Thursday, July 18, 2024

A broad-winged hawk at Mount Watatic on Sept. 19, 2021. (Photo: Brian Rusnica)

Red-tailed hawks are relatively common and well-known in the city. But you might see thousands of a different kind of hawk – a broad-winged hawk – in a single day if you look in the right place. In the fall, broad-winged hawks migrate through our region to Central or South America. They do this during a narrow window of time from Sept. 10 to Sept. 26.

Broad-winged hawks live in forested areas, so they do not breed in cities. They spend their summers in wooded areas of Massachusetts as well as northern New England and Canada. Unlike red-tailed hawks, which migrate singly if at all, broad-winged hawks migrate in huge flocks that can number in the thousands.

A broad-winged hawk eats a rodent on May 10, 2020. (Photo: Tom Murray)

Some of the best places to view the fall migration of broad-winged hawks are Mount Wachusett in Princeton and Mount Watatic in Ashburnham, but you can see the broad-winged hawk migration locally if you look in the right place. According to Brian Rusnica, president of Eastern Massachusetts Hawk Watch, those places include the hill on the southern end of Fresh Pond, the tower at Mount Auburn Cemetery, Pinnacle Rock in the Fells, Great Meadows National Wildlife Refuge, Dunback Meadow in Lexington or anyplace that gives you an expansive view of the northern horizon.

According to Rusnica, last September, hawk watchers saw 60 broad-winged hawks in a single day at Pinnacle Rock. Then Sept. 19-20 were rainy, foggy days when hawks prefer not to migrate. So on Sept. 21, there was an enormous burst of activity – hawk watchers counted 7,918 at Mount Wachusett! Rusnica says that hawk watchers get really good at counting, but if they miscount at all, they undercount the total number of hawks. One can only imagine how full the skies were that day.

A broad-winged hawk with tattered feathers flies over Groton near the end of its long spring migration north. (Photo: Tom Murray)

Broad-winged hawks use the length of daylight to signal when it is time to migrate. They wait for clear days with a 10 to 20 mph wind out of the north. Then they follow the trail of thermal updrafts along the Appalachians to move southbound. The thermal updrafts are like elevators that carry the hawks upward 2,000 to 3,000 feet; then the hawks glide down to find the next updraft. Hawks use 30 percent more energy flapping than gliding, so it is to their advantage to glide as much as possible on their protracted 4,000-mile journey south. Broad-winged hawks don’t eat much during their migration, so conserving energy is important.

Broad-winged hawks circle in large flocks called kettles as they gain altitude in the thermals. (Flocks are called kettles because the birds look similar to bubbles swirling upward in a kettle.) Once the hawks reach the top of the thermal, they break off from the flock and glide downward, flapping as little as possible. In this manner, they can travel 300 miles in one day. According to Rusnica, last year, a tagged hawk from New Hampshire traveled to Colombia in 37 days.

A kettle of broad-winged hawks circles in a thermal to gain altitude near Mount Watatic in Ashburnham on Sept. 17, 2015. (Photo: Brian Rusnica)

The Appalachians peter out in Alabama, but surprisingly the hawks pick up speed there. This occurs because the thermal updrafts in flat states can extend upward to 10,000 feet, so the hawks can glide down much farther.

Broad-winged hawks breed in Canada, New England, and yes, Massachusetts. They are reclusive, however, and prefer densely forested areas, where they can hide and perch on the forest edge to look for prey. Because these hawks are smaller than red-tailed hawks, the prey they prefer is smaller, too: chipmunks, mice, voles, nestling birds, some frogs, toads and snakes. Many of these critters are not around in the winter, so the hawks migrate south where they can overwinter in better hunting grounds. They return north mostly in April.

A broad-winged hawk surveys the scene in Groton on May 10, 2020. (Photo: Tom Murray)

Broad-winged hawks use landmarks to guide them on their migrations. They follow the peaks of the Appalachians and then fly southwest, skirting the Gulf of Mexico. By the time they reach their southern destination, they may have traveled 4,350 miles or more. After they arrive, each hawk tends to stay in a one-square-mile area, where it can focus on hunting rather than traveling.

Unlike many other hawks, broad-winged hawks are declining in numbers. This may be due to shooting and pesticide use in their overwintering areas. Of course, the wildfires in Canadian forests this summer have probably not helped.

A juvenile broad-winged hawk glides over Mount Watatic on Sept. 11, 2022. (Photo: Brian Rusnica)

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Reader photo

Candy and Randy send us this photo of orioles in July at their very busy bird feeder.

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Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.