We heard the “thunk” as something hit the window. “Honey, check outside, I think a bird hit the window again.” But by the time one of us got around to it, there was no sign of the supposedly stunned bird. Sometimes, though, we’d see a Cooper’s Hawk winging away. Only later would we learn that the Coop had actually chased a smaller bird into the window, then scooped up its stunned target. Ah! the ways of a smart predator.
Cooper’s Hawks are the common accipiter around the Columbus. Large and nimble, they are the terror of small birds in various park and suburban settings. Like most accipiters (a family of hawks specializes in pursuing birds), they have the lithe body, relatively short wings, and long thin tail that help them twist through trees and shrubbery while flying after a target bird. Unlike buteos that spend much of their time soaring, accipiters only occasionally soar, and it takes them some effort: their soaring is interrupted periodically by rapid wingbeats. Most often you’ll see them perched on a tree branch, their long thin tail hanging down well below their short wings.
Accipiters come in several species, but the only 2 we’re likely to see are Cooper’s and Sharp-shinned. Both were once forest birds, but the Cooper’s has adapted to the fragmented urban landscape and is now more common around Columbus than in nearby forested areas. Sharp-shins, however, are still largely forest birds and we most often see them in migration or winter. The Sharpie can be distinguished by its smaller size – some males can be barely bigger than a Blue Jay – and its shape. Its tail appears more square-ended when folded, while the Cooper’s tail is slightly rounded, and its head is smaller compared to its shoulders. Behavior is often a better marker: Sharpies have a faster wing beat, and sometimes shake their wings during flight to straighten out (the ‘Sharpie shake’). The smaller head is more noticeable in flight, but the tail squaring is less visible. Here is a good summary by National Audubon: https://www.audubon.org/news/a-beginners-guide-iding-coopers-and-sharp-shinned-hawks , but if you like video explanations, try https://www.youtube.com/watch?v=pOS_eRUbcTk
Both of these hawks are bird-hunters, the Sharpie tending to chase smaller birds like sparrows and warblers, while the Cooper’s targets slightly larger prey like Robins, Cardinals, and doves. Their classic hunting stratagem is to wait on a concealed perch and dash out to chase passing birds. Suburban Cooper’s hawks have altered this to wait near a feeder or a farm feedlot, then dash out to chase the scattering feeder birds. So successful is this new strategy that Cooper’s Hawks are now the most common hawk in most urban/suburban areas and even overwinter in these areas as far north as Toronto. Most of these changes are nicely summarized here: https://thousandislandslife.com/probably-good-news-coopers-hawk/ Sharpies are also learning this trick, and we’ve been seeing more of them around suburban yards in recent winters.
Accipiters have an instinct to kill – they grab their prey with their talons and break its spine with their beak – but they have to learn to hunt, and the learning curve is long and hard. It’s estimated that 50-80% of young accipiters perish in their first year. Young accipiters can be recognized by their streaked breasts (adults have orange barring instead), and you’ll see a lot of them in fall and winter. Not only are they less adept at concealing themselves on perches, but they often are flying around scouting hunting locations. I recently watched one flying around a yard and sitting in the grass, something an adult probably wouldn’t do. One amusing feature is that groups of crows will often playfully taunt young accipiters. You can often locate one by listening to the cawing crows and watching as they joust with the young hawk. These play battles might actually help both crows and hawk learn the ropes about escaping and chasing. You can watch a trio of juvenile Cooper’s Hawks pester a flock of crows here: https://www.youtube.com/watch?v=gOticlCk5OY . If the hawks survive to adult-hood, learning effective ways to hunt and chase, the crows won’t be as eager to play with them.