The changing natural world at our doorsteps | Illustration and text by Patterson Clark
November 15, 2011
For dark-eyed juncos, it’s “ladies first”
As days grow shorter and colder, dark-eyed juncos appear. Some will remain in the Washington area until after the cherry trees bloom.
Also known as snowbirds, the cold-loving sparrows are arriving from breeding grounds north of here. The species also breeds in the higher elevations of the Blue Ridge and in the mountains of West Virginia.
While Yankee juncos migrate south, mountain populations often simply fly downhill for the winter, where the climate is milder.
Leaving hubby with the kids, adult females tend to depart about two weeks earlier than males and juveniles, forming flocks that can be 80 percent female. Their head start results in winter populations that generally have a majority of females in southern flocks, and chiefly male flocks farther north and higher on the mountainsides.
Determining junco demographics at your bird feeder can be challenging: males and females look very similar. Juncos exhibit a wide range of variation in plumage, but males tend to have darker gray heads, while females sport more brown on their backs and wings.
SOURCES: The Condor, the Auk, USGS Breeding Bird Atlas, McGill Bird Observatory, www.ebird.org