Sighting of red-shouldered hawk brightens spring day

Posted May 15, 2009, at 10:27 p.m.

I had just returned from my trip to New Jersey and was on my way home from the airport. It was a beautiful, clear day, if a bit chilly; with disappointment I realized spring had not quite fully sprung here yet.

Normally, the area of “The Garden State” I visit can’t hold a candle to Maine in terms of natural beauty. However, temperatures had climbed into the 60s and 70s there and spring was making a glorious return — flowering trees were in full bloom and bulbs were fairly exploding from the ground amidst luxuriant green grass.

So it was a bit disheartening to come back to the comparatively still-barren and brown landscape of Maine. Until, that is, I caught sight of the red-shouldered hawk in the sky over Route 22 in Portland.

The bird was riding thermals — warm columns of air that rise from the ground. These invisible elevators give soaring birds a lift, enabling them to conserve their energy by avoiding powered (flapping) flight as much as possible.

As thermals rise, they begin to dissipate. At the top of the thermal — often thousands of feet in the air — the bird can set its wings and glide for quite a distance before it loses altitude and needs to flap to remain aloft. At that point, if the bird is lucky, it finds another thermal and repeats the process.

Thermal utilization is a boon to migrating raptors and other soaring birds, apparently providing more than just lift. In his studies of migratory strategies, Paul Kerlinger found that gliding airspeed between thermals was faster (approx. 22 meters per second) than that provided by ridge updrafts, as referenced by “The Birds of North America,” species account.

Ridge flying does provide great benefit, though. It still enables the bird to maintain altitude and use less flapping flight than it would without the assistance of such turbulence. In his book, “How Birds Migrate,” Kerlinger writes, “Given a steady wind and a long ridge, a bird can cover more than 300 miles in one day.”

That’s why so many hawk-watching sites are located atop popular mountain lookouts. Here in Maine such locations include Cadillac Mountain in Acadia National Park and Bradbury Mountain State Park in Pownal. Spring migration counts were being conducted atop Bradbury Mountain and concluded Friday. A preliminary count of 3,845 hawks had been recorded passing the lookout, with 91 red-shouldered hawks tallied (for more information, visit www.freeportwildbirdsupply.com/hawkwatch.asp).

I only caught a quick glimpse of the hawk above Route 22, but it was enough to identify it by the crescent-shaped, translucent patches near the tips of each wing — a hallmark for red-shouldered hawks. I’d gleaned this handy identification tip from “Hawks in Flight,” by Pete Dunne, Clay Sutton and David Sibley.

This entertaining book provides detailed clues and an almost intuitive guide to identifying any high-flying hawk which would otherwise seem to be beyond the visual acuity of mere humans. Translucent feather patterns on the wings and tail, thickness of the tail bands, bold markings on the underside of the body and the overall impression of the bird’s shape and method of flight are all used to determine the bird’s identity.

Red-shouldered hawks are partial migrants; only the most northerly populations move south for the winter. In the northeastern U.S., this means birds breeding in the northern tier of states — Maine, most of Vermont and New Hampshire, upstate New York, northwestern Pennsylvania — move a short distance to mid-Atlantic and southeastern states. A small portion of the birds may over-winter in Central America, but most remain in the U.S.

These hawks tend to be early spring migrants, with migration peaking “late February through early April,” according to the BNA. When the Bradbury Mountain Hawkwatch began March 15, 66 of the birds were counted in the remaining two weeks of that month alone.

Once they arrive on their breeding grounds, red-shouldered hawks engage in lengthy courtship rituals, providing birdwatchers great opportunities to observe them. Circling in the air, the birds swing toward and away from each other, and the male performs a “sky dance” — soaring high while calling repeatedly, then diving steeply into a spiraling flight before ascending rapidly again.

The male’s calls are long, drawn-out “kee-ahhs” that can be heard from quite a distance, as I discovered one spring many years ago. Although I was not actually able to see the birds, the calls alerted me to their presence and activity. I hope to get the chance to view their territorial and courtship “dancing” this spring, if I’m lucky enough to discover where a pair is nesting.

bdnsports@bangordailynews.net

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