For the birds
Teachers, cat-herders, and others, whose job is to maintain order in the midst of chaos, must wonder how Canada geese organize their youngsters into neat formations without evident squabbling. Yet discipline among a cloud of ten thousand blackbirds, who turn, wheel, and dive in unison without crashing into each other, eclipses the order found in the tidiest geese chevron or the sternest classroom.
Considering that red-winged blackbirds are the most numerous bird species in North America and that their flocks can contain up to a million birds, their migration still often escapes our notice. While Canada geese migration is hard to miss, blackbirds migrate mostly at night and they don’t announce themselves the way that geese do.
Like all blackbirds, red-wings are omnivores. They feed on insect pests such as corn earworms, as well as on weed seeds, which should endear them to us. Unfortunately they also eat grain, which has the opposite effect, even though studies indicate they seldom cause major crop damage.
Along with robins, they’re one of the first signs of spring. Usually I hear before I see them; the males’ “oak-a-chee” call is music to my ears in more ways than one. And the red and yellow wing patches, or epaulets, of the males are a welcome splash of colour in the sepia-and-snow tones of mid-March.
Red-wings often nest in loose colonies in marshes. I recall canoeing with my young daughter through cattails, peering into red-wing blackbird nests, while adults hovered overhead, objecting loudly, and sometimes diving a bit too close to our heads. Marshes afford red-wings some protection from predators like foxes and raccoons, and the females, which are a mottled brown, blend in well. Hawks, and owls to a lesser extent, take a toll on blackbirds regardless of where they nest, though.
Down in the St. Lawrence Valley, you can see great undulating flocks of blackbirds at this time of year, as they gather before migrating to locations in the southern U.S. It’s marvelous the way they can all change course instantly. Researchers have long puzzled over synchronized flock movement. In recent years they’ve made some progress thanks to high-speed imaging, algorithms, and computer modeling. In fact, movie animators have used biologists’ algorithms to better depict movements of fish and herd animals.
Apparently each bird keeps track of its six – no more, no fewer – closest neighbours, and coordinates its movements with them. No matter how many times they turn or dive, they maintain about the same distance between themselves and the six closest birds.
But precisely how do birds maintain distances within a flock or know when to change course? In the words of Claudio Carere, an Italian ornithologist deeply involved in studying the behaviour of starling flocks in Rome, “The exact way it works, no one knows.” I like an honest researcher.
Paul Hetzler is a former Cornell Extension Educator, and a failed cat herder who lives in Val-des-Monts.