Why do we routinely capture and mark loons for our study? Unless we gain a substantial amount of information from such efforts, one could argue that the disturbance we cause to loons by marking them is unjustified.
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 track them throughout their long lives, learn when and how they gain and lose territories, and monitor 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 how far they move from one breeding lake to another, in the event they are evicted from a territory.
We use twenty-three different color patterns on our loon bands, as shown here:
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”.
As suggested by the videos above, the colored leg bands that we use on loons do not impair swimming or any other aspect of behavior that we have measured. Although it is common for some species of birds to pick at their leg bands and try to remove them, we have never observed loons to act this way. In short, loons wholly ignore their colored leg bands.