The Life of a Sapsucker

Last November26, I walked into our sunroom. Almost immediately I spotted a male yellow-bellied sapsucker eating the fruit of one of two hackberry trees we had planted more than a decade ago. Also called “sugarberry,” it is known to be a favorite winter food for a variety of songbirds, most notably American robins and yellow-bellied sapsuckers.

A portrait of a male yellow-bellied sapsucker

A portrait of a male yellow-bellied sapsucker (Photo by Claudine Lamothe on Flickr, Creative Commons license)

I had a bird’s eye view of this unusual woodpecker from our sunroom, which is perched on a hillock surrounded by black walnuts, black locusts, scarlet oaks, and a white pine. As I watched the sapsucker, he plucked and ate several hackberries and then flew down into the dead middle tree of the three large front yard black locusts and tapped away.

Next he flew to a black walnut tree branch outside the sunroom and probed in a crevice. Every time he withdrew his bill he had food in it that he swallowed so he was probably searching for and eating insects. Finally, he hitched his way past the crevice and began drilling small sap holes, but after a couple minutes he flew away.

As close as I had been to the sapsucker, I could not be certain what he was doing once he left the hackberry tree, but I could verify his attraction to hackberries. Since the weather had been mild, he was lingering later than the usual sapsucker migration period in Pennsylvania of late September through October. Or perhaps he planned to stay for the winter on our 1500-foot mountaintop as an occasional sapsucker has in the 47 years we’ve lived here.

A wintering yellow-bellied sapsucker alongside the Schuylkill River Trail, Chester County, PA

A wintering yellow-bellied sapsucker alongside the Schuylkill River Trail, Chester County, PA (Photo taken by Brian Henderson on Feb. 21, 2016, and posted on Flickr, Creative Commons license)

Male yellow-bellied sapsuckers don’t migrate as far south as the females, although most yellow-bellied sapsuckers migrate from their northern nesting grounds of southeast Alaska, the southern half of Canada, and our northern states where they breed as far south in the east as Pennsylvania’s northern tier. A few winter mostly in the southern part of the commonwealth, but the yellow-bellied sapsucker—the only woodpecker species in eastern North America that is completely migratory—usually spends its winter farther south in the United States, West Indies, Mexico or Central America.

As their name suggests, both the male and female yellow-bellied sapsuckers have dull, yellow bellies and breasts in addition to red crowns and black faces, wings, and backs accented by white patterning—two horizontal stripes on their faces, a broad patch on each wing, and stippling on their backs. But only the males have flaming red throats.

Because they sapsuck, they are nicknamed “sap-sippers” and “sup-saps,” and lap up leaking sap and any trapped insects with their specialized, brush-tipped tongues. Although they have drilled their sap wells in more than 1000 tree and woody plant species, they prefer sick or wounded paper and yellow birches, red and sugar maples and hickories, all of which have high sugar concentrations in their sap.

A yellow-bellied sapsucker on a tree with rows of holes

A yellow-bellied sapsucker on a tree with rows of holes (Photo by Vitalii Khustochka on Flickr, Creative Commons license)

In early spring they drill holes in xylem, the inner part of the trees, to obtain sap moving up the branches, but after trees leaf out, they drill shallow, rectangular wells in phloem, the part of the tree that carries sap down from the leaves. That sap may be 10% sugar and feeds not only sapsuckers but ruby-throated hummingbirds, which time their migration to that of sapsuckers to make use of this abundant resource. Tufted titmice, white-breasted nuthatches, black-capped chickadees, red-bellied and downy woodpeckers, and black-throated blue warblers have also sampled the flowing sap as well as bald-faced hornets, paper wasps, chipmunks, red squirrels, bats, porcupines, and martens.

While sap comprises about 20% of their yearly diet, they also eat a wide variety of insects, not only those trapped in the sap, but those they pry from under bark scales and catch in the air. Bast, the inner bark and cambium layers of trees, fruit, including berries of dogwood, black alder, Virginia creeper and wild black cherries, buds (in spring) and seeds complete their varied yearly diet.

Yellow-bellied sapsuckers begin returning to Pennsylvania by the third or fourth week in March. Here on our ridge-and-valley mountain, I first know they are back when I hear their peculiar mewing alarm calls sometime in early April. Then I find them quietly tapping and tippling in our woods. Usually they are males because they migrate a week ahead of the females. And here they seem to favor hickory trees which are already scarred with rows of old sapsucker holes. Hickory trees, it turns out, have a sap flow with a sugar concentration of between 6.4% and 11.1%.

