Some truths about the true hawks

By BILL CHAISSON
Of a Feather
There you are, sitting peacefully in your armchair, watching the birds at your feeder as they quarrel among themselves, crack open sunflower seeds, and generally go about their business. Suddenly a streak of gray, brown, and white flashes past and one of the goldfinches disappears in a flutter of feathers. You have just witnessed a link closing in the food chain.

Accipiters are called the “true hawks.” They have relatively short, rounded wings and relatively long tails. Both of these features equip them for flying rapidly through the trunks and branches of their forest habitat as they pursue their prey on the wing. When you see an accipiter crossing an open area or in migration, they can be identified by their distinctive flight pattern of several rapid wing beats and then a short glide. If falcons are designed for something like NASCAR racing, lots of long straightaways, then accipiters are designed for something more like Grand Prix racing, all cornering and maneuvering.

We have three species in New Hampshire (and the same three are found across North America), from smallest to largest: the sharp-shinned, the Cooper’s, and the goshawk. The sharp-shinned and the Cooper’s hawks are similar looking. The adults have slate-gray heads, backs and tails, and their chests and bellies are crossed by fine rufous barring. Their undertail coverts are white and the tails have dark gray bands.

The differences are subtle. Overall size is a difficult gauge as the large female sharp-shins, at 13 inches long, may be nearly as large as small male Cooper’s hawks, which can be only 14 inches long. The most reliable way to tell them apart is to look at the shape of the tail. In the sharp-shinned it is squared off, often notched, with a narrow white terminal band. In the Cooper’s hawk the tail is rounded with a broad white terminal band. These characters can be seen whether birds are perched or in flight.

Another field mark that is more difficult to see is the back of the head or nape. In the sharp-shinned hawk both the nape and crown (top of the head) are the same shade of gray. In the Cooper’s the nape is a lighter shade of gray and the feathers may look rough, as if the bird has the beginnings of a crest.

The juveniles have brown heads and backs, but the tail differences between the species remain. In addition, the juvenile Cooper’s hawks have less heavily marked bellies than the sharp-shinned juveniles, and the overall effect of the markings in the juveniles of both species is of vertical stripes rather than horizontal barring. There are other fine points to separating these species, which are best detailed by William S. Clark in his “Peterson Field Guide to Hawks” (1987).

It is these two species that are most likely to haunt your feeder in the winter, picking off birds with somewhat frightening efficiency. When we lived on Martha’s Vineyard, we had a clump of arborvitae near the feeder that sheltered the birds as they sortied back and forth to the feeder. One day I noticed that the feeder was entirely deserted in spite of the fine weather. I was mystified until I spotted the Cooper’s hawk perched in the upper branches of one of the arborvitaes. The neighborhood birds apparently had experience with this raptor and steered clear until it gave up and left. By contrast, my mother had a Cooper’s hawk watching over her feeder up in Merrimack County and the birds seemed oblivious. 

While it is disquieting to watch accipiters eat into your population of feeder birds, you should enjoy the opportunity to watch these hawks at your leisure. During the breeding season they retreat to the woods and are rarely seen. Buteos, particularly red-tailed hawks, are seen all the time because they are more fond of open spaces. That said, broad-winged and red-shouldered hawks do tend to be seen in the woods, but they are simply larger than the two smaller accipiter species and therefore more likely to be spotted. (The sharp-shinned has the distinction of being the smallest hawk in North America. This does not count the smaller kestrel, which is a falcon, not a hawk.) All the buteos do have the tendency to soar above the treetops or over open country, while the accipiters hunt below the canopy, although all three species are known to soar for a period on a daily basis, usually in the morning.

The goshawk is a much bigger animal and far less likely to be seen hunting birds at your feeder. Here in New Hampshire they are present all year, but it is near the southern limit of their breeding range. I got the best look at a goshawk I have ever had on Forbes Mountain up in Alexandria. He (or she) erupted out of the woods into a clearing that was dotted with junipers, saw me standing there, and veered off at a sharp angle to return to the woods. Seeing such a large bird (the females can be two feet long) move so quickly and agilely is unnerving.

The goshawk is a study in gray. The chest and belly are a light bluish-slate with fine black barring. The back and tail are darker grays and the crown is nearly black. There is a broad white line over the eye (superciliary) that extends toward the nape. The long tail has only faint or no banding in the adult, but the juveniles look much like a very large Cooper’s juvenile with a white superciliary line. In flight its wings are relatively longer than those of the other accipiters and are less rounded and more tapered.

While the Cooper’s and sharp-shinned hawks prey primarily on birds, the goshawk will also eat mammals, both large and small. Like the other accipiters, the goshawk hunts from a perch or while cruising through the forest on the wing. Clark notes that they will even pursue prey on the ground.

Clark is fond of etymology and includes a section on the derivation of each species vernacular and scientific names in his species descriptions. The goshawk is also found in Europe and its name is a combination of the Anglo-Saxon “gos” meaning goose and “havoc” meaning hawk, that is, the hawk that eats geese. The eponymous Cooper was William Cooper (1798-1864), a naturalist from New York state. French biologist Lucien Bonaparte (a nephew of the emperor) named the hawk after him. The sharp-shinned hawk is named for a raised ridge on the inside front of its tarsus (strictly speaking, the ankle, not the shin).

“Accipiter” is Latin for bird of prey and is derived from the verb “accipere,” which means to grasp, a reference to the talons. The name was given to these hawks in 1760 by French zoologist Mathurin Brisson. The trivial name “striatus” of the sharp-shinned hawk refers to the streaking of the chest and belly of the juvenile, which was described before an adult specimen. The “cooperii” construction is a descriptive genitive declension that means “of Cooper.” The northern goshawk (there are dozens of other goshawk species worldwide) is Accipiter gentilis, which is Latin for “noble,” and refers to a historical period of falconry when only nobility were permitted to fly this species.

This column was inspired by a photo a friend of mine posted to Facebook this past week, which was of a juvenile Cooper’s hawk feasting on one of her chickens. The accipiters are the original “chicken hawks,” and for that offense they were frequently shot until protections were put in place (after which it has been a merely less frequent practice). My friend was philosophical about the event and was content to watch the hawk make several meals out of the carcass. Of course, she used to work for the Ecological Society of America, so this is understandable.