A Demographic and Landscape Analysis for Common Loons in Northwest Montana
Understanding the relationship between a species important vital rates and how they respond to environmental factors is essential for developing appropriate conservation strategies. Historically, breeding populations of common loons existed across much of the northwestern United States, but that area of distribution within the lower 48 states has been significantly reduced. Montana still has the largest breeding population of common loons in the western continental United States, averaging 40-70 territorial pairs annually. Most research to date on loon population dynamics, habitat use, and response to disturbance was conducted in much larger populations of the Midwest and Northeast United States and did not account for individual vital rate importance. Recent sensitivity analysis showed that fecundity was the vital rate had the most influence on the population growth rate in common loons. Therefore, I designed my research to evaluate the relationships between disturbance (as measured by the number of houses, resorts, and campgrounds in relation to lake size), habitat, intraspecific interactions and territory occupancy and reproduction. I used occupancy models to explore the dynamics underlying occupancy of potential lakes. I observed that landscape scale effects were important to occupancy of loon territories. The abundance of feeding lakes and the number of territorial pairs within 10 km were equally important for explaining probabilities of occupancy. I suggest managers protect both occupied, as well as, unoccupied lakes, especially when in close proximity to clusters of territorial pairs and feeding lakes. I observed that lake scale effects were more important to reproductive potential than landscape scale effects. I found a significant negative relationship with islands and a significant positive relationship with shoreline complexity on reproduction. Shoreline disturbance did not appear important when compared to other factors, but there are factors associated with Montanas outreach and education program that probably affected this result. For increasing reproduction I suggest managers continue current management activities, but include a greater focus on protecting nesting habitat on lakes without islands. I also suggest managers continue to mitigate for disturbance while exploring other ways to evaluate the effects of disturbance on occupancy and reproduction.
Advisor:Dr. David E. Naugle; Dr. L. Scott Mills; Dr. Michael S. Mitchell
School:The University of Montana
School Location:USA - Montana
Source Type:Master's Thesis
Date of Publication:05/06/2008