A yellow-bellied sapsucker that returned to Pennsylvania

A yellow-bellied sapsucker that returned to Pennsylvania (Photo by Henry T. McLin in Codorus State Park, April 16, 2013 on Flickr, Creative Commons license)

One April day I watched two males flying at each other around a medium-sized hickory tree, fighting over possession of a favorite tippling tree. I settled down to watch as one quickly routed the other and started to “sap-sip.” He braced his tail against the tree at a 45 degree angle, gripped the bark with his feet, and dipped his beak into each hole two or three times. Each time he withdrew his bill it glistened with sap. Twice he had to stop and defend the tree from the other sapsucker before both birds flew off.

On another April day I watched a male sapsucker sipping sap from a huge old sugar maple tree above the Far Field Road. That tree had old and new sapsucker holes, and he drilled new ones as I watched, The flowing sap also fed flies but instead of eating them, he made a quick dive to the ground, plucked up an insect, and flew back to his original perch.

He occasionally glanced at me as I sat on the ground six feet away, but he continued his drilling and sipping. The latter he did by turning his head sideways and dipping his beak into each hole two or three times, being careful not to touch the sticky bark with any other part of his body except his feet and the tip of his tail.

Insects in the beak of a male yellow-bellied sapsucker

Insects in the beak of a male yellow-bellied sapsucker (Photo by ramendan on Flickr, Creative Commons license)

He also defecated a fine stream every three minutes by quickly lifting his tail away from the bark and squirting a good foot or so from the tree. In his Woodpeckers of Eastern North America, Lawrence Kilham wrote of watching a sapsucker drilling in a black walnut tree during a January thaw in Washington, D.C. He noted that in a 25 minute period, one sapsucker voided 11 times or once every two minutes.

I didn’t hear the distinctive irregular drumming of a sapsucker. Mostly they drum on their breeding grounds to defend their territory and especially their sapsucking sites. Here in Pennsylvania they breed in the forests of our northern tier with 44% of our state’s estimated 96,000 birds in Warren, McKean, Potter and Tioga counties alone.

According to biologist Bernd Heinrich in his One Wild Bird at a Time, “the male drumming attracts the female, and that when she arrives he leads her to his previously found nest site [in a tree with hardwood decay fungus]. If she approves, she lets him know by offering token help, and then he begins excavating in earnest.”

A male yellow-bellied sapsucker checking out a potential nest hole

A male yellow-bellied sapsucker checking out a potential nest hole (Photo by Keith Williams on Flickr, Creative Commons license)

Sapsuckers are monogamous during their breeding time and often from year to year because they frequently return to the same breeding site, tree, and even cavity as the previous year. While he takes two to three weeks to drill a new nest cavity, she spends her time preening and resting. The entrance hole is a tight 1.5 inches and the nest cavity as deep as 10 inches.

She lays five to seven white eggs on a bed of wood chips left over from cavity construction and both parents incubate them with the male taking on some of the day hours in addition to the night shift. After 10 to 13 days, the naked hatchings emerge. The parents take turns brooding their young and feeding them insects often coated in sap.

Most nests are 9.8 to 45.9 feet from the ground and the nestlings are noisy which may attract predators. Kilham reported weasel predation in nests he observed in New Hampshire. Other predators include raccoons, snakes, red squirrels, hawks and black bears.

An immature yellow-bellied sapsucker

An immature yellow-bellied sapsucker (Photo by Kenneth Cole Schneider on Flickr, Creative Commons license)

At 25 to 30 days old, the young fledge but continue with their parents who feed them for a week and teach them sapsucking. The fledglings quickly learn to capture insects in the sap wells, but even after they feed themselves, they keep in vocal contact with their parents and use their sap wells. About six weeks out of the nest, they can drill their own sap wells but appear to stay in family groups at least until migration.

Yellow-bellied sapsuckers have been increasing throughout their range according to the 2011 Breeding Bird Survey. In Pennsylvania between the first and second breeding bird atlasing, breeding increased 99 percent Scott H. Stoleson reported in the Second Atlas of Breeding Birds in Pennsylvania. Although sapsuckers did not increase in the Allegheny Mountains where they once bred, they filled in and expanded in the northern, eastern, and western sections of Pennsylvania. Thus we can rejoice that such a unique woodpecker thrives in the commonwealth.

