A small group of people clustered together on the rocky ledges of Cadillac Mountain in Acadia National Park. Some stood, some sat; some had binoculars or spotting scopes. All of us waited patiently for the passage of migrating hawks along the mountain’s ridge.

It was a slow day, so we waited quite awhile. At length, a bird did show up, but it was not a raptor, it was just a robin. A few herring and ring-billed gulls cruised the parking lot over by the gift store, no doubt on the lookout for careless garbage disposal.

A small passenger plane flew over Frenchman Bay.

“That,” said park ranger Bryant Woods, “is what is known in birding circles as a ‘gas hawk.'”

We all laughed.

Then, without notice, a real hawk came whizzing over the ridge, almost at eye level. At first it headed straight toward us, then angled westward, giving us spectacular close-up views. It was a sharp-shinned hawk.

These small, woodland hawks are the most abundant birds of prey sighted from atop Cadillac during migration. The highest yearly count of these hawks occurred in 2001, when 1,476 were seen that autumn. A high of 188 were seen in a single day in 1998, which must have given hawk-watchers ample opportunities to practice identifying it.

The “sharpie” is typically smaller than a crow, and thus smaller than its look-alike cousin, the Cooper’s hawk. However, this is no hard and fast rule because of size differences between the sexes of both birds. Females are always larger than males; particularly large female sharp-shins may be confused with small male Cooper’s hawks.

There are more reliable field marks to use to identify this bird. One is the tail: it is more squared-off and straight edged, while a Cooper’s hawk tail is rounded. Both of these hawks have long slender tails and broad, rounded wings, but the sharp-shinned hawk appears to have a smaller head in relation to its body size.

In powered flight, sharpies tend to flap more than they glide, and their flaps are quick and snappy. It takes some time to distinguish these subtle differences; birders have been known to have fits over distinguishing between the two. However, don’t let this discourage you; the beauty of the birds is still there for anyone to enjoy, and the phenomenon of migration is an awesome spectacle.

Acadia has been conducting hawk watches from Cadillac now for eight years. Park rangers are present to tally raptors, educate people about what to look for in identifying them, and relate interesting life histories of the birds. Rangers are present from 9 a.m. to 2 p.m. every day; for more information, please call Bryant Woods at 288-3338.

Cadillac Mountain is just one of the sites that hosts official hawk watches in the United States. Places such as Cape May, New Jersey, and Hawk Mountain, Pa., are just two other locations that consistently see large numbers of migrating raptors, especially in the fall. An additional opportunity to learn how to identify migrating hawks will take place on Sept. 21, at Beech Mountain in Acadia National Park.

Maine Audubon member Jerry Smith will host this event, and will also be conducting a slide show on raptor identification on Sept. 19, in Ellsworth. For more information, please call the Fields Pond Nature Center at 989-2591.

On a similar note, Bob Duchesne and I will be talking about bird feeding and gardening for wildlife at Windswept Gardens in Bangor today. Please call 989-2591 for more information.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com