Pigeons and house sparrows are perennial pests for some backyard bird feeders, but they don’t migrate and they don’t surprise. If you’ve got ‘em, you’ve got ‘em. They’re like feathered squirrels. For the rest of us, we welcome the chickadees, nuthatches, finches, titmice, cardinals, grosbeaks and woodpeckers, and rarely suffer the attention of less desirable species. Until the grackles show up.

Most have left by now. Around my house, I expect a huge flock around the time the leaves are falling. They persist a few weeks, and then they’re gone. For some, the invasion lasts longer. The bird feeders empty fast.

The common grackle is a native Maine breeding species, and it’s one hardy bird. Grackles are among the last birds to leave Maine in autumn, and the first to arrive in spring. Some don’t leave at all. On Jan, 2 this year, I encountered a flock of 80 during a Christmas Bird Count on Matinicus Island. Of course, they were hanging around the bird feeders of a year-round resident, poor chap. It’s hard enough getting a 40-pound bag of sunflower seeds out to an island 20 miles offshore without having to worry about grackles crowding out the other birds.

Grackles eat mostly seeds, even the toughest ones. They have a keel-like structure on the upper palate of their bills that enables them to crack acorns. They also forage on insects and spiders, as well as small aquatic critters like crustaceans and mollusks. They will follow farm plows to snap up whatever is panicked by the machinery, even mice. They will wade into shallow water and snatch minnows. They’ve been known to pick leeches off the legs of turtles. They will raid the nests of other birds.

But what they really like is corn. In much of North America, farmers consider them to be a bigger pest than crows. They breed in fields and wet meadows from the Atlantic to the Rockies, from the Canadian tundra to the Gulf of Mexico. In winter, grackles join with other species to form huge flocks, sometimes numbering over a million birds. Many of Maine’s grackles join these massive flocks that forage in warmer agricultural areas. Others winter in the salt marshes of the mid-Atlantic coast, where temperate breezes keep the wetlands ice-free, and the grasses and seed-bearing plants free of snow.

Many species gather in flocks. Our finches and waxwings do it. But finches and waxwings prefer a little solitude while nesting. Grackles don’t care. They nest colonially in close proximity to one another, defending only a tiny piece of territory around each pair’s nest.

Common grackles are noisy, but it could be worse. Boat-tailed grackles are noisier, and more prone to hanging around people. They are non-migratory denizens of the coastal plain in the southeastern United States. Great-tailed grackles are even larger, and even noisier. They are often found in western cities, where they have a penchant for sitting on downtown utility poles and raising a ruckus at sunset. In city parks, they are just as cozy around people as pigeons are, and just as numerous.

All male grackles are black, often shimmering with a purple iridescent head. Females are a dull brown. Common grackles have longer tails than other blackbirds. On boat-tailed grackles, the tail is even longer. On great-tailed grackles, the tail is so long that you wonder how the bird can avoid tipping over backwards. All grackles use their long tails in mating displays. They also fan them aggressively in the face of threats.

Many Mainers dislike grackles at the feeder because they aggressively shoulder aside other birds, and they can devour lots of seeds at an alarming rate. Fortunately, grackles prefer to forage on the ground, and not many can crowd around a hanging feeder. Their boisterous bullying mostly happens on platform feeders. Thus, homeowners can get some relief by taking down platform feeders while the grackles are present, and letting the blackbirds clean up underneath the hanging feeders until they are ready to move on.

If you’ve been plagued by grackles this autumn, you should soon be rid of them. Throughout the cold months, we will happily feed our resident chickadees, nuthatches, and finches. We will take great delight in feeding invaders from the north, like pine siskins, redpolls, and American tree sparrows. From now through March, it will be fun to feed the birds. Until the grackles show up again.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.