Banding Wrapped Up for the Year

Two nights ago we completed our last night of loon capture and marking for the 2013 season. It was a banner year, as we banded 87 chicks, 26 unbanded adults, and made 56 recaptures of adults banded previously. (We broke our 2005 record for chicks banded by 20!) Of the recaps, 10 males and 3 females were birds we (or Mike Meyer of the Wisconsin DNR, in the case of 2 of the females) had marked as chicks but never caught as adults. Weighing of these birds contributes vital data to our analysis of changes in body condition that occur with age among young adults and have provided further evidence that loons — at least males — do improve in body condition from ages 4 to 10 years. This is an important finding, as it runs parallel to the clear behavioral finding that young adults improve in competitive ability during this phase of life. That is to say, young adults are in better condition (measured by body mass) at ages 7-10, when they usually usurp territories from established breeders, than ages 4-6, at which time they choose to found new territories in vacant lakes (without having to fight for them). This is a neat and intuitive result that I am currently writing up for publication.

The abundance of chicks banded this year will allow us to enlarge upon our investigation of natal site matching (based on our recent paper) that we began last fall. Kristin and Gabby from this year’s team will spend this fall tracking the chicks as they mature, begin to fly and disperse to lakes nearby their natal one. Our goal here is to determine whether young loons “imprint” on lakes similar to their natal lakes in the first few months of life. If so, chicks hatched and reared on small lakes — which, as we have recently shown, tend to settle to breed on small lakes — might choose to visit small lakes when flight allows them to do so to feed, while chicks from large lakes should select other large lakes for foraging. Stay tuned for the outcome of this autumn investigation!