A week of light snow, followed by sleet and freezing rain last January, turned our mountain into an ice rink and penned me inside until it warmed above freezing. That occurred on January 25 when it was 36 degrees and dripping rain at dawn.
Late that afternoon our son, Mark, who was living in our guesthouse, called to tell me there was a northern shrike perched on the electric wire beyond our barn. I pulled on my boots and jacket and walked slowly downhill to where Mark was standing between the barn and the shed. There I had an excellent view of the shrike, which kept turning its head to look at us and twitching its tail. Mark then circled around the barn to Butterfly Loop, hoping to take a closer photograph of the bird.
But the shrike flew down past me and into the top of a small tree near the guesthouse. Next it flew into the tallest front yard black locust tree. Finally, the shrike flew away. I was thrilled because that was the first time I had ever seen one.
There was no trace of brown on the bird, which meant that it was an adult northern shrike. It looked like a brighter-colored version of a northern mockingbird with a gray head and back, black wings and a tail marked with white, a white throat, breast and belly, but it also had a distinctive black mask.
Early the following morning Mark searched for the shrike and found no trace of it. However, later in the morning, as I descended the Amphitheater Trail in First Field, I spotted the shrike at the top of a black walnut tree near the shed. But it flew off. Then, as I approached the house, it suddenly flew over the roof and away. A few minutes later Mark located it across First Field at the top of a catalpa tree.
The shrike had been using the wire and tree perches to hunt for prey. Called a “butcher bird” because it not only has a hook-tipped bill with which it kills prey with a bite to its neck but often it impales it on thorns or barbed wire or shoves it into forked branches for later consumption. Ten-inch northern shrikes will kill birds larger than themselves, for instance, 12-inch mourning doves and 11-inch blue jays. In the winter they are also looking for meadow voles and white-footed mice to consume.
Although we kept looking, we saw no further sign of the shrike until February 9. It was 31 degrees at dawn and the ground was covered with a light snow that had fallen overnight. I headed out at 9 am, bound for Greenbrier Trail. As I ambled along Butterfly Loop toward Margaret’s Woods, I paused to admire the snow-covered landscape. A bird, its tail twitching, was perched on top of the same catalpa tree across First Field where Mark had last seen the shrike. At first I thought it was a crow but through my binoculars I could see that the northern shrike was making a return visit after its first visit two weeks before. As I neared the tree it flew away.
I resumed my walk but coming back across First Field two hours later, a spot of white in a black locust tree at the base of Sapsucker Ridge turned out to be the shrike. From there it flew to the top of a pear tree and then into a black walnut sapling at the edge of First Field close to where I was standing. Lastly, it flew behind the barn and back across the field to the catalpa tree.
I had been trying to contact Mark since my early morning sighting, but he had been off birding at the Far Field. Finally, both he and his brother Dave joined me, and we all had a look at it back in the small locust tree at the base of Sapsucker Ridge. And that was our last glimpse of the elusive boreal songbird. It had enlivened what had been a dull winter for birds since neither northern finches nor red-breasted nuthatches had irrupted from the north.
Northern shrikes are also an irruptive songbird that breeds in the shrubby north from Labrador and Quebec to western Alaska. Many of them migrate south to southern Canada and the northern United States during late autumn and early winter. Every three to six years their numbers peak, and northern shrikes can be found as far south in the eastern United States as Virginia.
Most years, five to ten northern shrikes are observed in Pennsylvania especially in the northwest. They prefer to hunt on open brushy fields, which describes our First Field, as well as farm fields and strip mines. They may also hang out near bird-feeding stations and catch songbirds.
Last winter only four northern shrikes were found during the statewide Christmas Bird Count (CBC) and three during the 2020 Winter Raptor Survey (WRS), which is held from mid-January until mid-February. All three of the WRS shrikes were reported from northwest counties—Warren, Clarion, and Butler. The closest reported shrike to us was one at Bald Eagle State Park during the CBC. Irruptive northern shrikes have not been well-studied but sometimes they hold large territories of several hundred acres. Otherwise, they wander widely.
The largest recorded irruption of northern shrikes throughout North America happened in 1995-96, but in Pennsylvania it was the third largest with 50 shrikes in 29 counties. The largest in our state occurred the winter of 1999-2000 when there were 137 shrikes in 47 counties.
Paul Hess wrote a comprehensive article for Pennsylvania Birds on this irruption. It began with the sighting of two northern shrikes on October 24 in Erie County, which Hess described as “the state’s most regular shrike location even in non-invasive years.” By November, after the first strong cold front, shrikes were being reported statewide. Thirty were counted on CBCs in December and early January and shrike sightings continued until early March. Berks County in eastern Pennsylvania had the highest number (12).
Because there are few accounts of shrike ecology in North America, Hess summarized three notable features of our irruption, namely that 53% of shrikes (48) were adults and 47% (40) were immatures.
Secondly, only 20% held territories, and they were mostly adults, while the rest wandered, responding to food and weather conditions.
Thirdly, the prey they caught were primarily songbirds at bird feeders because meadow voles were scarce that year throughout the state.
Since that irruption, Pennsylvania has had two more, according to Greg Grove, who started the Winter Raptor Survey in 2000. Our second largest shrike irruption was 2007-08 with 80 shrikes in 39 counties. That was followed by a smaller irruption in 2011-12 with 44 shrikes in 27 counties.
Northern shrikes start returning north from Pennsylvania by the fourth week in February or first week in March. While they may pair up on winter territories, even far south, most courtship chasing, feeding, and aggressive displays by males toward females occurs on their breeding grounds.
Both sexes also sing either two-phrase, thrasher-like imitative songs of nearby bird species or sweet warbles and harsh screeches.
The male feeds the female during late courtship, nest-building, laying, incubation and the early nestling period. The female chooses the nesting site in late April or early May in shrubby willow trees or spruce conifers. She places it in a fork of a branch near the trunk usually eight feet from the ground. She also brings most of the nesting materials aided by the male. The nest is a large, deep, bulky cup filled with ptarmigan feathers, animal hair, and dried moss and lined with grasses and sedges.
In the nest she lays 4 to 9 grayish or greenish white eggs spotted heavily with brown and incubates them 14 to 21 days while the male is busy feeding her and defending a 360-acre hunting territory as well as a 7-acre nesting territory. Mostly the male hunts for grasshoppers, beetles, bumblebees, insect larvae and spiders during the summer months.
The offspring spend 18 to 20 days as nestlings and another several weeks as fledglings being fed by their parents and taught how to hunt. By mid-summer the fledglings are on their own, and sometimes the siblings stay together and join other broods of immatures as they continue to hone their hunting skills.
By mid-September these groups disperse and individually move along river corridors out of the boreal forest into open country. They also follow ridge lines like small hawks do, flying just above the tree tops as they head south for the winter.
Because seeing a northern shrike here in winter is a rare privilege, I don’t expect to see one hovering over our First Field this winter. But Pennsylvania is overdue for another northern shrike irruption
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