By PAUL HETZLER

Eat your hearts out, synchronized swimmers—blackbird migration is underway.

With all due respect to those highly choreographed aquatic athletes, a flock of thousands of blackbirds diving and wheeling in unison is even more impressive. Although grackles, cowbirds and the invasive starlings are usually lumped into the category of “blackbird,” it’s our native red-winged blackbird that I more often see.

Considering that red-wing blackbirds are the most numerous bird species in North America, why is it that their migration so often escapes our notice? After all, their flocks are much larger, in terms of numbers, than those of geese. In fact, Richard A. Dolbeer of the USDA-APHIS Wildlife Services in Denver says that a single flock may contain over a million birds.

Canada geese migration is hard to miss. Even if their V-shaped flocks don’t catch your eye, their loud honking will let you know what’s up, so to speak. But blackbirds are smaller, and migrate primarily at night, and their voices don’t carry as far. And admittedly they aren’t as numerous in northern New York as they are in the upper Midwest.

All blackbirds, red-wings included, are omnivores. They feed on insect pests such as corn earworms, as well as on weed seeds, facts which should endear them to us. Unfortunately they sometimes eat grain, which does the opposite. They rarely cause significant damage to crops.

Along with robins, they’re one of the first signs of spring. Usually I hear the males’ “oak-a-chee” call, which is music to my ears, before I see them. And the red-and-yellow wing patches, or “epaulets,” of the males are a welcome splash of color in mid-March.

Red-wings often nest in loose colonies in marshes. I recall canoeing with my young daughter through cattails and peering into red-wing blackbird nests. Marshes afford them some protection from predators like foxes and raccoons, and the females, which are a mottled brown color, blend in well. Hawks, and owls to a lesser extent, take a toll on blackbirds regardless of where they nest, though.

In the fall, blackbirds flock together before migrating to locations in the southern US. This is when they display their acrobatics. Perhaps you’ve driven along great undulating flocks of blackbirds and marveled at the way they’re able to all change course instantly.

One morning this fall a great number of red-wings landed in a large sugar maple in my yard. I watched in awe as they streamed up out of that tree and poured themselves back down into another large maple nearby. They repeated this “avian hourglass” performance several times.

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. (Movie animators have used these algorithms to depict movements of fish and herd animals.)

Apparently, each bird keeps track of its six (I’d like to know how scientists arrived at this number) closest neighbors, 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. This suggests birds are smarter than drivers on the Long Island Expressway, who reportedly smack into other migrating cars on a routine basis.

But exactly 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 a study of flocking starlings in Rome, “The exact way it works no one knows.” Don’t you just love an honest researcher?

Well I’m off to try and find the whereabouts of my six closest neighbors.

Paul Hetzler is a forester and Cornell Cooperative Extension of St. Lawrence County horticulture and natural resources educator.