The Many-Tongued Mimic

close-up of a mockingbird's head with an insect in its bill
northern mockingbird portrait by Veit (CC BY-ND 2.0)

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.

mockingbird sitting on a branch with red berries
female northern mockingbird by Lucina M (CC BY-NC 2.0)

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.

hunched-up mockingbird sitting on a bare branch
mockingbird wintering in southern Vermont by Putneypics (CC BY-NC 2.0)

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.

a mockingbird eating a crabapple by Stan Lup (CC BY-NC-ND 2.0)

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.

singing mockingbird by Stan Lupo (CC BY-NC-ND 2.0)

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.

two brown-speckled blue eggs in a nest
eggs of a northern mockingbird in Texas by Rich Mooney (CC BY-NC-ND 2.0)

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.

four baby birds in a nest, two with mouths agape
mockingbird chicks in Florida by Jim Mullhaupt (CC BY-NC-ND 2.0)

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.

a mockingbird in flight
an over-wintering mockingbird in Vermont takes flight by Putneypics (CC BY-NC 2.0)

Surveying Breeding Birds

Ever since I began documenting bird species on our central Pennsylvania mountaintop back in 1971, bird numbers and species have been declining, not only here but throughout the world. Most of these estimates by scientists are based on a wide variety of bird counts and studies, especially in North America and Western Europe. But in the last couple decades, due to the ease of submitting bird lists online, birders and scientists worldwide have joined in.

The Important Bird Area sign at the entrance to the hollow, chewed by a porcupine

The Important Bird Area sign at the entrance to the hollow, chewed by a porcupine (Photo by Dave Bonta on Flickr)

Here in Pennsylvania we’ve conducted two breeding bird atlasing projects (1983-1989) and (2004-2009). In addition, Audubon Pennsylvania launched its Important Bird Areas breeding bird point count in 2003. Since our Bald Eagle Ridge property is part of IBA#32, my son Dave and I participated in the count from 2005 to 2014. Each time we followed the identical protocol, counting birds at the same 15 points 500 feet apart in some of the varied habitats on our property.

That first year we conducted two counts. The one in May yielded 48 species and the second in June 47 species. But by 2014, when the IBA point count project was discontinued, our species number was down to 37.

The steep slopes of Laurel Ridge

The steep slopes of Laurel Ridge (Photo by Dave Bonta on Flickr)

I had grown increasingly dissatisfied by this approach because I knew that we had far more species breeding on our mountain than the point count indicated. And the route that we had to follow in less than three early morning hours up and down steep slopes, was becoming more difficult as I entered my seventies.

In the meantime, the Pennsylvania Society for Ornithology started its ongoing Breeding Bird Blitz in 2015. This survey encourages teams of birders to cover the commonwealth during four days in mid-June in order to get a quick snapshot of the state’s breeding birds and put their reports on eBird, the online reporting system that birders throughout the world use.

Last June I decided to spend three days of the Breeding Bird Blitz on foot searching for breeding birds on our mountain, following no protocol but my own knowledge of an area I have been living in and studying for almost five decades.

A cerulean warbler at Raccoon Creek State Park

A cerulean warbler at Raccoon Creek State Park (Photo by Steve Valasek in Flickr, Creative Commons license)

I examined Pennsylvania Audubon’s 13 priority birds list for the state, all of which are threatened in terms of the species’ long-term survival according to rigorous analysis by qualified scientists. I hoped to find at least a few of the songbirds, specifically cerulean warblers, wood thrushes, golden-winged warblers, and black-throated blue warblers, all of which have nested here in the past. There was also a chance that I would find a breeding American woodcock or bald eagle, the latter now nesting regularly at the other end of our Brush Mountain portion of Bald Eagle Mountain.

But I was absolutely certain that I would not find breeding piping plovers, northern goshawks, bobolinks, prothonotary warblers, Canada warblers, common terns, and grasshopper sparrows because we have no habitat for those species.

On day one—June 16—I was out before 6:00 a.m. and counted an easy 11 species singing in our couple acres of overgrown yard—gray catbird, chipping sparrow, eastern towhee, indigo bunting, field sparrow, red-eyed vireo, common yellowthroat, eastern phoebe, song sparrow, eastern wood-pewee, and tufted titmouse.