A Madness in the Sky

Sometime in late October or early November I hear and then see enormous blackbird flocks as they briefly land in our forest calling and feeding. Usually they consist of incredibly noisy European starlings and common grackles on their way South for the winter. I enjoy watching and listening to them as they engage in what scientists call “cluster flocking” or “collective animal behavior,” terms which include schools of fish, swarms of insects, flocks of birds, and herds of mammals.

A starling murmuration in Illinois

A starling murmuration in Illinois (Photo by Dan Dzurisin on Flickr, Creative Commons license)

But none are more spectacular that the murmuration flights of European starlings, described by Grainger Hunt, a senior scientist at The Peregrine Fund, as “a dazzling cloud, swirling, pulsating, drawing together to the thinnest waist, then wildly twisting in pulses of enlargement and diminution, a fluid choreography of funnels, ribbons, and hourglasses, spills and mixing, ever in motion.”

European starlings are an invasive species, brought over from England in 1880 by well-meaning Shakespeare enthusiasts who wanted to fill American skies with every bird species mentioned by the bard. But many Americans regard them as pests. In contrast, Europeans have appreciated murmurations for a very long time. And judging by the popular You Tube murmuration video shot over the River Shannon in Ireland, not only Europeans but Americans and nature appreciators throughout the world have been wowed by the phenomenon.

Even bird-oriented magazines such as Living Bird and Audubon have featured stories and photos of murmurations, although the latter was taken to task by one reader for glorifying the invasive species, admitting that the photos were “spectacular” but the birds themselves “a scourge,” that had perpetrated “extreme damage on North American ecosystems…”

A European starling

A European starling (Photo by PierreSelim in Wikimedia, Creative Commons license)

That may be true but everyone from poets to the publisher of The Christian Century have been inspired by murmurations they have witnessed in the United States. Poet Barbara Crooker in her poem “Murmuration” describes “the gray silk sky embroidered with black kisses” and “an immense river of noise.” That noise, produced by multiple wingbeats, is why the phenomenon is called a “murmuration.”

Publisher Peter W. Marty writes that their “synchronized movements look like a magic carpet rippling and rolling through the sky” and remind him of the musical term “legato,” because it “has a curved line above the phrase to indicate that it is to be sung or played in a flowing manner.”

A murmuration of starlings by Edmund Selous in his book Bird Life Glimpses (1905, p.129, in the public domain)

Scientists too have been intrigued and puzzled by starling murmuration. Dozens and dozens of papers have been written speculating on the how and why of murmuration beginning with the British naturalist Edmund Selous who, in his 1905 paper, called it “a madness in the sky.” After 30 years of studying murmuration and other flocking by birds, he thought that only the threat from a predator, such as a peregrine falcon, or “a kind of telepathy between the birds,” what he called “thought transference” could be responsible.

Another scientist, Wayne Potts, a biologist at Utah State University, came up with what he called “The Chorus Line Hypothesis” by filming the so-called “dance of the dunlins,” which is similar to the murmuration of starlings. He found that the wave from one bird to another moved twice as fast as a human’s visual reaction time and concluded that each bird must anticipate the spreading wave and react before it gets there.

Then the age of computers attracted the interest, not only of biologists and ornithologists but engineers, physicists, and physicians. They hoped to use an understanding of flocking behavior to predict bird strikes on aircraft, to figure out traffic patterns on highways, to comprehend particle swarms and how crystals form, and to gain knowledge about how our brains operate, for example. Some even hoped to use what they learned to understand crowd psychology in humans.

Craig Reynolds’ diagram of the computer model of “Boids” flocking behavior, which he describes as following three steering behaviors: top to bottom, separation (steering to avoid crowding), alignment (steering with the average direction of the flock) and cohesion (steering toward the average positions of other birds in the flock). The Wikipedia states that since these images are simple geometry, they are in the public domain.

Craig Reynolds’ diagram of the computer model of “Boids” flocking behavior, which he describes as following three steering behaviors: top to bottom, separation (steering to avoid crowding), alignment (steering with the average direction of the flock) and cohesion (steering toward the average positions of other birds in the flock). The Wikipedia states that since these images are simple geometry, they are in the public domain.

