Bird Brains

Don’t call anyone a bird brain unless you are complimenting them. In the last couple decades, researchers worldwide have been discovering how amazing bird brains are. That should not be a surprise since feathered winged animals that fly have been evolving on earth for more than 150 million years, according to recent genetic analyses.

Neuroscientists Suzana Herculano-Houzel and Pavel Nemec recently published a paper entitled “Birds have Primate-like Numbers of Neurons in the Forebrain,” in which they write that the brains of birds are organized much like those of primates.

“We found that birds, especially songbirds and parrots, have surprisingly large neurons in their pallium: the part of the brain that corresponds to [our] cerebral cortex, which supports higher cognition functions such as planning for the future or finding patterns.”

To truly understand how intelligent birds are, researchers study how a species behaves in the wild, conduct experiments with captive birds, and compare what they see in the field with what they learn in the lab about a species’ genes and cells.

Some bird species seem to learn as little as possible to get along. Others are bird Einsteins. Most are in between. But relatively few of the more than 9000 species of birds worldwide have been studied in detail. And in much of the last century, even though people had been reporting anecdotally what appeared to be the intelligent actions of some birds such as crows and ravens, scientists had not begun any systematic studies of birds’ brains.

An American crow on a fence post

An American crow on a fence post (Photo by Joe McKenna on Flickr, Creative Commons license)

While some of us have watched parrots dance to music and New Caledonian crows solve problems on You Tube, many of our common birds are just as clever. American crows, for example, are adept at problem-solving. One researcher observed an American crow carrying water in a Frisbee to dampen its dried mash and another one using the end of a plastic slinky toy to scratch its head while it was perching.

According to research by John Marzluff in Washington State, American crows can recognize human faces, using the same parts of their brains to do this as we do. They plan ahead when they find and then leave a gift for a human who has been feeding them. In addition, they will delay gratification if they think they will be offered something better (usually food) at a later time.

Common ravens are socially adept, remembering other ravens they were friendly with before they paired for life, recalling those special friends even after they have been separated for three years.

A blue jay with an acorn

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

Still another member of the Corvid family, our blue jays, can accurately select fertile acorns 88% of the time and can count to five. They also mimic red-shouldered and red-tailed hawks. Blue jays often mimic the latter on our mountain and fool us. Some scientists hypothesize that they do this to trick other blue jays into thinking that there’s a raptor in the area and they need to leave, giving the blue jay imitating the red-tail time to harvest acorns without competition.

Another scientist noticed that a blue jay was smart enough to rub red ants on its body to get rid of the ants’ formic acid before eating them.

Because more than 80% of bird species are socially monogamous, staying with one partner for a season or even, in some cases, for life, they have developed “relationship intelligence,” which is an ability to understand what their partners want or need and respond in order to successfully breed and raise their young.

But apparently 90% of both sexes also sneak off to copulate with others without getting caught by their partners. This results in more healthy offspring.

In autumn, birds that store food for the winter, such as black-capped chickadees, grow new cells in their brain center (the hippocampus) which deals with spatial memory. This allows them to remember where they hid seeds months later.

A brown-headed cowbird female in Codorus State Park

A brown-headed cowbird female in Codorus State Park, near Hanover, Pennsylvania (Photo by Henry T. McLin on Flickr, Creative Commons license)

Brood parasites such as brown-headed cowbirds, especially the females, have large hippocampuses, because they are the ones that must lay their eggs in other species’ nests. They must find, remember, and revisit the nests they parasitize.

And invasive bird species, such as house sparrows and European starlings, have larger brains, are innovative, and have more flexible behavior because they must adapt to a foreign environment.

But our brainiest birds may be hummingbirds, because their brain is the largest brain relative to its size, a whopping 4.2% of their total body weight. Their hippocampus is five times larger than that of songbirds, seabirds and woodpeckers. They can remember every flower in their territory and how long it takes them to refill with nectar after they feed from them.

