October is a time when we can expect to see large flocks of Dark-eyed Juncos. The ivory-colored bill is a good field mark. Adult males have gray above, extending down onto the throat and upper breast. The gray contrasts with the white lower parts of the underside. Females are brown above with some muted gray feathering as well. In both sexes, the outer tail feathers are white, flashing a warning when a bird suddenly takes flight.
Although these sparrows can be found year-round in Maine, their numbers are bolstered in our state by passage migrants (migrants simply moving through Maine) in April en route to more northerly breeding grounds and in October en route to more southerly wintering areas.
Dark-eyed Juncos breed from northern York County northward throughout the rest of the state. Breeding densities are greatest in the spruce-fir forests of the northern half of Maine. Some juncos overwinter but their numbers vary from year to year.
The entire geographic range of Dark-eyed Juncos is huge, extending as far north as the tree line in Alaska and Canada and southward throughout most of the lower Forty-eight, excepting peninsular Florida. Some even winter in northern Mexico. A recent estimate placed the Dark-eyed Junco population at around 630 million birds.
This broad range means that most North Americans see juncos during some portion of the year. The confiding nature of these birds and their willing use of human-altered landscapes increase the likelihood of our encountering these birds. John James Audubon in 1831wrote that “there is not an individual in the Union who does not know the little Snow-bird”. Growing up in North Carolina, I heard these birds referred to as snowbirds as well. Their arrival in the South coincided with the onset of winter.
Junco is the genus of these birds as well as the common name. The name seems ill chosen because Junco is derived from Juncus, an emergent reed growing on the margins of lakes and ponds. Hardly the habitat of a junco.
Juncos feed primarily on the ground and from the leaf litter. Seeds as well as insects and other arthropods like spiders make up the bulk of the diet of Dark-eyed Juncos. They will occasionally take fruit. Diet studies show the juncos prefer small seeds. Important seeds taken include those from chickweed, pigweed, knotweed, sorrel and timothy grass.
Although juncos spend a lot of time on the ground, I often find male juncos singing their hearts out at the top of a tall spruce or fir. Their trilled song is easily confused with other trillers, particularly the Chipping Sparrow. The junco song is more musical and bell-like to my ear.
Males are strongly territorial during the breeding season, defending a territory of about three or four acres. In winter flocks, a strict hierarchy or pecking order is set up. Every junco knows her or his place in the power structure of the flock.
Dark-eyed Juncos have been the course of much debate among bird taxonomists. Until 1973, the currently recognized Dark-eyed Junco was split into five species, each with some distinctive feature on top of the generalized junco morphology. In the east, we had the Slate-colored Junco and the other species were White-winged Junco, Oregon Junco, Gray-headed Junco and Guadalupe Junco. Based on the joint possession of dark eyes and other anatomical considerations, the Check-list Committee of the American Ornithologist Union merged these five species into a single species. This decision is disputed by some bird systematists. Recent fieldwork shows that different junco forms at abutting geographic boundaries do not freely interbreed. This evidence may be sufficient to restore species status for some of these forms.
I remember the frustration of many competitive North American birders at the decision to lump the five species of juncos into one. These listers saw their life lists decrease by four species!
[Originally published on October 12, 2014]