In 1987 software designer Craig Reynolds developed a program called “Boids” of virtual birds based on his observations of blackbird flocks in a nearby California cemetery. He programmed each computer “boid” to follow three rules: avoid collisions, fly at the same speed, and move in the same direction. Scientists interested in collective robotics and crowd modeling, for instance, have cited his work.

But movie buffs should know that the computer-generated swarms of bats and armies of penguins marching and flying in The Batman Returns, as well as battle scenes in The Lord of the Rings and Hobbit films used a software program similar to “Boids.” And Reynolds, in 1998, received an Academy Award for his “Boid’s” design and its importance to film animation.

Beginning in this century numerous studies have continued the search for the how and why of murmuration using computer simulations and citizen science.

First there was STARFLAG—Starlings in Flight—which was a study by European physicists, economists, and biologists from 2004-2007. Using cameras that took photos of 3000 starlings swarming over Rome’s Termini railroad station from two different angles, they discovered that the spatial relationship of flocking birds is based on the position of six or seven nearby birds and that this so-called topological interaction remains the same no matter how large or close the birds are to one another. This allows them to “change shape, fluctuate and even split, yet maintain the same degree of cohesion [because] information moves across the flock very quickly, and with nearly no degradation,” the 12 authors of the study concluded.

Thus starlings can respond to what others are sensing from one side of the flock to another almost simultaneously and evade predators.

Although that seems to answer both the how and why of starling murmuration, observers say that starlings often murmurate shortly before sunset when choosing a place to rest for the night and that there are no predators around.

A murmuration at sunset in the U.K.

A murmuration at sunset in the U.K. (Photo by James West on Flickr, Creative Commons license)

Andrew Chapman, writing from a semi-urban area near Washington, D.C., watches murmurations at two sites above high rise and mid-rise buildings that coincide with sunrise and sunset like clockwork, yet he’s never seen a predator. He hypothesizes that their murmurations could be predator-evasion practice.

A citizen science study of starling murmuration, conducted by four United Kingdom researchers, collated information from 3000 volunteers in 23 countries, including 70 from the United States. Their two-year study, each year running from October to March when starling murmuration is most common, gathered material on murmuration size and its duration in relation to the location, season, time of day, habitat, temperature and predator presence and behavior.

A murmuration at the RSPB Minsmere in the U.K.

A murmuration at the RSPB Minsmere in the U.K. (photo by Airwolfhound on Flickr, Creative Commons license)

The size of these flocks ranged as high as 750,000 birds but averaged 30,082 birds. The length of the murmuration was 26 minutes in the U.K., 18 minutes in other native starling countries, and 16 minutes in the U.S. and Canada, and was positively affected by day length and temperature.

Birds of prey were recorded at 29.6% of murmurations and the most common predators in Europe were sparrowhawks followed by buzzards, marsh harriers, hen harriers, and peregrine falcons. But in North America mostly peregrine falcons went after them, followed by red-tailed hawks, Cooper’s hawks, and, in the West, prairie falcons, according to Nick Dunlop, who has been photographing and studying murmuration in California’s Central Valley during migration for years.

A redtailed hawk hunting starlings

A red-tailed hawk hunting starlings (Photo by Jasper Nance on Flickr, Creative Commons license)

The citizen science study found that when a predator appeared, the birds went down together in a murmuration to roost rather than dispersing from the site as they did if there was no predator and thus concluded that starling murmurations were primarily an anti-predator adaptation. On the other hand, they noted that “the murmuration-predator relationship could…be as much (potentially more) driven by murmurations attracting predators—larger murmurations being more attractive—than by predators causing starlings to murmurate.”

So, despite all these studies, the question of why remains an enigma.

But European starling numbers have been falling across northern Europe and the U.K. since the 1980s even though they are thriving in North America. Thus far, ornithologists have not figured out why but have put them on the red list of concern in Europe.

Perhaps, our continent will become the last bastion of safety for these highly intelligent birds. Some researchers speculate about a “group mind” that regulates how flocks survive, especially during migration and fear that once numbers reach a certain low point, such as our passenger pigeons did, they are doomed to extinction.

In the meantime, I will revel in the opportunity to view these unique gatherings of starlings every autumn as they visit for a short time on our mountain, imagining how much more impressive those extinct passenger pigeon flights must have been.

