Hawk Mountain's lofty mission


Conservation: Rocky east-central Pennsylvania offers a haven for birds of prey, giving scientists a good site for studying the environment.

November 19, 2001|By Michael K. Burns | Michael K. Burns,SUN STAFF

HAWK MOUNTAIN, Pa. -- Bright autumn leaves drift down to the valley floor as spread-winged hawks easily glide across the crinkled Kittatinny Ridge of the Appalachians.

There is serious purpose in the deceptively effortless flight of these magnificent birds, driven by primordial instinct and fortunate topography to follow this route in migrating to warmer wintering grounds.

Here in these rocky outcroppings of east-central Pennsylvania, their southern journey attracts another flock of pilgrims: excited bird-watchers.

Until 1934, humans climbed this rugged peak with shotguns each fall to slaughter the raptors for sport and a government bounty on "chicken hawks" and predators of favored game birds.

New York socialite Rosalie Edge was so enraged at photos of the gleeful massacres that she first leased the hillside, then bought it, to keep out the hunters. The favored redoubt of hawk killers became a hawk sanctuary, the first in the world for birds of prey.

Since then, the migration counts at Hawk Mountain have become a benchmark of environmental monitoring, the world's longest record of raptor migration. Rachel Carson used data gathered here to document the harmful effects of DDT on birds chronicled in Silent Spring.

Maurice Broun, the sanctuary's first curator, started the daily migration tally and developed landmark studies on American hawks, in addition to his main job of protecting the property from hunters.

His on-the-wing, field identification observations were eagerly adapted by Roger Tory Peterson, the pioneering bird-watching guidebook artist and writer. Most earlier naturalist studies of birds relied heavily on collected specimens -- dead creatures often killed specifically for detailed museum examination and description.

Recent fall migrations of hawks, eagles, falcons and osprey indicate a thriving population of raptors overall, which Hawk Mountain experts largely attribute to a cleaner environment. But there's always concern about shrinking habitat, especially for the forest hunters.

Official counts, radioed in hourly by official watchers at North Lookout during busy days, may vary from 15,000 to 40,000 birds in a given year, but long-term trends are the thing that ecologists pay attention to.

"We're doing well, the population of most species we see since the pesticide-era of the '60s and '70s is steady," says Keith L. Bildstein, research director for the sanctuary.

The panoramic promontories of Hawk Mountain Sanctuary are among the world's best places to view fall migrating raptors, luring more than 70,000 visitors a year. That's because the birds of prey often hug the contours of the ridge, right at eye level, for breathtaking close-ups.

Hawks are dedicated to saving energy by surfing the uplifting winds and thermals to carry them southward with minimum wing flapping.

Prevailing northwesterly winds hit Kittatinny Ridge and deflect upward in drafts for excellent gliding and soaring. Spiraling hot-air thermals rise from the valley farmlands, channeled by the forested slopes, lifting the birds as high as a mile above ground.

The Kittatinny is the southeasternmost major ridge of the Appalachians ridge-and-valley system before the birds reach the Atlantic shoreline on their southbound flight path. The north-south ridgeline is a good place for the raptors to concentrate, with abundant feeding grounds for prey.

Important for bird-watchers is that hawks and their kin migrate during the day instead of night. They are kings of these skies, the hunters and not the hunted -- especially since their protection under federal migratory bird laws in 1972.

Chunky broad-winged and red-tailed hawks and the smaller, slimmer sharp-shinned hawk are the most commonly counted species along the 2,400-acre sanctuary. Bald and golden eagles, kestrels, peregrine falcons, northern harriers and osprey also make a respectable appearance each year.

And on any day, unflappable red-headed turkey vultures can be seen floating over the valley looking for a meal that is dead on arrival. Different raptor species will travel to different winter destinations. Red-tails passing through here may "checkerboard," flying only as far as Virginia, where those resident red-tails will move a little farther south. Broad-wings and peregrines may be bound for Peru or Argentina.

In spring, the counts are much smaller. Prevailing winds blowing out of the east push the main raptor migration route farther west, away from Hawk Mountain. The slimmer sightings are also influenced by the birds' biological urgency to get back to claim favorite breeding grounds and by the scarcity of ground prey culled by winter's cold, making leisurely, concentrated travel undesirable.

From mid-August into December, the sanctuary is at its busiest. Some 200 volunteers and 17 staff members are pressed to keep track of the birds and human visitors.

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