A ruby-throated hummingbird at a feeder

A ruby-throated hummingbird at a feeder (Photo by likeaduck on Flickr, Creative Commons license)

From year to year at home and in migration they also remember where every feeder is. They even learn which feeder people are responsible or irresponsible and have huge episodic memories that allow them to plan when and where to feed on hundreds of flowers a day.

The females watch older females making nests to learn how to do this because female hummers are on their own once they have bred. They must build their nests, brood their eggs, and feed their young alone.

Hummingbirds have the ability to move backwards, forwards, and sideways because they have more complex brains. In the part of their brain that responds to visual stimuli, instead of the usual back-to-front preference most animals and humans have, hummingbirds have no preference and can move in any direction.

A ruby-throated hummingbird at a flower

A ruby-throated hummingbird at a flower (Photo by chrisdupe on Flickr, Creative Commons license)

During their mating flights, which we’ve watched with awe from our front porch, they make instantaneous course corrections much faster than a fighter jet. Thus, their brains can move efficiently in three dimensions, which some scientists believe makes their tiny brains the most complicated of any vertebrate species.

Hummingbirds have not been considered songbirds, but biologists Claudio Mello and Erich Jarvis have found that hummingbirds have the same areas in their brains that control song learning and production as songbirds and parrots. They do sing in a higher pitch than songbirds, but their songs are amazingly rich, and in some species, complex.

Neurobiologists have been comparing birdsong with human speech and language. Like human children, young birds listen to other birds of their species to learn songs. They imitate and practice, seemingly using the same brain structures and genes to learn songs as children use to learn language. Some birds even stutter.

There is incredible variety in birdsong, as various as the 4,000 songbirds on our planet. And if you listen as carefully as Donald Kroodsma, who has been studying birdsong, especially in the eastern United States, for more than 40 years, you might be able to hear the 30 to 40 songs of a Carolina wren, the 50 to 100 of an eastern bluebird, the song and mimicking calls of a white-eyed vireo, the 30 to 40 songs of the ethereal wood thrush, the 200 to 400 different mimicking songs and calls of a gray catbird, the 100 songs of a northern mockingbird, and the 2,000 of the mimic champion—the brown thrasher.

Then there is the hermit thrush whose song has been compared to human musical scales with trills and slides reminiscent of a woodwind instrument. Some ornithologists have claimed that hermit thrushes sing major, minor and pentatonic (five note) scales.

But composer Emily Doolittle and biologist Tecumseh Fitch didn’t believe it. Still, using recordings of 14 hermit thrushes from the Borror Laboratory at Ohio State University, they started analyzing the pitches of 114 song types. When they slowed them down, they could hear their harmonies.

A hermit thrush singing

A hermit thrush singing (Photo by Yankech gary on Flickr, Creative Commons license)

“They jumped out at us,” Doolittle said, adding that 70% of the hermit thrushes’ songs were harmonic.

And maybe most miraculous of all to us are our songbirds that migrate. Scientists have found that at first they rely on genetic information for both direction and distance until they gain experience. Then they use their own brain maps to find their way. They build up magnetic maps during migration and some may use odor to help guide them. Some researchers even think they may hear a landscape infrasonically, especially the ocean, to help navigate. But to do all that and more they must possess fantastic spatial memories.

Every day, it seems, more is being revealed about the brains of birds. It’s a hot topic. For instance, researchers have recently found that the bird that is closest to its dinosaur ancestors is our own wild turkey. That’s because, since the days of feathered dinosaurs, the wild turkey’s chromosomes have had fewer changes than those of other birds. And, as any hunter knows, wild turkeys are wily and smart.

 

Thistle-Birds

In August our weedy First Field is alive with singing American goldfinches. Although most songbirds are finishing their parental duties by then, American goldfinches have barely begun.