I added other species as I hiked up the forested Dump, Short Circuit, and First Field trails, through our 43-year-old Norway spruce grove, over to the still-filled vernal ponds, along Sapsucker Ridge Trail to the Far Field and back on the Far Field Road, Laurel Ridge Trail and Guesthouse Trail—a two –mile circuit that brought me home by 7:22 a.m. Altogether, I garnered 27 species, several of which were repeats from my yard count but also it included six scarlet tanagers, nine ovenbirds, four hooded warblers, three black-throated green warblers, and one black-and-white warbler. All of those species were listed as migrating songbirds whose numbers have been cut in half since the 1960s, which sounded about right, because I had passed whole areas on our mountain that were silent in our closed canopy forest.

A wood thrush in Allegheny County

A wood thrush in Allegheny County (Photo by Tom Benson on Flickr, Creative Commons license)

I especially remembered back in the 1970s the wood thrushes that nested in many of our mountain laurel shrubs, some as close as 10 feet from one another. Yet today our bushes are mostly dead and dying from a leaf fungus and wood thrushes have deserted most of our forest. I still can hear their ethereal songs, but I have to hike much farther to find even one wood thrush.

The following morning I walked part way down our hollow road to record three Acadian flycatchers and two worm-eating warblers, but with all the rain we had been having, our small stream, which is usually low by mid-June, was flowing as strongly as it does in early spring and was so noisy that it was difficult to hear much except the loud birds—more scarlet tanagers, red-eyed vireos, and the Acadian flycatchers.

Finally, I hiked up a flooded Dogwood Knoll and along the soggy Ten Springs Trail to hear an eastern wood-pewee, chorusing tufted titmice, and at last, a wood thrush. Again, I covered about two miles in the early morning.

Down the hollow road next to an old black birch

Down the hollow road next to an old black birch (Photo by Dave Bonta on Flickr)

The last day, which was hot and humid, I was down our hollow road before the sun rose at 5:38, but I only added more numbers to my list even though I walked most of the mile-and-a-half road. Still, the noisy stream continued to defeat me and again I retreated upslope, this time to Greenbrier Trail where I picked up American redstarts, hooded warblers, eastern towhees, a common flicker, eastern wood-pewee, scarlet tanager, and red-bellied woodpecker, several northern cardinals, and a brown-headed cowbird.

By then my socks and boots were thoroughly soaked by the invasive, knee-high, Japanese stiltgrass that clogs the old logging roads and, incidentally, was brought in on logging trucks back in 1991, before we could purchase this part of our property. Already, it was heating up, and by the time I reached Butterfly Loop around our 37-acre First Field, it felt like a blast furnace. Still, I persisted and was rewarded by a gorgeous, singing rose-breasted grosbeak, but not a golden-winged warbler as in years past.

Back at our yard, a cerulean warbler and gray catbird joined the morning chorus. The veranda eastern phoebe was sitting on her second clutch of eggs, the yard nesting blue-gray gnatcatcher called, and a chipping sparrow buzzed louder than usual.

Then it was time to tally up my numbers and species of birds during the three-day period. Even though I had covered the IBA point count area Dave and I had followed as well as other portions of our property, I ended up with 38 species, only one more than we had gotten back in 2014.

A red-eyed vireo in Chester County

A red-eyed vireo in Chester County (Photo by Kelly Colgan Azar to Flickr, Creative Commons license)

The winner in numbers remained the same—the red-eyed vireo—with 33—followed by 17 eastern towhees, 12 hooded warblers, 10 ovenbirds, scarlet tanagers, common yellowthroats and indigo buntings, seven American redstarts and eastern wood-pewees, five wood thrushes, and three cerulean warblers and black-throated green warblers. But alas I found not even one black-throated blue warbler or golden-winged warbler and no surprise birds either. I did, however, find all five of the most common bird species in Pennsylvania, according to the Second Atlas of Breeding Birds in Pennsylvania—American robins, song sparrows, chipping sparrows, red-eyed vireos, and gray catbirds.

But since I had been listening to and counting singing species since late April, I had also recorded the songs of other breeders here, for instance, blue-headed vireos, brown thrashers, Louisiana waterthrushes, whip-poor-wills, wild turkeys, barred owls, yellow-billed cuckoos, black-capped chickadees, white-breasted-nuthatches, common ravens, American crows, house wrens, common grackles, pileated, hairy and downy woodpeckers, as well as the calls and courtship displays of red-tailed hawks, Cooper’s hawks, and turkey vultures, in all at least 57 species.

