Winter Weight Gain or Breeding Activity Weight Loss : How Does Dark-Eyed Junco Weight Seasonally Differ?

Abstract

Dark-eyed Juncos of the Slate-colored subspecies (SCJU) are boreal migrants that over winter in lower latitudes, such as Wisconsin. In the spring, Juncos migrate to northern breeding grounds. The purpose of this research is to determine whether there is a weight difference between pre-breeding (March- May) and post-breeding (September- November) Juncos banded at Beaver Creek Reserve (BCR), Fall Creek, WI. Fat accumulates in the furculum on the birds and is visible to the naked eye. We used data collected from the Bird Banding Program (2007-2016).