A male American goldfinch among thistles at the John Heinz National Wildlife Refuge at Tinicum, PA

A male American goldfinch among thistles at the John Heinz National Wildlife Refuge at Tinicum, PA (Photo by Jim, the Photographer, on Flickr, Creative Commons license)

Their preference for thistle and other seeds may be one reason they wait until midsummer when the seeds are mature, because they line their nests with thistle, milkweed or burdock down and feed their nestlings a slurry of those regurgitated seeds, instead of insects, which are favored by spring-breeding birds.

Another reason may be the length and intensity of goldfinches unique prenuptial body molt in early spring. The dramatic change of the olive-buff males to vibrant gold bodies and black caps, which set off their black-and-white wings, never fails to dazzle me every April.

But knowing they do not breed until midsummer, I am also surprised that they sing as lustily as other species beginning in early spring. Some researchers believe that they form pair bonds in late winter flocks or as soon as both sexes arrive on their breeding grounds.

A female American goldfinch

A female American goldfinch (Photo by Eric Bégin on Flickr, Creative Commons license)

On the other hand, males need to try harder for mates because for every 1.6 males, there is only one female, so first-year males have a difficult time acquiring a mate. Thus, while goldfinches are mostly monogamous, at least 15% of females mate with a second mate especially if they have a second brood.

Back in the years 1979 until 1985, Alex L. Middleton, of the University of Guelph in Ontario, was watching nests of goldfinches he had color-banded on the university grounds. That was when he made, for the first time in ornithological history, the observation that the goldfinch father of the first brood was not always the father of the second one, proving that regular and recurring classical polyandry was occurring in a passerine species.

A male American goldfinch at the John Heinz National Wildlife Refuge at Tinicum, PA

A male American goldfinch at the John Heinz National Wildlife Refuge at Tinicum, PA (Photo by Jim, the Photographer, on Flickr, Creative Commons license)

During his study, he found five cases of polyandry and concluded that even though only a few females practiced it, they had more than seven fledglings a season compared with slightly over three for “faithful” females. In addition, the polyandrous females were older, experienced birds that preferred to breed with older males because of their experience and their physiological fitness which enabled them to start breeding a week ahead of younger males.

But a younger male sometimes attached itself to the breeding pair and when the first male was still busy feeding his first brood and his mate was already building a second nest, the surplus male bred with the female. Since then, researchers have been finding that many so-called monogamous songbirds are not as faithful as they were once portrayed with both males and females sneaking extra-pair copulations.

A crowd of American goldfinches on a Nyjer thistle feeder in Danville, PA

A crowd of American goldfinches on a Nyjer thistle feeder in Danville, PA (Photo by fishhawk on Flickr, Creative Commons license)

Last April our feeders were crowded with males in the midst of molting and far fewer females. Whether they were migrant males and females or those that had been with us all winter was impossible to tell, because we had had on average 12 goldfinches at a time on our feeders throughout the colder months.

Here in Pennsylvania they migrate through the state from late March until late May, although their peak migration is from the fourth week in April to the second week in May. Many are coming from as far south as the Gulf states and Florida in the United States and central Mexico, but they do wander in large flocks wherever there is ample food, even in winter. They breed from southern Canada through most of the United States with the exception of the southwest and along the Gulf Coast.

American goldfinches rarely nest in Pennsylvania before July 5 and nests with eggs are found here through the end of August. However, the earliest confirmed breeding in the commonwealth, according to the Second Atlas of Breeding Birds in Pennsylvania, was that of a bird carrying nesting material on May 2 and the latest was of parents feeding young on October 14.

The female selects the nest site, often in a wet corner of a brushy pasture such as our First Field, and constructs it in the fork of a sapling or shrub, anywhere from one to 33 feet above the ground. Three dogwood species and numerous hawthorn and willow species are special favorites.

She takes at least four days to build her tightly constructed nest with walls so thick that the nest can hold water. Sometimes this leads to disaster during heavy rainstorms when unattended nestlings drown.