This exercise led me to conclude that both Breeding Bird Blitzes and in depth, breeding season coverage of as much habitat as possible in Pennsylvania are necessary to assess the numbers, species, and overall health of our breeding birds, a task that continues to be done by both professionals and amateurs who cherish our birds.

 

Hairy Woodpeckers

On a cold winter morning my husband Bruce and I were sitting in our kitchen and eating our usual Saturday breakfast of muffins and cheese omelets. I looked out our kitchen window and noticed two woodpeckers sparring on the trunk of the driveway black walnut tree. At first I thought they were our yard red-bellied woodpeckers, but after looking through my binoculars, I realized that one was a male red-bellied and the other a male hairy woodpecker.

A portrait of a male hairy woodpecker

A portrait of a male hairy woodpecker (Photo by Teddy Llovet on Flickr, Creative Commons license)

Finally, the hairy retreated to the open ground around the black walnut tree where he poked in it for a couple minutes before flying off. I wondered if the red-bellied might have been defending his stash of seeds and nuts shoved in the crevices of the black walnut tree trunk and if instead the hairy had acknowledged defeat by searching for pieces of black walnuts on the ground.

During the fall and winter, hairy woodpeckers eat mast– acorns, hazelnuts, and beechnuts—but I imagine black walnuts are acceptable since hairies also consume a variety of seeds and nuts at bird feeders including cracked walnuts, pecans, and sunflower seeds. Still, I was surprised to see hairy woodpeckers in our yard since they prefer a forest of large trees, although they will live where there are mature shade trees in small woodlots, wooded parks, cemeteries or residential areas.

A female hairy woodpecker with a berry in its beak

A female hairy woodpecker with a berry in her beak (Photo by Dave Chase, 2012 Photo Contest, Seney NWR, on Flickr, Creative Commons license)

They also come readily to bird feeders in such residential areas, but they don’t come to our feeders on a central Pennsylvania mountain. Our feeder woodpeckers are red-bellied and downy woodpeckers. Those same species nest in holes in our yard black walnut and black locust trees. The hairies prefer our mature forest trees for foraging because the larvae of wood-boring insects make up 21 to 41 percent of their food throughout the year, along with ants, spiders, millipedes and beetles as well as wild berries and mast.

But during last winter’s warm February and early March, hairy woodpeckers visited our yard. First the male hairy revisited the plowed area, poking his bill repeatedly in the thawing ground. Then he flew into the driveway walnut tree and climbed to the top before flying away. He returned a couple days later with a female hairy and both, along with the yard red-bellied pair, busily poked in the open yard for food through a re-frozen earth.

In late February, I heard and then found a pair of hairy woodpeckers high in a tree on Greenbrier Trail engaged in courtship behavior, extending their necks, their bills pointing upward, bobbing their heads from side to side and flicking their wings as they circled the tree trunk. I doubted this was our yard-visiting pair because studies show that in a mature upland forest such as ours, a territory is on average 6.5 acres and Greenbrier Trail is a half mile from our home.

On the other hand, during the winter, hairy woodpeckers in Michigan have territories of 800 acres, which is larger than our square mile property. Furthermore, while some studies find that a pair of hairies have separate winter territories and renew their pair bonds in early spring, other studies find that pairs remain together throughout the winter.

A woodpecker meet-up—a hairy and a northern flicker having a dispute

A woodpecker meet-up—a hairy and a northern flicker having a dispute (Photo by Dan Streiffert on Flickr, Creative Commons license)

In early March our yard-visiting pair joined a woodpecker meet-up near and on the driveway black walnut tree. Presumably, the hairies, along with a pair of downies and the red-bellied pair, were interested in the nesting cavity 30 feet high in the tree. Finally, the hairies retreated to the ground, poked their bills at the black walnut remnants and flew away.

That was the last they appeared in our yard, but I continued to see and hear the explosive “peek” calls of hairies in our forest the rest of the year. I knew from hairy nests I had watched that they favored high, dead, wild black cherry tree limbs here for nesting, and once the dead limb of a large black locust tree. I’ve also seen pairs in our mostly oak forest, and until the second half of the nestling period when the nestlings are incredibly noisy, the adult hairies are more wary than the smaller, look-alike downy woodpeckers.

