First, you'll only see one flock at a time. Winter flocks defend feeding territories -- they don't tolerate intrusions from other flocks, unless it gets really cold and snowy. I've counted as many as 47 juncos beneath my feeders during a snowstorm.
Second, within a flock there is a definite social hierarchy or pecking order. Adult males occupy the top rung of the social ladder, followed by young males, adult females, and finally, young females. Dominant individuals eat first. Lower ranking juncos wait their turn. Early in the morning and late in the day, when feeding is most intense, you're most likely to observe aggression between dominant and subordinate individuals. Dominance is probably determined by a combination of age, gender, and experience.
When juncos head north in April, their instincts shift from winter survival to reproduction. Longer days trigger hormonal changes in males that induce them to sing a musical trill from the tops of the tallest trees. The monotone song is easy to recognize, though it might be confused with a chipping sparrow's song. Parallel hormonal changes in females make the males' song attractive, and pairing occurs.
Though males help gather nesting material, the female builds the nest alone. It's usually on the ground hidden under roots, a log, a rocky ledge, or an overhanging bank along a stream or road. The female lays four or five eggs and incubates them for about 12 days.
Thanks to fast-growing feet and legs, nestlings can leave the nest on foot when danger threatens as soon as nine days after hatching. Normally they begin to fly at 12 to 13 days. After the nesting season, which may include two broods, shorter days and plunging temperatures send them back to us for the winter.
The calendar may tell us winter's still weeks away, but the juncos are reminding us to keep the snow shovel handy.
For more information about juncos and a terrific new movie, "Ordinary Extraordinary Junco," visit www.juncoproject.org. The download is free.