Winter Hawks

It’s October and folks are perched on mountaintops throughout Pennsylvania watching the raptors parade south. Even on our mountain, I can sit for hours on a breezy October day and count dozens of raptors flying past.

Officially, fall raptor-watching begins in mid- August and doesn’t end until mid-December, but the largest numbers and diversity of species usually occur in October on our westernmost ridge in Pennsylvania’s Ridge-and-Valley Province.

Sharp-shinned and red-tailed hawks are the most common and numerous raptors here and on other hawk watches as well in October, but there are also plenty of Cooper’s hawks, American kestrels, ospreys, northern harriers and even a few bald and golden eagles then.

But here and there among the red-tailed hawks, I occasionally see its smaller congener Buteo lineatus, more commonly known as the red-shouldered hawk, soaring or flapping on its own as it too heads south, mostly to the southeastern United States, to spend its winter.

Even at Hawk Mountain Sanctuary, where folks are counting raptors throughout the season, they average twice as many red-tails (603) as red-shoulders (306) most years, and peak migration for red-shoulders are the last two weeks in October at many hawk watches statewide.

This is a beautiful hawk as I learned on March 8, 2015. On our way to see short-eared owls near Gettysburg, we stopped at Lake Kay in Fairfield to look at waterfowl. Perched on a nearby powerline along a back road was a red-shouldered hawk. It was absolutely still as it peered down on the roadside in search of prey.

It paid us no attention as we quietly exited the car for a closer look, first through our scope and then, as we crept nearer, our binoculars, and finally our naked eyes. I was thrilled to see close-up a bird I mostly have seen flying past or once, in late April, circling low over First Field and flaring its handsome, black-and-white striped tail. But on that March day, I had an eye-popping view of its rufous upper wing “shoulders,” hence its common name, and rufous breast and belly, the latter with light barring.

I wondered if the adult bird had spent the winter there in Adams County or if it had returned, as many do, in early March. However, it was nicknamed the “winter hawk” years ago because it often winters as far north as New England, and here in Pennsylvania it has been an occasional winter resident, preferring open lowland areas in the southeast and northwest areas of the state.

According to recent Winter Raptor Surveys, red-shoulder numbers have been increasing, reaching a high of 101 in 2014, since the 2001 beginning of this annual survey. Furthermore, most wintering red-shoulders appear to be in the south-central and northwest counties. In a paper Greg Grove and Nick Bolgiano wrote for Pennsylvania Birds back in 2013, they point out that both Christmas Bird Count and Winter Raptor Survey data “suggest that the number of wintering Red-shouldered Hawks has increased in Pennsylvania during the past decade.”

The Second Atlas of Breeding Birds in Pennsylvania shows that red-shoulders also nest in many of those wintering counties, and Grove and Bolgiano suggest that some of those birds stay on their territories year round. Adams County is on the top ten wintering counties list, so the red-shoulder we saw may have been a year-round resident.

Although red-shoulders prefer lowland mature mixed deciduous forests interspersed with marshes and swamps as well as forested valleys in the mountains for breeding, they occasionally adapt to old suburban areas with large trees and water.

Red-shoulders appear to use the same nesting territory every year and even to reuse their old nest or build a new one in the same area. Returning to Pennsylvania by early to mid-March, these monogamous raptors are already paired. However, they engage in courtship displays, both the so-called “circling flight” and “sky-dancing” between 11:00 a.m. and 1:00 p.m. for about 18 days. Usually after “sky-dancing” they mate.

During courtship, they also establish and defend their 225 to 500-acre territory and work on their nests. Those nests are primarily in deciduous trees that are larger than others in the same area and are more than halfway up in the crotch of the main tree trunk. Usually, their nests are near water and are built by both parents. They use bark strips, dead and live twigs, dried leaves, lichens and live evergreen sprigs. If they are constructing a new nest, it can take four to five weeks but they can refurbish an old nest in a week.

An average of two to four dull white eggs with an “endless variety of types and colors of marking,” are laid, ornithologist Arthur Cleveland Bent once wrote. In Pennsylvania this happens in April or May. Both sexes incubate them, beginning before the clutch is complete. Because the female has a large incubation patch and the male little or none, she incubates most of the time, and the male brings in food for her.

It takes 28 days for the eggs to hatch and the nestlings emerge covered in light brown down with wide open eyes. They grow rapidly and by two weeks of age, they stand up, lie down, and flap their wings. At six to eight weeks they can climb on branches nearby and fledge which occurs in Pennsylvania in June and July. Still, the parents continue to feed their offspring for another six to eight weeks before they are on their own.

The primary foods for both adults and young red-shoulders in the northeast United States are eastern chipmunks, mice, voles, and shrews. Other mammals include rabbits, muskrats, opossums and skunks. But they also prey on frogs, fish, toads, snakes and crayfish, hence their preference for riparian areas.

Back in 1890 in Pennsylvania, ornithologist B.H. Warren examined the stomach remains of 57 dead red-shoulders and discovered that 43 contained meadow voles, a few other small mammals, grasshoppers and other insects (mostly beetles). Nine others had frogs and insects, two had snakes and frogs, and two others small birds, small mammals, and a few beetles. None had poultry even though they were also called “hen hawks.”

They have their own predators. Great horned owls and red-tailed hawks may take over both red-shoulders’ occupied or empty nests. They also, along with raccoons, peregrine falcons, and fishers, may kill nesting adult red-shoulders, their eggs or young.

Even though their nests are well-hidden from our eyes, as we discovered one April when we were at Yellow Creek State Park in search of waterfowl, we entered a section of woods near the water to be met by the loud “kee-aah” cries of a red-shoulder that went on and on. We never did see it despite straining our eyes and tramping through the entire area.

Red-shoulder populations seem stable now, according to a 2008 continent-wide study during autumn migration counts, although they have not attained, here in Pennsylvania, their pre-DDT numbers, probably due to the loss of riparian habitat and large blocks of contiguous mature forests. Furthermore, the breaking up of these forests into small blocks favors their primary predators, the larger and more aggressive great horned owls and red-tailed hawks. Still, between the first and second atlas of breeding birds in Pennsylvania, red-shoulder numbers increased by 55 % and Breeding Bird Surveys in the commonwealth estimated a 3.6% increase per year.

Nevertheless, red-shoulders remain a species of Maintenance Concern in Pennsylvania’s Wildlife Action Plan because of their reliance on habitat that continues to disappear particularly in northwestern and north-central Pennsylvania, areas that have remained breeding hot spots for these still understudied magnificent raptors.