Every winter we have at least one unusual bird visitor. The winter before last it was the northern shrike. Last winter, during the pandemic, most birders were excited about the superflight south of boreal birds and welcomed huge numbers of pine siskins, red-breasted nuthatches and common redpolls, as well as evening grosbeaks and even hoary redpolls at their feeders. We saw only an occasional pine siskin with a flock of American goldfinches.

Instead, we were surprised by the appearance of a northern mockingbird on November 10 during a long period of Indian summer weather.

While northern mockingbirds are common yard birds in much of Pennsylvania, we had, up until 2020, only five detections of these birds on our mountain, and they had been in the spring. But our son, Mark, who was living in our guesthouse with his wife Paola and his brother, Dave, at the time, described the November mocker as a skulker that would appear around six in the morning and move quickly from its shelter in the huge old barberry hedge that stretches several hundred feet from the guesthouse to the shed, up to a lilac shrub near our veranda and then on to large forsythia bushes near our garage.

Mark continued to see the mocker every morning, but I didn’t have my first sighting until a cold day late in November as I headed across First Field. In the middle of the field, perched in a large, native, black haw shrub with four American tree sparrows, was the northern mockingbird. I had a good, long look at her mostly gray body with whitish breast and belly, white wing bars, and, when she finally flew, a flash of black and white tail feathers.

I decided she was a female because she never sang but merely “chipped” a few times at dawn. Female mockingbirds sing quietly only during nesting time, but males sing most of the year. Furthermore, according to K.C. Derrickson, who studied mockingbirds in southeastern Pennsylvania and Maryland, many females in Pennsylvania establish their own winter territories in November apart from their mates, based on the available fruit, cultivated or wild, in an area, especially multiflora rosehips. Although we had a few of the latter around the perimeter of First Field, we had a lot more barberry, mile-a-minute and even an old apple tree with apples still clinging to it.

My husband, Bruce, had the next sighting on a bitter cold afternoon in early December when she landed briefly on a hackberry tree outside the sunroom. Three days later, on December 10, I saw her again, this time alone, in the black haw shrub. She sat still as I crept closer and closer. Then she spread her black and white tail before flying across the field toward the barberry shrubs at the edge of Margaret’s Woods.

Northern mockingbirds prefer early successional habitat at low elevation (less than 1,300 feet), and Mark established that they had territories at the base of our mountain on the Sinking Valley side. This rural area with brushy pasture and agricultural fields bordered by dense shrubs along with the mowed lawns and shrubs of suburban homes is ideal mocker habitat, and we thought that “our” mocker had followed the powerline right-of-way that crosses the valley up to our property.

She made her appearance again during our Christmas Bird Count on December 20, and Dave saw her on a tree branch near his front porch on December 27.

Dave has had a Twitter account and blog for over a decade that he calls The Morning Porch, where he recorded her sitting in a bush beside our stream and chasing off other birds that tried to drink there on January 5. Mockingbirds are known to be aggressive toward their own species and other bird species too throughout the year.

The following day Bruce saw her land on our large bird feeder hanging on our back porch, but mockers are not usually feeder birds unless there is fruit or suet in feeder areas, neither of which we had.

On January 8 I had my best and, as it turned out, my last view of her. I had followed a deer trail through the dried goldenrod of First Field to the back of the barberry hedge. I pished and out from its depths popped the mockingbird. She sat on a hedge branch for a minute or so and then flew to the old apple tree below the hedge, where she poked at a few wizened apples and ate a little before flying away.

Dave had three more reports on his Morning Porch. The first was on January 12 when a mixed flock of winter birds flitted through the yard and the mockingbird flew over the guesthouse and peacefully joined them at a half-frozen seep.

On January 22 he wrote, “Half an hour before sunrise, the first inquisitive ‘chirps,’ mockingbird,” and finally on January 27, “Is it night or day? The 7 o’clock factory whistle [in our town] has the answer. Two minutes later the mockingbird begins to chirp—that take-charge tone.”

We can only hope she returned to the valley because after that came days of snow and cold that blanketed our mountain with more than a foot of snow and ice that lasted throughout February.

A member of the Mimidae family, the Latin name of the northern mockingbird is Mimus polyglottos roughly translated as “many-tongued mimic.” Mockingbirds, as a whole, don’t only mimic the sounds and calls of at least 200 songbirds but also a wide variety of natural and human-made sounds. For instance, one mockingbird at Boston’s Arnold Arboretum mimicked 39 birdsongs, 50 bird calls, and a frog and cricket, and the average number of song types of four males in southeastern Pennsylvania was 148 in 1980 and 167 in 1981.

Mockingbirds sing all day and sometimes all night especially if they are unmated males, beginning in February through most of November. Mockers also may have a different slate of songs for fall and spring and are known as open-ended learners, like parrots and European starlings, meaning that they continue to learn new songs throughout their lives. They sit and sing on top of shrubs, fences, trees, utility lines and poles and walk, hop, or run on the ground with their tails cocked up. The male’s singing is thought to be both a way to attract and stimulate his mate and to defend his territory from other male mockingbirds.

Males will fight over territory boundaries by first flying toward each other, landing near the boundary and silently hopping from one side to another. When this approach doesn’t work, they may fly at each other and grab with their wings and claws and peck. While males keep off males, females keep away other females.

Northern mockingbirds are mostly monogamous and some pairs stay together for life. In Pennsylvania Derrickson followed one pair for six years. In addition to singing, a male mockingbird attracts a female by building the outer twig foundation of several nests in shrubs and trees three to 10 feet from the ground. She then chooses one of those nests and lines the cup-shaped nest with grasses, rootlets, leaves and even such trash as dental floss, laundry lint, bandages, duct tape, pieces of plastic and aluminum foil.

In southeastern Pennsylvania, a female mockingbird begins laying her three to four pale blue or greenish-white eggs spotted with red or brown in mid-April and incubates them for 12 to 14 days. The male perches on a high point nearby and guards her, the eggs, and later the nestlings from predators such as blue jays, fish and American crows, red-tailed hawks, snakes, squirrels, raccoons, opossums, cats and even humans by chasing them away from the nest. Sometimes as many as six mockingbird neighbors will join together to mob and chase away possible nest predators.

The nestlings are born naked, blind, and covered with light down. Both parents feed them 82% arthropods and 18% fruit. The nestlings fledge fully feathered at 12 days of age and can fly well when they are 20 days old. The parents feed them for three weeks more, but the male often takes complete charge if the female starts refurbishing another nest and laying eggs for a second brood.

Immatures never breed on their natal territory and can disperse up to 200 miles which may be how what used to be mainly a bird of the southern United States in the early nineteenth century has become a bird that nests as far north as southern Canada.

In Pennsylvania mockingbirds have been moving northward since the 1950s, although avoiding densely forested areas across the northern tier. They are still most common in southeastern Pennsylvania but are also plentiful in the Ridge-and-Valley Province and in southwestern Pennsylvania including the Pittsburgh Low Plateau. Altogether, the state has an estimated 200,000 singing males so we should have no trouble hearing even more of the mockingbirds in years to come.