A male American goldfinch feeding a female on May 4, 2007

A male American goldfinch feeding a female on May 4, 2007 (Photo by Doug Greenberg on Flickr, Creative Commons license)

One unusual nest was found hanging from a broken cornstalk in a cornfield near Hamburg, Pennsylvania on September 24, 2008. It was turned on its side on the stalk and was attached by spider silk and plant fibers. Lined with thistle down, it contained a single egg. Even though American goldfinches have been known to nest in as many as 87 plant species, this was the first nesting on a cornstalk confirmed with a photograph. But after watching for a couple days and seeing no goldfinches nearby, the researchers concluded that the nest had been abandoned several weeks before, especially since the nest looked a bit tattered.

Once their nest is finished, the pair leaves the area for several days, maybe to deter predators such as eastern garter snakes, blue jays, and short-tailed weasels. Then the female lays four to six very pale bluish-white eggs and she sits on the nest 95% of the time incubating the eggs while her mate supplies almost all of her food.

The male often sings and flies high above the nest site, checking up on whether his mate needs food. When he hears her soft teeteeteetee hunger call, he drops down near the nest. Then she furtively hops through the underbrush to him to receive her meal.

After 12 to 14 days, the eggs hatch and she broods the young while the male continues feeding her on the nest. She in turn feeds the chicks, but after four days she leaves the nest. Then both parents feed their nestlings by regurgitating a sticky, half solid mass of seeds, including those of sunflower, thistle, burdock, dandelion, chicory, aster and goldenrod, all of which thrive in overgrown pastures.

The nestlings are quiet during their first week in the nest, but by the second week they are active and noisy and fledge anywhere from 12 to 17 days of age. They are dependent on their parents for three more weeks while they learn what to eat and where to find it.

Once they are independent, the young birds join flocks of adults that increase in size during late summer and early autumn. It is then that goldfinches, once they finish breeding, engage in their second molt of the season that lasts as long as 75 days.

They also wander the countryside in search of food. Their choices have led to a variety of nicknames such as “catnip-bird,” “beet-bird,” “lettuce-bird,” and “thistle-bird,” that attest to their liking of both garden and wild plant seeds. “Wild-canary” and “shiner” are tributes to the male’s golden plumage. In addition, their genus name, Carduelis, is Latin for “thistle” and their species name, tristis, means sad, referring to their plaintive calls. Their song, which is unusually long, is both rambling and warbling.

An American goldfinch in Chester County, PA

An American goldfinch in Chester County, PA (Photo by Kelly Colgan Azar on Flickr, Creative Commons license)

American goldfinch numbers are holding steady in the commonwealth, as they nested in 96% of the atlasing blocks with the highest numbers in suburban and rural developments, places that have both wild and garden foods as well as year around, amply stocked birdfeeders. In addition to weedy fields and suburban gardens, goldfinches also like river flood plains, early second growth forest, and orchards for nesting and food.

It is encouraging to learn that one of North America’s most attractive and appealing birds—“panoplied in jet and gold” as ornithologist Edward Howe Forbush once wrote, has benefited rather than suffered from humanity’s actions.

So, the next time your neighbors complain about the dandelions in your lawn or weeds in your garden, tell them you are growing food for American goldfinches.

 

Adaptation

July, like January, is the most extreme month of its season, and during both months I must adapt to challenging weather if I want to walk our trails and observe wildlife.

Black birches in the forest of Plummer’s Hollow

Black birches in the forest of Plummer’s Hollow (Photo by Dave Bonta on Flickr)

In January, when the wind is howling and it’s ten degrees Fahrenheit, I wait until mid-morning to venture outside swathed in several layers of clothes.

In July I try to be abroad by 8:30 a.m. dressed in as little as possible. That used to mean shorts and a tank top, but since ticks arrived on our mountain, I pull on long, beige-colored, Permethrin-soaked pants, which I tuck into light-colored socks, and a long-sleeved shirt over a tank top. Then, I put a wide-brimmed hat over my short hair and I’m off.

But last July the heat and humidity on many days was more debilitating than usual. Even 8:30 was too late on many July days for someone as heat-averse as I am.

