Counting Raptors in Mid-Winter

Last winter was the 20th year of the Winter Raptor Survey. This innovative survey is the brainchild of Greg Grove, who is a retired biochemist from Penn State University, the compiler of the Stone Mountain Hawk Watch and the editor of Pennsylvania Birds magazine.

The Winter Raptor Survey (WRS) is designed to count all raptors and vultures along pre-determined back road routes through open habitat in Pennsylvania. These routes vary in length from between 25 and 90 miles and remain the same from year to year.

We signed on the first year to run a route in Sinking Valley, a mostly open farm valley between Tyrone and Altoona in Blair County, a valley that I gaze down at every time I take a walk on our Laurel Ridge Trail. This valley has both Amish and modern farm operations and is almost entirely enclosed by forested Bald Eagle (locally known as Brush) Mountain. Much of the mountain not owned by private persons is part of SGL#166.

My husband, Bruce, designed our 34-mile route around this small valley, and I have been the principal observer most years, although occasionally we’ve been joined by one or the other of our two birder sons, Steve and Mark. Last winter Mark joined us, sitting in the front passenger seat, while I occupied the back seat and Bruce, as usual, was the driver.

Unlike the Christmas Bird Count, where counters have one pre-designated day to count birds, WRS participants can choose any date set by Grove over a several week period. Last winter it was January 12 to February 17. We chose a 32-degree, overcast morning with a light breeze in late January.

Shortly after beginning at 8:51 am, we spotted a mature red-tailed hawk sitting high in a tree on a road where we had never before seen a raptor during our previous surveys. This sighting seemed to be a good omen for our WRS.

But we drove for several miles, seeing no raptors until we neared a farm field at the entrance to Fort Roberdeau County Park. There we stopped to watch a turkey vulture and two black vultures picking over the carcass of a small deer. They were the first vultures we had ever gotten on a WRS.

As it turned out, according to Grove’s article in Pennsylvania Birds (Dec. 2019-February 2020) entitled “The 2020 Winter Raptor Survey in Pennsylvania,” the mild winter weather caused record numbers of both vulture species to stay north, especially in southeastern Pennsylvania with Lancaster and Chester counties accounting for 43% of all recorded vultures in the state. In addition, Greg wrote, “Turkey and Black Vultures were found in 39 and 29 counties, respectively, both the highest ever for the Pennsylvania WRS.”

We couldn’t count or even identify the vultures high in the sky heading for the farm field because a sudden snow squall hit, and Bruce could barely see the road. Luckily, we soon drove out of the snow and on to a series of back roads, mostly in the Amish section of the valley, where we spotted a pair of adult bald eagles on one distant field that flew off and over an incline. Probably they were the pair that had set up housekeeping on the other side of our mountain on the game lands.

Grove later reported that while the 20th WRS bald eagle count of 509 was less than the record-setting 600 of the 2018 WRS, it too could be accounted for by the mild winter. During colder winters, bald eagles congregate on one route in Bucks County along the Delaware River and another in Lancaster County along the Susquehanna River where there is plentiful food, but in 2020 the birds weren’t as dependent on those two major rivers. Still, despite being recorded in 56 counties, Lancaster with 81 and Bucks with 42 still had the highest numbers.

On an electric line along another back road directly below an Amish farm owned by a family that erects a couple purple martin houses every spring, perched our only American kestrel, a lovely male. Again, the mild weather led to a higher than usual kestrel count for Pennsylvania (623), the fourth highest ever; the highest (711) occurred in 2017. Franklin County was way out in front with 50 kestrels. Most years we manage to find a single kestrel somewhere in the valley, although on a longer route in the southern part of our county, seven kestrels were recorded in 2020.

In an email to me, Grove wrote that the 20 years of WRS data “shows evidence of kestrel decline especially in eastern Pennsylvania.” Furthermore, “the WRS has shown the importance of the ridge and valley farmlands, where most of the kestrels winter.”

The rest of our route was less exciting, but we managed to find four more mature red-tailed hawks sitting on trees in different parts of the valley. Statewide, red-tailed hawks numbered 3242 with Huntingdon County’s tally, at 150, the highest.

Even though we had our best WRS ever, with five species, we had missed northern harriers, another open country raptor. According to Grove’s article in Pennsylvania Birds, northern harrier numbers are dependent on several factors such as their small mammal prey base in open fields and the newly-reported study by hawk watch researchers that has uncovered the harriers’ four-year population cycle. But most important of all was probably the mild weather and lack of snow cover that led to a 104 count in 2020 compared to the lowest ever of 59 during the cold and snowy 2019 winter. Grasslands on reclaimed strip mines are particularly favored by northern harriers and thus the Clarion County grasslands, free of snow-cover in 2020, led the state with 12.

Rough-legged hawks, a northern species that breeds in North America from Alaska to Labrador, winter across Canada and throughout much of the United States including Pennsylvania. They too prefer large open fields with small mammal prey. But only 30 were recorded, the lowest number per hours surveyed during the 20 years of the WRS. Most of them were scattered across the northern half of the state, but the highest number occurred in eastern Centre County with five in Penn’s Valley.

Red-shouldered hawks, in contrast, continue to increase their numbers every year, setting another record in 2020 of 188. Most of them were concentrated in southeast and south-central counties with 31 in Adams County, although Butler (18), Crawford (14) and Mercer (13), all in the northwest, had the next highest counts. These forest-loving hawks have traditionally bred and wintered in lowland deciduous or mixed forests interspersed with wetlands and also in the forested mountain valleys, according to McWilliams and Brauning in The Birds of Pennsylvania.

But Grove in his email wrote that, “The most dramatic increases are in the southeast, and others have been speculating that Red-shoulders may be becoming somewhat ‘suburbanized.’ We can also see support for the idea that Pennsylvania’s breeding Red-shoulders apparently stay on territory through winter—evident in the large number of WRS RSs [Red-shoulders] in NW PA, even though weather there is [the] most severe in the state.”

Other forest raptors had lower numbers than red-shoulders—113 Cooper’s hawks, 39 sharp-shinned hawks, five golden eagles and only a single northern goshawk in Franklin County. The much higher count of Cooper’s hawks reflect growing numbers in the state, in contrast to the dwindling numbers of sharp-shins. Both prey on songbirds at feeders during the winter and provide excellent views to those of us who are feeder watchers. Like sharp-shins, northern goshawk numbers have been falling in Pennsylvania and are now listed as Vulnerable in the state’s Wildlife Action Plan. Most eastern golden eagles, which nest in northern Quebec Province, head further south than Pennsylvania in the winter.

And finally the 16 merlins and 12 peregrine falcons statewide inhabit open country near water and near or in urban areas. Merlins only recently began breeding in northern Pennsylvania, their southernmost breeding area in the eastern United States. During the second breeding bird atlasing period six nests were confirmed in Bradford, Sullivan, Pike and Warren counties. However, during the WRS merlins were found in the central and southern counties. There were four peregrine falcons in the northwest and the rest in central and southern Pennsylvania.

Pennsylvania hawk watchers continue to have enthusiasm for the WRS and now run over 200 routes in 66 of our 67 counties. Grove thinks that’s because we are a top hawk-watching state and birders are looking for an excuse to get out in mid-winter and count birds.

When Grove first launched the WRS, he had already been looking for wintering hawks on his own, but “I thought it would be worthwhile to do so using consistent, repeated routes in order to get data that would have some degree of scientific value. To look for trends over years and make distribution maps.”

And that’s exactly what has happened. Congratulations to Grove for brightening our winter days!