Friends with bird feeders have told me that they’ve sometimes seen a hawk diving past their window toward their bird feeder.
“It’s usually a Cooper’s hawk at bird feeders, especially in winter,” said Wayne Petersen, director of Mass Audubon’s Important Bird Areas program. “People who have bird feeders know them.”
But the hawks aren’t looking for birdseed. They’re hunting other birds.
“We see them fairly frequently,” Ranee Duncan of Westborough said in an e-mail. “One took out a bird while we were having a family BBQ on our deck, right next to the feeders. A puff of feathers descended upon us!”
The range of the Cooper’s hawk extends across the continental United States and southern Canada, according to the Cornell Lab of Ornithology website. While most Cooper’s hawks migrate south for the winter, Petersen said, increasing numbers are choosing to overwinter in Massachusetts.
“An increase in bird feeding through the years matched the increase in overwintering Cooper’s hawks,” said Petersen. “They make a living at bird feeders.”
The Cooper’s hawk was named for 19th-century American naturalist William Cooper, according to Paul Roberts, founder of Eastern Massachusetts Hawk Watch.
Cooper’s hawks reached their peak of abundance in Massachusetts in the late 1800s, but began to decline after 1900 due to conflicts with people, according to Mass Audubon’s website.
“They were never beloved because they ate small birds and chickens,” said Petersen. “They were significantly persecuted and illegally shot.”
Habitat destruction and pesticides added to the hawk’s problems, according to Mass Audubon, and by the 1970s, the Cooper’s hawk was a rare breeder in Massachusetts.
Over time, persecution of Cooper’s hawks decreased, Petersen explained, and they’ve rebounded in the past several decades. They are also a forest and forest edge bird, and as forests have grown back in Massachusetts, so have the hawks’ numbers.
Once thought to be averse to cities and towns, Cooper’s hawks are now fairly common urban and suburban birds, according to the Cornell Lab.
“They could be the second most common hawk in Massachusetts after red-tailed hawks,” said Petersen.
Cooper’s, like red-tails, are now nesting in almost every town and city in the Commonwealth, according to Roberts.
“Everyone who has multiple bird feeding stations or lives near a commercial area that supports an active pigeon population sees lots of Cooper’s hawks, especially in winter,” said Roberts.
“Although ‘Cooper’s are courageous’ — not shy about perching in public and being observed by people — people are still much more likely to see a red-tail than a Cooper’s. Red-tails are bigger, soar more, and perch in the open more, and are more familiar to non-birders.”
Cooper’s hawks are sneaky, said Petersen. “They tend to sit in the middle of a tree. They usually hunt from a perch. They take off like a missile when they go after a bird.”
Cooper’s hawks have long tails that act like rudders, said Petersen, and rounded wings that are good for maneuvering in flight.
The Cornell Lab said Cooper’s hawks are “among the bird world’s most skillful fliers” and they “tear through cluttered tree canopies in high-speed pursuit of other birds.”
Even though Cooper’s hawks are able to maneuver deftly while chasing birds, they are not immune from accidents.
Dr. Maureen Murray, director of the Tufts Wildlife Clinic at the Cummings Veterinary Medical Center at Tufts University, said in an e-mail that Cooper’s hawks are the third most common bird of prey they see at the clinic, behind red-tailed hawks and barred owls.
“At Tufts Wildlife Clinic, we admit from 40 to almost 60 Cooper’s hawks per year,” said Murray. “The majority of these birds have traumatic injuries. One of the most common causes of these injuries is the bird flying into a window or glass door due to the reflection appearing like open space rather than a physical barrier. Windows are a hazard for all birds, and Cooper’s hawks are chasing other birds. These types of collisions can cause fractures, as well as head and eye injuries.”
In spring, migratory Cooper’s hawks typically arrive from late March into April, said Petersen.
A clutch of four to five eggs is laid from late March to early June, according to Mass Audubon, and the eggs typically hatch after a few weeks.
Although Cooper’s hawks feed primarily on medium-sized birds throughout most of the year, when nesting they tend to take a lot of chipmunks, said Petersen, probably because there’s more meat to feed the hawks’ chicks. Chicks fledge when they’re about a month old.
Cooper’s hawks grow to about 16.5 inches in length and have a wingspan of up to 31 inches, said Petersen. Females are larger than males.
Adult Cooper’s hawks are bluish-gray on the back, and rusty colored on the front, said Petersen. Young Cooper’s hawks are brown on the back, with streaks of brown on their upper breast. It takes a couple years for the young hawks to develop adult colors.
The smaller sharp-shinned hawk, which looks very similar to Cooper’s hawks, will sometimes hunt at bird feeders, too, said Petersen. “Cooper’s hawks have bigger, more rounded tails,” said Petersen. “They also have longer necks and bigger heads. Sharp-shinned hawks’ heads look like a little peanut out in front of the wings.”
But the Cooper’s hawks’ mini-me has reason to be wary of its larger relative.
“Cooper’s eat smaller hawks and owls,” said Roberts. “Sharpies are shy. They are much more reluctant to perch in the open and be seen than are Cooper’s, because they feel vulnerable to larger predators. You might see both work an area of feeders, but I know who I’d bet on.”
Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to email@example.com.