Juncos

December 2009 - Bird of the Month

Get Ready for "Snowbirds"

Juncos and winter just seem to go together. Is it fate or an ancient rhythm of life that often brings the first snowfall and the first junco sighting at the same time each year?

Whatever the explanation, Dark-eyed Juncos are often called “Snowbirds” and many people believe their return from northern breeding grounds indeed foretells the return of winter’s cold and snowy weather. Even its white belly plumage and slate-colored back reminds one of a winter scene with its “leaden sky above and snow below.”

The Dark-eyed Junco is currently divided into six distinct populations that include the following: Oregon, Pink-sided, White-winged, Slate-colored, Gray-headed, and Red-backed Juncos. There are an additional 12 subspecies divided among these populations.

To avoid the competition, many female juncos migrate earlier and go farther south than most of the males. In Michigan only 20% of the wintering juncos are females, whereas in Alabama 72% were found to be female. Male juncos tend to spend the winter farther north in order to shorten their spring migration and thus gain the advantage of arriving first at prime breeding territories.

While almost all Slate-colored Juncos in the Eastern portion of North America migrate, a population of juncos in the Appalachian Mountains is residential, remaining in the same area year-round. Though the southward migration of Slate-colored Juncos is complete by early December, there is some evidence that indicates that harsh winter weather may spur some Juncos to move further south at anytime during the winter.

Juncos spend the entire winter in flocks that average in size from six to thirty or more birds. Visiting flocks of juncos will usually stay within an area of about 10 acres during their entire winter stay. They prefer to roost in evergreens at night, but will also use tall grasses and brush piles. They return to the same roost location repeatedly, sharing it with other flock mates, but they do not huddle together. Each winter flock of juncos has a dominance hierarchy with adult males at the top, then juvenile males, adult females and young females at the bottom. You can often observe individuals challenging the status of others with aggressive displays of lunges and tail flicking.

Watch for juncos feeding on the ground under your feeders this winter. Like many other members of the sparrow family, they are primarily ground feeders and are drawn to the millet and mixed seeds around the base of your feeders. Juncos are known to burrow through snow in search of seeds that have been covered over.

Dark-eyed Juncos tend to return to the same area each winter. Chances are that you have many of the same birds at your feeder this winter that you had in previous years.