Hairy woodpeckers are related to downy woodpeckers and in 2018 the American Ornithological Society changed their genus name Picoides along with six other western and southern North American woodpeckers back to Dryobates, a genus assigned to all these four-toed woodpeckers both here and in the Old World in 1826. In addition to being in the Picoides genus with three-toed woodpeckers, the four-toed woodpeckers had other anatomical as well as genetic difference with them, hence the genus change.

A downy woodpecker (left) on a feeder with a hairy woodpecker

A downy woodpecker (left) on a feeder with a hairy woodpecker (Photo by Paul Hurtado on Flickr, Creative Commons license)

Another study pointed out that hairy and downy woodpeckers look so similar that they are difficult to distinguish in the field, yet they are not closely related. Downy woodpeckers belong to a group of four small Dryobates while hairy woodpeckers are in a group of four larger Dryobates. Neither woodpecker resembles others in their group as much as they resemble each other.

Some researchers believe that downy woodpeckers evolved mimetic plumage to avoid attacks from hairy woodpeckers, the so-called “Hairy Woodpecker Trickery” hypothesis. But a recent study of hairy and downy woodpecker interactions at the feeders of Project FeederWatch observers by three Cornell Laboratory of Ornithology scientists seems to disprove that theory. They found that downy woodpeckers were often the target of hairy woodpeckers and chased the downies from feeders. However the downies were unusually dominant when competing with birds larger than them such as northern cardinals. The scientists hypothesize that downies may use their resemblance to hairies to fool other species into believing they are hairies, the so-called “Innocent Bystander Trickery” hypothesis.

Both woodpeckers have white breasts and backs, black-and-white striped heads, black wings spotted with white, and clear white outer tail feathers, but the hairy woodpecker is about nine inches to the downy’s six, has a much heavier and longer bill and usually lacks the black markings on the outer tail feathers of a downy. The males of both species have a red patch on the back of their heads and the females do not.

A male hairy woodpecker at his nest hole

A male hairy woodpecker at his nest hole (Photo by Rich Hoeg on Flickr, Creative Commons license)

Here on our mountain hairy woodpeckers begin to excavate nest holes in mid-April. The male does most of the work because his bill is 10 percent longer than the female’s. They mate during nest-building and egg-laying. Their nest cavity is dug in a dead or dying tree limb five to 40 feet from the ground, and it is 10 to 15 inches deep, with an entrance hole 1 ¾ to 2 inches in diameter. Its base contains a soft bed of wood chips on which the female lays six to eight white eggs. Both parents incubate the eggs, the male alternating with the female during the day and incubating on his own throughout the night.

After 11 to 12 days, their altricial young hatch and remain in the nest for 28 to 30 days. But the adults switch from entering the nest cavity while feeding the nestlings to feeding from the outside when the nestlings are about 16 days old. Then the nestlings climb up to the nest entrance and the parents land on the limb and poke their bills, crammed with insects, into the bills of loudly chirping youngsters. That’s when I located three nests. However, their chirping may attract predators such as black rat snakes, predators on eggs and young, as well as eastern screech-owls, European starlings, house sparrows or red-bellied woodpeckers—all predators on hairy woodpecker nestlings. The nest hole is too small to admit raccoons and gray squirrels, and adult hairies keep them away with their formidable bills.

An adult male hairy woodpecker outside a nest hole with a juvenile male inside

An adult male hairy woodpecker outside a nest hole with a juvenile male inside (Photo by Mick Thompson/Eastside Audubon on Flickr, Creative Commons license)

The parents were also noisy when I watched their nests, emitting loud, rapid-fire “queek, queek, queek” calls for 10 minutes or more whenever I entered their territory and announcing their impending arrival at the nest with far-off calls, which caused their nestlings to chirp even louder. The parents even engaged in “demonstrative drumming” on nearby trees to protest my presence.

When the nestlings are old enough to fledge, the parents use a couple methods to entice them from the nest. One is to hold food out of reach, forcing them to lean out a little too far, and the other is to starve them, making them so hungry that they tumble out. Then the parents continue to care for them as long as six more weeks which is why they have only one brood a year.

