There are flocks of red-winged blackbirds and of starlings drifting about the countryside. Without apparent formation, they appear to be masses of black birds from a distance, loose balls of birds. The redwings often drop into standing corn, much to the displeasure of the farmer whose corn it is. The starlings often settle in mowed fields and in pastures where they scuttle about catching grasshoppers and other insects.
Barn swallows and tree swallows, bank and rough-winged and cliff swallows fly about, all across the sky without any semblance of flocks. But when they land they land together, on an electric power line, sometimes on the branches of a standing dead tree.
I go walking through a woods, in the nearby park or in a Land Trust nature preserve, and hope to find robins, a flock of them. They’ll be in the trees, on the ground, on the path ahead. They’ll be flying from the trees to the ground, from the ground to the trees. They’ll be calling but not singing, chirps all around and I’ll hear many more than I’ll see.
This is a time of birds in flocks. Their nesting time is over, all but the last, late nesting goldfinches and a few mourning doves with fourth or even fifth broods. As their nesting ended one brood, one family of geese or redwings, starlings or robins, joined another and another and another. Flocks of many birds have formed and become larger and larger and the flocks continue to grow.
Nearly everyone must have seen flocks of Canada geese and red-winged blackbirds, starlings and robins when the robins have ventured out of the woods and spread across a grassy park or lawn. Did you ever wonder why birds settle in one field, or woods, and not another? Why do many flocks fly into one area at dusk and roost together, then spread out in flocks again when they leave the roost at dawn?
For three years as a graduate college student I studied red-winged blackbirds. In spring and summer I observed their territorial behavior, mating and nesting, then in late summer and fall I observed flock formation, followed flocks and noted their movements and feeding and coming together and roosting at night.
After three years of studying red-winged blackbirds, watching them, following them daily, I still can’t tell you if they have a leader of a flock. I can’t tell why they fly over many fields of corn before landing in one. I can tell you that they roosted most often in the cattails of marshes but I can’t tell why they roosted in one marsh and not another. Nor can I tell you why they were segregated by sex, males roosting in one marsh, females in another. That’s a peculiarity of red-winged blackbirds and a few other species.
I can’t answer those questions for other birds either. It appears that Canada geese have a leader, the bird at the head of the V or line when they fly but watch for a time and you will see that the leader changes. The second bird on one side of the V or in line will replace the first after a time. There will be no change in direction of flight or altitude or speed, but even lack of change raises questions when bird flock watching.