The morning sun through the fog over the First Field

The morning sun through the fog over the First Field (Photo by Dave Bonta on Flickr)

We’ve been told that humans, plants, and wildlife must adjust to our changing climate. In that spirit my husband Bruce suggested I get up at 5:00 a.m., grab a cup of coffee, and go, instead of rising an hour later, preparing and eating breakfast, and following my normal hour of back and neck exercises before venturing outside.

That’s how I became a connoisseur of sunrises. Most dawns I rushed the quarter mile up to the spruce grove and Alan’s Bench at the top of Sapsucker Ridge. One morning the sky was golden and lit up the trees along the trail. On another, a rosy-fingered dawn predicted a clear, hot day ahead.

Near the end of July I watched the sky turn from gold to rose and finally pink before I reached Alan’s Bench. A sudden light flashed on the horizon as the sun appeared over Nittany Mountain, heralded by the drumbeat of a pileated woodpecker and the “witchedy, witchedy” of a common yellowthroat. As soon as it crested the mountain, I looked away from that burning eye that makes life on earth possible.

An ovenbird in Chester County, PA

An ovenbird in Chester County, PA (Photo by Kelly Colgan Azar in Flickr, Creative Commons license)

Instead, I sought the sanctuary of the forest as it filtered the fierce light through its green film of leaves.

Although birdsong dwindles in July, I listened to the dawn singing and calling of ovenbirds, red-eyed vireos, scarlet tanagers, eastern towhees, Acadian flycatchers, eastern wood-pewees, hooded and black-throated green warblers in the forest and common yellowthroats, song and field sparrows, indigo buntings, northern cardinals, Carolina wrens, cedar waxwings, and gray catbirds in the fields and yard.

One charmed morning I was serenaded by a chorus of wood thrushes as I walked down our road. The thrush music echoed in the outdoor cathedral of hundred-year-old trees looming overhead. I gave a silent prayer of thanks for their songs and hoped I would live to hear them another year. (I will embed a brief YouTube video of a singing wood thrush.)

On that same dawn walk I startled two does and two fawns that were standing in our stream. The fawns disappeared up the road bank while the does remained watching me for a few seconds before following their offspring.

A black rat snake

A black rat snake (Photo by Tom Walsh in Wikimedia, Creative Commons license)

I also found a black rat snake sprawled across the road. At first I thought it was dead, but as I stood above it and suggested it get off the road, it twitched its tail and curled up, looking as fierce as it could manage. I stepped carefully around it and continued on my way. Later, after the sun’s red disk shone through the trees and I retraced my steps, the snake had vanished.

Not all days were steamy. Early in the month, I devoted several cooler mornings to taking our 11-year-old granddaughter Elanor on our longer trails, several of which she had never hiked, before she and her parents set off for new lives in Arizona. I didn’t want her to forget the green lushness of a Pennsylvania summer. On one such walk, several almost grown turkey poults flew up in front of us. On another I pointed out blooming rhododendron, wild hydrangea, wood nettle and black cohosh along the road.

But Elanor was most impressed by the abundance of baby cottontail rabbits and adults in our yard, especially one attracted to our veranda. In fact, its cement floor proved to be alluring to a variety of small mammals including chipmunks that seemed affronted by Bruce and my sedentary presence on the veranda.

A long-tailed weasel

A long-tailed weasel (Photo by Bryant Olsen on Flickr, Creative Commons license)

We grew accustomed to sitting on our veranda chairs without speaking or moving as rabbits and chipmunks crept closer and closer. One morning, after I returned from my walk at 6:30, we sat there silently gazing at First Field. A long-tailed weasel emerged from beneath a forsythia bush next to the veranda and started toward the chipmunk burrow in the lawn at the far end of the veranda. When I turned to Bruce to see if he noticed the weasel, it dashed back the way it had come.