A hairy woodpecker at a feeder in Danville, PA

A hairy woodpecker at a feeder in Danville, PA (Photo by fishhawk on Flickr, Creative Commons license)

Hairy woodpeckers are common and widespread throughout their continent-wide range, and in Pennsylvania their numbers increased from the first to the second breeding bird atlasing periods. The highest densities are in the forested areas of central and northern Pennsylvania and the lowest in the Piedmont and other areas with sparse forest cover.

With an estimated 97,000 hairy woodpeckers in Pennsylvania, we should have ample chances to observe these fascinating birds in our forests, wooded yards, and at our bird feeders throughout the year.

 

Jaybirds

Every winter my feeder birds are mostly the same, both in species and numbers. But usually there is at least one surprise, even in winters when no northern finch irruptions occur.

A blue jay on a feeder in Montgomery County, PA

A blue jay on a feeder in Montgomery County, PA (Photo by Brian Henderson on Flickr, Creative Commons license)

Last winter was the year of blue jays, often nicknamed “jaybirds” because of their calls.

We live tucked away by ourselves atop a mountain so we’ve never had more than a couple blue jays at our feeders over the 46 years we’ve lived here, and many winters none at all. But beginning in early December last year, blue jays started appearing in greater numbers, just as the cold and snow set in.

On December 16, with the thermometer at three degrees Fahrenheit, I counted 10 blue jays at our feeder area. From then until late January, numbers varied from seven to a high of 11 on January 16 when they blanketed the ground with their electric blue color.

Usually they stayed on the ground to feed, sparring with each other and the gray squirrels while the mourning doves and the smaller songbirds hung out in the periphery or visited the feeders, which, in turn were dominated by a pair of red-bellied woodpeckers.

A blue jay feeding with a red-bellied woodpecker in Danville, PA

A blue jay feeding with a red-bellied woodpecker in Danville, PA (Photo by fishhawk on Flickr, Creative Commons license)

At least some of the blue jays roosted in our Norway spruce grove and sounded their clarion “jay-jay” calls whenever I neared it on my daily walks. In mid-February, when blue jay numbers at the feeders had diminished, I found a trail of plucked blue jay feathers in the grove as well as plenty of “white wash” on the tree branches. I suspected a barred owl had been feasting on the blue jays, but whether it was death, the unseasonable warm weather, or some other reason, I last recorded five blue jays at the feeders on February 20 and then no more.

Despite being common birds that almost anyone can identify, these clever members of the Corvid family are not as easy to study as other corvids, such as American crows, because they are secretive and quiet during the spring and summer when they are courting, mating and raising their families.

But as acorns ripen on oak trees, these forest denizens announce their presence here, picking and eating acorns and beechnuts before they fall to the ground. Last autumn both the red and white oak complexes produced a huge crop of acorns, and no matter where I walked I could hear blue jays.

A blue jay with an acorn

A blue jay with an acorn (Photo by Tom Shockey on Flickr, Creative Commons license)

They also cache acorns to eat in the winter and spring, tucking two to three acorns in their expandable throat and upper esophagus, a fourth one in their mouth and a fifth in their bill and carrying them as far as a mile to cache in more open areas. They do the same with beechnuts.

Writing in The Second Atlas of Breeding Birds in Pennsylvania, Douglas Gross (Game Commission Endangered and Nongame Birds Section supervisor) calls the blue jay the “keystone bird of eastern deciduous and mixed forest of North America because of its habit of caching tree seeds, inadvertently planting deciduous trees, especially oaks and beeches…”

Like most caching birds, blue jays have excellent memories for where they hid their nuts, but a few are always missed. In Blacksburg, Virginia, researcher Susan Darley-Hill found that in 28 days approximately 50 blue jays carried and cached 150,000 acorns, which was 58% of the total nut crop from a mere 11 pin oak trees. Furthermore, they were capable of choosing sound acorns that had not been affected by weevil larvae.

Blue jay close-up with an acorn

Blue jay close-up with an acorn (Photo by Kenneth Cole Schneider on Flickr, Creative Commons license)

With those numbers, I can only imagine how many acorns blue jays transported from our forest last autumn. Still, I wondered if the huge crop of acorns was harvested by our resident blue jays or by those that had migrated from other areas.

Like most aspects of blue jays’ lives, their migration patterns are also puzzling. The northernmost subspecies of blue jays (Cyanocitta cristata bromia, our northern blue jay) lives as far north as Canada in the southern half of Ontario, Quebec, and New Brunswick. Sometimes northern blue jays may migrate south since thousands, moving in flocks from five to 250 birds, have been observed over the Great Lakes, including Lake Erie.

