Common Loon nesting ecology in Northwest Montana

Abstract

Common Loons (Gavia immer) are found across the northern continental United States and in Canada and Alaska. The common loon is long lived, with delayed breeding maturity and low fecundity. Surveys indicate Montana's Common Loon population remains stable, but lakeshore development and watercraft recreation are increasing. While the effects of these changes are unclear, research investigating reproductive success over a gradient of habitat conditions, at multiple spatial scales is lacking. The objectives of this research were to investigate vital rates and the relationships between daily nest survival, chick survival and environmental covariates across multiple spatial scales. I monitored seventy-nine Common Loon nesting attempts and the fates of sixty-five Common Loon chicks during two field seasons in Montana. The strongest predictor of nest survival was the type of breeding territory occupied by loons. Loon nests on small lakes (<60 acres) showed the highest nest survival, followed by nests established on large lakes (>60 acres) occupied by a single breeding pair. The lowest nest survival occurred on large lakes (>60 acres) occupied by two or more breeding pairs.

I found effects of landscape and lake scale covariates on chick survival, where chick survival was positively related to the number of foraging lakes, and number of adjacent pairs, within a 10-km radius of the nest. I observed a negative association between recreation activity and chick survival. Management actions designed to affect nest survival must vary depending on the type of nesting territory targeted. Management priorities for all territory types should focus on maintaining and restoring shoreline and island nesting habitat, and modifying watercraft recreation during the nesting period. Because small nesting lakes were the most productive, MLT areas should receive the highest attention. Land use planners involved with MLT lakes should consider minimizing watercraft disturbance on adjacent lakes to maintain, or improve, adult foraging habitats. Finally, efforts to increase chick survival need to focus on minimizing the negative effects of human recreation, especially during the first week post-hatching. Temporary "no wake" restrictions, or using floating signs to eliminate watercraft use in historical chick nursery areas, may increase chick survival.