We remained silent, and a few seconds later, it ran on to the end of the veranda. Again I turned to Bruce and again the weasel retraced its steps. This time it didn’t come back. Bruce didn’t see it either time, but I even glimpsed its white underparts the second time around. This happened the day after my birthday, and I was grateful for my belated gift of a brief moment with an elusive creature.

Four eastern phoebe chicks in their nest

Four eastern phoebe chicks in their nest (Photo by jeffreyw on Flickr, Creative Commons license)

On our front porch a pair of eastern phoebes had built their second nest. One early July evening, while Elanor was eating dinner with us on the porch, the four nestlings became four fledglings as one after the other flew over our heads chirping.

Even our back porch was attractive to wildlife. One night I left a planter of house plants I had washed out on the porch to dry. The next morning I found a hole dug in the dirt and muddy raccoon prints on the porch floor.

And of course we had our usual bear sightings. Early in the month our son Steve, driving up our road in the afternoon, had a young cub run in front of his car halfway up the mountain. Near the end of the month, as I reached the top of Sapsucker Ridge, I heard a crash from a tree and caught a glimpse of a bear running downslope toward the interstate.

These glimpses I have of the lives of wild animals and birds are often tantalizing and sometimes I can only guess at their intentions. But I did solve one mystery and its perpetrators.

Norway spruce cones, including one in the lower right on which part of the cone scales have been removed

Norway spruce cones, including one in the lower right on which part of the cone scales have been removed (Photo from the Plant Image Library in Flickr, Creative Commons license)

One hot, humid morning inside the Norway spruce grove, I noticed dozens of still-immature spruce cones that had been clipped from the tops of the tallest trees and stripped of their overlapping cone scales. The scales lay in golden-beige heaps at the base of the trees.

Never before had I seen this even though the trees have had mature cones for years. But the acorn crop had failed for two years and I suspected hungry gray squirrels were after the two seeds at the base of each scale. Fourteen days later I spotted a gray squirrel climbing up a cone-laden spruce tree, proving to my satisfaction that they were producing the piles and scatterings of diamond-shaped cone scales throughout the grove.

Later, I read in North American Tree Squirrels by Michael A. Steele and John L. Koprowski about a study they did in North Carolina of longleaf pine cones. They found that even though the cones of most conifers don’t fully mature until October, they are already nutritious by late July when squirrels sometimes have little else to eat. The North Carolina fox squirrels stripped the longleaf cones the same way our gray squirrels had stripped the Norway spruce cones, by starting at the bottom of a cone and rotating it like an ear of corn as it gnawed off one cone scale at a time.

At the end of the month, after a much-awaited rainstorm the previous evening, I walked Laurel Ridge Trail listening to the same but much quieter suite of singing birds—scarlet tanager, eastern wood-pewee, and red-eyed vireo. I picked up a bird’s nest lined with thin stems and plastered with lichens. The exquisite little nest had blown from a high tree branch in the storm and had been constructed by an eastern wood-pewee.

Later, as I approached our yard, I noticed a male American goldfinch crying on and on from our electric line. Then a large raptor lifted off a yard tree and landed on a low black walnut branch. It was an immature Cooper’s hawk still peering around in search of prey and providing a close look at the white streaks above its eyes and its reddish breast and belly.

As soon as the hawk flew off, the goldfinch was quiet, and a gray catbird and several other birds began calling as if giving an all-clear signal.

July may often be an uncomfortable month to be outside, but my many glimpses of wildlife make every sweaty, buggy walk worth the effort.

 

 

Great Crested Flycatchers

On a lovely morning in late June, I watched a pair of great crested flycatchers calling back and forth. One was in our side yard and the other in our front yard.

A great crested flycatcher in Missouri

A great crested flycatcher in Missouri (Photo by Andy Reago & Chrissy McClarren in Wikimedia, Creative Commons license)

Then both of them landed on a black walnut tree beside our driveway and appeared to be interested in a deserted woodpecker hole. Still, it seemed a bit late for them to be seeking a nest hole unless their first nesting attempt was foiled by a predator. Eventually, they flew away, still calling their raucous “wheep, wheep.”

