Cooley, Michael S Bank, Andrew Major, Kenneth Munney, Barry F Mower, Harry S Vogel, Nina Schoch, Mark Pokras, Morgan W Goodale, Jeff Fair
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  ABSTRACT: Anthropogenic inputs of mercury (Hg) into the environment have significantly increased in the past century. Concurrently, the availability of methylmercury (MeHg) in aquatic systems has increased to levels posing risks to ecological and human health. We use the common loon (Gavia immer) as an upper trophic level bioindicator of aquatic Hg toxicity in freshwater lakes. Multiple endpoints were selected to measure potential negative impacts from MeHg body burdens on behavior, physiology, survival and reproductive success. A robust spatio-temporal dataset was used that included nearly 5,500 loon Hg measurements over an 18-year period. We measured significant changes related to elevated MeHg body burdens, including aberrant incubation behavior, lethargy, and wing area asymmetry. Mercury body burdens in adult loons increased an average of 8.4% per year. Increasing Hg body burdens reduced the number of fledged chicks per territorial pair, with highest risk loons producing 41% fewer fledged young than our reference group. Our multiple endpoints establish adverse effect thresholds for adult loons at 3.0 ug/g (wet weight) in blood and 40.0 ug/g (fresh weight) in feathers. Mercury contamination in parts of Maine and New Hampshire is a driving stressor for creating breeding population sinks. Standardized monitoring programs are needed to determine if population sinks occur elsewhere and to track aquatic ecosystem responses to changes in Hg emissions and deposition.
  Ecotoxicology 03/2008; 17(2):69-81. · 2.36 Impact Factor
• Source

  Available from: briloon.org

  Article: Guidelines for Constructing and Deploying Common Loon Nesting Rafts

  Christopher R. DeSorbo, Jeff Fair, Kate Taylor, William Hanson, David C. Evers, Harry S. Vogel, John H. Cooley Jr
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  ABSTRACT: Artificial nesting islands, or rafts, are deployed in Gavia immer (Common Loon) territories to lessen the incidence of nest failures due to mammalian predation and water-level fluctuations. The effectiveness of this management tool has been demonstrated in other studies; however, improper construction and deployment can result in lowered nesting success. Despite widespread use of rafts, detailed construction plans and a protocol for deployment are lacking. We present the raft construction and deployment protocol currently followed by organizations specializing in loon management and research in New Hampshire and Maine, and discuss emerging concerns related to management using rafts.
  Northeastern Naturalist 02/2008; · 0.50 Impact Factor
• Article: Evers, D.C. Status assessment and conservation plan for the Common Loon in North America. U.S. Fish and Wildlife Service Tech. Rept. Hadley, Massachusetts. Mager, J.N., Walcott, C.W. and Evers, D.C. Macrogeographic changes in yodels related to body mass in the common loon. Waterbirds 30:64-72

  L. Savoy, C. R. DeSorbo, D. Yates, W. Hanson, K. M. Taylor, L. Siegel, J. H. Cooley, K. Munney, H. S. Vogel, N. Schoch, M. Pokras, W. Goodale