Local Movements of Color-Marked Common Loons

We studied movement of color-marked common loons (Gavia immer) among small lakes (4-349 ha) in northern Wisconsin and the Upper Peninsula of Michigan to determine the frequency, timing, and ecological causes of multiple-lake usage. Most instances of multiple-lake usage fell into 1 of 5 categories: (1) territorial defense of 2 or more lakes by a breeding pair, (2) post-reproductive wandering, (3) territorial shifts prior to breeding, (4) dispersal of displaced breeders, or (5) long-distance movements by young birds. Overall, distances moved by adult loons between lakes were shorter than expected. The frequency of such movements might indicate reconnaissance for new territories, consistent with the frequent territorial takeover observed in this species. Regular use by loons of small clusters of lakes suggests that a management strategy that preserves only small, isolated breeding lakes might be inadequate to sustain nesting pairs and also might hamper natural dispersal between lakes.