Most territorial pairs of loons in our study area — central Oneida County, Wisconsin — are marked with colored leg bands for individual identification. Many “floaters” (young adults that have not yet settled on territories) also have colored bands on their legs, because we marked them as chicks on their natal lakes. The marked population extends northwards to the border of the Upper Peninsula, because the Wisconsin DNR has marked many pairs in Vilas, Forest and Iron counties of Wisconsin.
Marking of animals is essential for studying population and behavioral ecology, especially when, as in loons, individual animals are not readily distinguished by size, behavior or external markings. By placing color bands on loons, we are able to learn when and how they gain and lose territories and to track population dynamics. Recently, analyses of marked loons permitted us to estimate annual survival rates in established breeders on territories as well as juveniles, which made it possible to examine population trends. Having loons banded over a large continuous area also allows us to learn about dispersal patterns — that is, how far loons move from hatching lake to breeding lake and between breeding lakes.
The colored leg bands that we use do not impair swimming or any other aspect of behavior that we have measured. In fact, loons entirely ignore their bands, even during preening. Yet the presence of bands permits us to track identities of individuals within and between territories, across years and from chick to adult.
Leg bands are visible during a variety of normal loon behaviors, such as swimming and preening. As you can see from the video below, it is sometimes possible to view both bands on a leg while a loon is resting or diving. This female is “white over white” on the left leg.
With good light and tame birds, one can often observe both bands on a leg while loons are swimming along the surface of a lake. Here, “red over blue” bands on one loon’s left leg can be seen, as well as the “green over green” bands of its mate, despite early morning light.
The easiest time to identify marked loons from their bands, however, is when they preen. Here, a tame loon rolls on its right side to preen, holding its left leg up in the air and then does the reverse, showing its right leg. This individual is “silver over green on right, white over orange on left” or “S/G,W/O”.