Flycatchers are not true songbirds but belong to a closely related line that have brains unable to imitate songs. They are born with genetically predetermined calls and voice boxes simpler than those of songbirds. Thus most of us hear only their “wheeps,” “rasps,” and a rapid series of “whits,” the latter reminiscent of a policeman’s whistle. A two-minute YouTube video shows a great crested flycatcher calling.

But W. John Smith and Anne Marie Smith studied the vocalizations of great crested flycatchers in southeastern Pennsylvania and discovered at least 12 different calls which related to their behavior during breeding and even on their wintering grounds in southern Mexico, Central America and northwestern South America. They found that the flycatchers were particularly adept at using their vocalizations to manage their social behavior. Mated pairs duetted and males defended their territories by vocalizing as they approached their shared territorial borders

Donald Kroodsma, who is an expert in birdsong, describes the dawn song of one great crested flycatcher male as “an emphatic ‘wheeee-up,’ followed by another, then a faint low, buzzy note, barely audible, the pattern repeating. I can hear how successive ‘wheeee-up’ songs are different, as he plays with duration, frequency, emphasis, tone quality, and more—like snowflakes, no two ever quite alike,” he writes in his book Listening to a Continent Sing.

A great crested flycatcher in Florida

A great crested flycatcher in Florida (Photo by Andrea Westmoreland in Wikimedia, Creative Commons license)

One of nine breeding flycatchers in Pennsylvania, most, such as the eastern phoebe, eastern wood pewee, Acadian and least flycatchers, are variations on gray and white, and some are most easily identified by their distinctive calls. However, great crested flycatchers are not only noisier than the others but showier with lemon-yellow bellies, gray heads, throats and upper breasts, and long, reddish-brown tails that glow in the sunlight. When excited they erect their crown feathers to form crests, hence their common name.

Unlike other tyrant flycatchers, so-called because they pursue and capture prey in flight, great crested flycatchers also glean insects from vegetation. In addition, they are the only cavity-nesting flycatchers in eastern North America.

A great crested flycatcher using a nest box

A great crested flycatcher using a nest box (Photo by vladeb on Flickr, Creative Commons license)

Those cavities include natural openings in trees, abandoned woodpecker holes, hollow posts, and even nesting boxes, as well as more bizarre choices such as a cannon at Gettysburg National Park, an old wooden pump, stove pipe or open gutter pipe, old boxes or tin cans. But a recent study of great crested flycatchers’ nests in Florida found that the higher off the ground the nests were, the more likely they were to fledge young.

That study also reported that those flycatchers preferred to nest in abandoned woodpecker nests, particularly those of red-bellied woodpeckers. Of the 44 nests the Florida researchers surveyed, 20 were in old red-bellied woodpecker holes. Furthermore, contrary to earlier studies, those great crested flycatchers had less interest in nesting in naturally occurring hollows in live trees.

The great crested flycatcher likes to nest in a mixed deciduous forest

The great crested flycatcher likes to nest in a mixed deciduous forest (Photo by fishhawk on Flickr, Creative Commons license)

Great crested flycatchers are summer residents throughout eastern North America east of the Great Plains, from southern Canada to the Gulf States. They like to nest in mixed deciduous forests, but will make do in human-constructed places such as orchards, gardens, or golf courses.

Here on our mountain the males return from their wintering grounds in late April or early May, a week or more ahead of the females. Most of them return to the same area year after year and occasionally have the same mates. The males establish their territories by clashing with their competitors. Dr. Samuel Dicky, writing from the backwoods of West Virginia where he watched great crested flycatchers for more than 30 years, observed (as quoted by Arthur Cleveland Bent, Life Histories of North American Flycatchers, Larks, Swallows, and Their Allies, p.107) that “males were seen to clash…where the natural habitats of pairs overlapped. They then would draw up close to one another…expand their wings, spread their tails, and dart rapidly at each other. Then they tore some feathers from breasts, held fast with their claws, and tossed and tumbled on the ground.”

