Monday, January 25, 2010

As the Crow Flies

Each afternoon during the winter, the crows begin their evening commute, heading home after their day’s work. Thousands on thousands make the trip, flying in small flocks or singly, their dark shapes contrasting sharply against the pewter-grey clouds of late January. The flight, which begins with just a few birds at mid-afternoon, quickly grows to form a steady stream of black glossy crows hastening to complete their journey before dark.

Their route is exactly opposite of that of their human counterparts, for the crows spend their days foraging in the suburbs and outlying agricultural areas, and roost in a large flock in downtown Hartford. In late afternoon the crows converge upon the city, coming from every direction to their central roost, while on the highways below, human commuters head out of Hartford back to their homes in the suburbs.

Crows roost communally only in the winter months; during the spring, summer, and autumn they are busy raising their young and tend to stay in small family units. For the past three years or so, a family of crows has made its home in our backyard. I can tell when the chicks have hatched, for at that point, an adult (I think it’s the mother) starts coming to our suet feeder regularly, taking chunks and flying off with them to the large trees at the back of the yard. A few weeks later, the young crows come too, parading around the yard while they take lessons in finding good things to eat. I can tell that it’s the same family because the mother has a crooked feather in her right wing. (I call her “Wingtip.”)

Our crow family has been around the yard this winter, too, eating suet as well as some meat scraps that I put out for them. They loved tearing apart the leftover Thanksgiving turkey carcass after I had cooked all its flavor into soup stock, and they picked up all the scraps of fat and rind from the ham I baked for the choir party.

Scientists have suggested several reasons why crows form large roosts in winter. Massing together helps to foil predators, of course, especially the owls that prey on the roosting crows at night. (The roost in Hartford has been estimated to be as large as 20,000 birds, though in recent years it has formed several smaller flocks of “only” about 6,000 birds in each group.) There is some evidence that crows cannot see well in the dark, so it’s possible that they make their night-time roost in the city where artificial lights are present. The urban environment is warmer than the outlying areas and has the added benefit of providing opportunities for the crows to socialize. And if you’ve ever heard a really large flock of crows “socializing,” you’ll agree that they love to chat.

Scientists also believe that the crows’ commuter lifestyle – fly to work in the suburbs and then fly home to the Hartford “bedroom community” – has supported a substantial increase in the crow population. The crows can easily fly 5, 10, or 15 miles each morning to reach their foraging areas: dumps, agricultural fields, commercial areas with restaurant waste, etc. If they roosted in the countryside, they would surely lose more of their numbers to natural predators, especially the younger, weaker birds that would be more vulnerable to predation. The greater safety of the communal city roost has led to increased survival rates and breeding opportunities.

On my own morning drive, I look for the crows, flying west from Hartford in groups of two and three, spreading out over the greater Hartford area for their day’s work. I see them around town during the day: the half dozen or so outside the high school; another half dozen at the library; a large flock of about 100 in the farm fields, and the little family of three or four in my own neighborhood.

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