Nantucket, MA

BIRDS OF NANTUCKET THE BROAD-WINGED HAWK by Kenneth Turner Blackshaw Afew weeks ago these birds were high in the air over Veracruz, Mexico, circling in a stream with thousands of their own kind, lifted by invisible (to humans) thermal columns of air. Swirling flocks like this are known as "kettles," because their roiling motion is like water in a pot at a full boil. Broad-winged Hawk At this point they were about half way through their 4,000-mile migration route from South America to the U.S. and Canada. Their migration is rather leisurely by bird standards, averaging 70 miles a day. During peak times as many as 58,000 may be seen winging over the Veracruz "hawkwatch" site and a few autumns ago it was estimated that 2 million birds went by. We are talking about a small buteo hawk called the Broad-winged Hawk. Buteos are a class of hawk with rounded wings and tail. Nantucket's Red-tailed Hawks are also buteos but much larger. Europeans refer to buteos as "buzzards," hence the name Buzzard's Bay doesn't refer to vultures but rather to the Ospreys that ply those waters looking for fish. Ospreys are not buteos but were close enough to be tagged that way by early settlers. The Broad-wing's scientific name is Buteo platypterus, translating to broad-winged hawk. Using the birding yardstick of 20 inches for a crow, Red-tails appear bigger and Broad-wings a bit smaller. The main field mark for the Broad-wing is the strikingly banded black and white tail. Only the Red-shouldered Hawk, rare here, has a similar tail pattern but its bands are smaller and more tightly distributed. Broad-wing tail bands are quite broad, particularly the final black one. This column's illustration looks down on the hawk from above. When seen from below the underwings are very pale with a fine black border. Since Broad-wings don't nest here they must be off-course when they reach Nantucket. Like most birds that use warm thermal currents to lift them high in the air, they try to avoid flying over water, particularly cold water. There's no lift for them there. When they stray to Nantucket it is a big treat for us. Just a few springs ago the Sunday morning bird watchers were beside Miacomet Pond when suddenly a single Broad-wing was spotted circling into the heights to the east. It was quickly joined by its partner and the group had a marvelous time watching them climb higher and higher, slowly heading to the west. You could clearly see the size difference suggesting these birds were paired off. In birds of prey, the female is much larger than her mate. Broad-wings nest over most of Massachusetts including Cape Cod, but it's felt they require more substantial trees and larger hardwood forested areas than we find on the Vineyard or here. They are true forest dwelling hawks and often hunt from a tree perch rather than soaring in the air. Given this, they are not often seen unless seduced by a rising thermal current during migration. Broad-wings usually build a new nest every year unlike Red-tailed Hawks that frequently keep adding to the same foundation. They also don't return to a particular territory more than a few years before heading to another. The nest is usually 25 to 40 feet up and often decorated with sprays of greenery or even flowers. The most common number of eggs is two and apparently Broad-wings are very trusting of humans around their nests. Audubon reported one of its artists carried a nesting Broad-wing down to the ground after placing a handkerchief over its head. After he drew it he replaced the trusting, or perhaps really stupid, hawk back in her home. This trust of humans is in spite of the horrific hawk hunting that went on in the early part of the 20th century. In 1925 a huge Broad-wing flight went through Minnesota. The comment was, "this brought out just about every man who owned a gun and they blazed away, killing thousands." Of course this was because at that time every hawk was considered to be a "chicken hawk" and therefore deserving of killing. Strangely enough, a Broad-winged Hawk's favorite food seems to be toads. If they are in an area where toads are spawning, their diet contains little else. They also eat a lot of insects, small mammals, and snakes. A small hawk like a Broad-wing would seldom hit something as large as a chicken but that didn't matter to the men who felt they had to shoot them. Since Broad-wings are true neotropical migrants, it is very rare to find one in our climes after the end of September or before mid-April. On Nantucket we don't expect them in the autumn at all but from the end of April until mid-June it's possible to find them soaring in our skies like they did over Miacomet a few springs ago. In the fall, Broad-wings form a river of hawks leading to the aerial channel through Texas and then along the western shores of the Gulf of Mexico into Central and South America. Now in the spring they are reversing the process. As I mentioned in the beginning, the ones we may see now have just passed through the neck of the funnel in Mexico heading north before exploring our skies. I George C. West creates illustrations for these articles. If you enjoy 'social' birding, join the Nantucket Bird Club at 8 a.m. Sundays in front of Nantucket High School for a two to three hour birding trip. Call 228-1693 for more information. To hear about rare birds, or to leave a bird report call the Massachusetts Audubon hot line at 1-781- 259-8805. Find more about Birding Nantucket on the web at http://k-blackshaw.com/BN/BN.htm.