Once the females arrive, the males spend their time chasing and copulating with them. They also follow their mates closely during nest-building and egg-laying to make sure they are not cuckolded. Nests in Pennsylvania are built in May and early June. After pairs choose their nesting cavity, the female fills it with a wide variety of materials from leaves, seed pods, and grass to the hair of domestic and wild animals, feathers of native birds and poultry, and bits of bark, cloth, and paper, making them packrats of the avian world.

Almost every great crested flycatcher nest has a shed snakeskin, often left hanging outside the cavity, and lacking that, items of similar texture—cellophane, plastic wrappers, onion skins, or thin paper. Why they do this has been debated for years. Since not all nests have snakeskin, many researchers think the birds don’t recognize what they have and like the texture. Others believe that they are used to deter nest predators, but surely not snakes because they are major predators on their eggs and nestlings especially black rat snakes.

Recently, researchers in Arkansas found that the presence of snakeskin in nest boxes deterred mammalian predators, particularly southern flying squirrels. And nest boxes without snakeskin were preyed on by those squirrels. That seems to settle the question, at least in Arkansas.

A yellow-throated vireo

A yellow-throated vireo (Photo by Matt Tillett on Flickr, Creative Commons license)

Once the nest is built, both parents defend it and the surrounding area, attacking small mammals and most birds, which may be why I observed one May day a great crested flycatcher attack a singing, flying yellow-throated vireo in our yard, only my second sighting ever of that vireo species on our mountain. They tumbled earthward before the flycatcher flew one direction and the vireo the other.

Great crested flycatchers are feisty birds. Florida ornithologists watched them attack most birds near their nests from Carolina wrens to European starlings and even woodpeckers, including northern flickers. Once one even went after a black rat snake that had eaten its nestlings, yelling so loud that it attracted a northern mockingbird, blue jay, and northern cardinals that added their cries to those of the flycatcher.

The female great crested flycatcher incubates her four to eight, heavily splotched, yellowish or pinkish-white eggs while her mate continues to guard her and the nest. After 13 to 15 days, their eggs hatch and the young spend another two weeks in the nest. Both parents feed them, although the female is the primary breadwinner.

A great crested flycatcher preparing to feed an insect to its young in the cavity below

A great crested flycatcher preparing to feed an insect to its young in the cavity below (Photo by Bruce Bodjack on Flickr, Creative Commons license)

The nestlings eat the same variety of insects the adults do, namely butterflies, moths, beetles, grasshoppers, crickets, stinkbugs, flies, bees, wasps and dragonflies. But the parents will crush the larger insects in their mandibles before feeding them to their nestlings. They also give them spiders and small wild fruits.

When they fledge, at 13 to 15 days old, the family stays together for three more weeks. The parents continue to feed them with diminishing frequency. They also defend their fledglings.

By midsummer I no longer hear the strident calls of the great crested flycatchers. And in September they are heading south.

Because they are edge species and able to adapt to nest boxes, they are still common throughout their breeding range. Here they increased in southeastern Pennsylvania from the first breeding bird atlas, when they were detected in 73% of the atlasing blocks, to the second atlas when they were found in 89% of the blocks. Roy A. Ickes, writing in the Second Atlas of Breeding Birds in Pennsylvania, theorizes that the birds “may benefit from the increased number of dead trees and canopy gaps associated with adelgid infestation” that has killed most of the hemlocks.

But great crested flycatchers remain most abundant in the ridge and valley, lower Susquehanna Valley, and north western corner of the state. They also live in forested residential areas around lakes. But even though they are still widespread here with about 192,000 birds during the season, their population declined an estimated 32% in the two decades between the first (1983-1988) and second (2004-2009) breeding atlases.

We can only hope that this loudest and showiest member of the flycatcher family will continue to adapt in the future to the human-caused changes in their increasingly fragmented habitat.