In Pennsylvania hawk watchers on our mountain ridges east of the Allegheny Front have reported migrating blue jays from the third week in August to the second week in November, although the greatest numbers migrate in mid-September to mid-October.

While blue jays winter in every Pennsylvania county, the jays are a mixture of resident and migrant birds. Researchers used to think that young jays were the migrants, but more recent studies show that jays of any age may migrate. Furthermore, it looks as if individual jays decide on a year to year basis whether to stay put or move south. Most likely it relates to either food sources, weather conditions or both.

A blue jay on a nest in Codorus State Park, Hanover, PA

A blue jay on a nest in Codorus State Park, Hanover, PA (Photo by Henry T. McLin on Flickr, Creative Commons license)

During spring in Pennsylvania blue jays migrate north from late April until mid-May. By the fourth of May, our resident blue jay males have already engaged in courtship displays with their monogamous partners, which continue as they select their nest sites and construct their nests. Usually they settle on a tree or bush as high as 25 feet from the ground, preferring an evergreen, but settling for whatever is available. They may even use rural mailboxes or occupy the nests of American robins.

Both sexes build their cup-shaped nest of twigs, small roots, moss, lichens and bark as well as human detritus such as light-colored tissue, cloth, paper, string, and wool. The male feeds the female as she sits on the three to seven bluish or light brown, spotted eggs for 17 to 18 days, beginning in late May in Pennsylvania. Then she broods her young for half their 17 to 21 days in the nest before she joins her mate in finding food for their offspring, although the male continues to provide most of the food.

A juvenile blue jay

A juvenile blue jay (Photo by Carolyn Lehrke on Flickr, Creative Commons license)

After their nestlings fledge, usually by July, the family remains together for another month or two. Then the young are on their own, while their parents sustain their bond for their lifetime.

Blue jays eat a wide variety of material including 22% insects during the breeding season. They are known for “anting,” rubbing ants against their feathers to remove the formic acid, not, as previously believed, to rid themselves of parasites, but so they can eat the ants, according to a recent study which found that 10 ants equals one egg in nutritional value.

Blue jays also consume human-based food—cultivated grains (especially corn) and fruit, bread, and dogfood—in addition to hard mast (43%) except in July and August. Their reputation for eating birds’ eggs and nestlings is highly overrated, and most studies put such food at one to two per cent of their diet if that.

Blue jays have their own predators to guard against. As adults they are the victims of Cooper’s, broad-winged and red-tailed hawks, great horned and barred owls and eastern screech-owls. Gray and fox squirrels kill and eat young fledglings, and nest predators include American and fish crows, squirrels, black rat and northern black racer snakes, raccoons and opossums.

Blue jays are known for their wide variety of calls and use them to mob hawks, large snakes, raccoons, domestic cats, and large owls. The video embedded below illustrates the variety of calls made by blue jays. These “songbirds without a song,” as Donald Kroodsma labeled them in his The Singing Life of Birds, use many sounds. After observing a pair on their nest near his home in Amherst, Massachusetts late in April, he noted that “the jays seem infinitely expressive, capable of transforming the simplest of jay sounds into a diverse array. At one extreme, the harsh ‘jay’ becomes a single, fine pure whistle, often with harmonics. Sometimes only one voice box will be engaged, sometimes two, creating special tonal effects.”

Altogether, in three and a half hours, he heard from those jays and others that visited them, five different ‘jay’ variations, two ‘squeaky-gate’ calls, melodious ‘bell calls’ and from the female on the nest ‘rattle’ calls.

“How little we know about these jays—that’s what my brief experience with them has taught me,” he concluded.

In Pennsylvania, blue jays increased from the first to the second atlasing periods with their highest numbers in Montgomery, Lehigh and Bucks counties in scattered woodlots. Because blue jays are able to adjust to changing land practices and airlift tree seeds to open areas, they will remain valuable “ecosystem engineers,” in the eastern United States by “increasing their caching effort after fires and selecting canopy gaps as cache sites,” according to a Cornell Lab press release of a study entitled “Jays and Crows Act as Ecosystem Engineers.”

Even renowned Philadelphia naturalist William Bartram, back in the early nineteenth century, recognized that blue jays “alone are capable, in a few years’ time, to replant all the cleared land.”