Tom’s Finch

On the last day of September, our son Mark found the first migrating white-crowned and white-throated sparrows behind the barn and guesthouse. He also pointed out a Lincoln’s sparrow he had discovered at the edge of the hedgerow bordering First Field.

A Lincoln’s sparrow in Chester County, PA, on October 5, 2015

A Lincoln’s sparrow in Chester County, PA, on October 5, 2015 (Photo by Kelly Colgan Azar in Flickr, Creative Commons license)

I’m not an expert on the “little brown jobs,” as birders refer to the many look-alike sparrow species. While I’ve learned song, chipping, field, American tree, and white-throated sparrows because they are here for months either during the breeding or wintering seasons, I had never seen nor heard a Lincoln’s sparrow until Mark showed it to me.

At first I thought it was a song sparrow, and I wondered how many Lincoln’s I had dismissed over the years as song sparrows. They are both in the genus Melospiza, along with swamp sparrows, and the one Mark found even had the diagnostic dark breast spot of a song sparrow, although most Lincoln’s do not. But this sparrow was smaller than a song sparrow, had grayer head stripes, lighter streaking on its sides, a broad, buffy-colored chest band, and a white belly.

After that I looked more closely at the sparrows on First Field which was, at that time, a 37-acre goldenrod and aster meadow. On October 2 I was outside at 9:30 a.m. and, as I neared the field, birds flew up from the browning goldenrod including several Lincoln’s sparrows with a song sparrow.

Audubon’s painting of the Lincoln’s sparrow, the “Lincoln finch” as he called it

Audubon’s painting of the Lincoln’s sparrow, the “Lincoln finch” as he called it (Image in the Wikimedia, in the public domain)

Then began a burble of song at song sparrow pitch but with less structure. It was pure, bright bird music, described as warbling and wren-like by some observers. But when artist and naturalist John James Audubon first discovered it in Labrador in 1833, he wrote in his Ornithological Biography that “the sweet notes of this bird as they came thrilling on my sense, surpassing in vigour those of any American Finch with which I am acquainted, form[ed] a song which seemed a compound of those of the Canary and Wood-Lark of Europe.”

Audubon and his companions chased this new species from bush to bush, trying to shoot it for a type specimen until finally 19-year-old Maine native, Thomas Lincoln, “with his usual unerring aim,…cut short its career…I named it Tom’s finch, in honour of our friend Lincoln, who was a great favourite among us.”

The last time I saw Lincoln’s sparrows in First Field was the fifteenth of October when they still looked to me like song sparrows but sang their warbling song. According to The Birds of Pennsylvania by Gerald M. McWilliams and Daniel W. Brauning, most records for Lincoln’s sparrows here are from the first week in September to the fourth week in October, and banding records at Powdermill Nature Reserve record as many as 15 birds a day during the first and second weeks in October.

Lincoln’s sparrows breed from Alaska across Canada as far north as northern Quebec and Labrador in eastern Canada, south through the western mountain ranges in the United States, and from northern Minnesota to eastern Massachusetts. The closest known breeding range to Pennsylvania is in northern New York state, although there is one record of a singing Lincoln’s sparrow on July 24, 1988, at 2300 feet in elevation at Rickett’s Glen State Park in Luzerne County.

Lincoln’s sparrows east of the Mississippi River usually winter from northwestern South Carolina, Georgia and Alabama to central Florida. Those west of the Mississippi River can migrate sometimes as far south as Costa Rica and Panama, making them adventurous migrants that head farther south than most sparrows, but no matter where they go, they always use brushy, weedy areas close to shrubs both when they are migrating and on their wintering grounds.

They also migrate through Pennsylvania during the spring, usually in May, but they move through the commonwealth more quickly than during their dawdling fall migration, and as many as 30 have been counted at Presque Isle State Park near Erie.

In eastern North America, breeding Lincoln’s sparrows are birds of boreal shrub lands that are sometimes boggy. Because they are often bullied by song sparrows, according to J. Murray Speirs and Doris Huestis Speirs, who studied them from 1955 to 1957 near the north shore of Lake Superior in the Thunder Bay District of Canada, Lincoln’s sparrows could only breed in the same area as their congeners “by dint of persistent passive resistance: they always fled and returned later by stealth.”

The Speirs observed Lincoln’s sparrows on trout hatchery grounds from their car because “with black flies, ‘no-see-ums,’ and mosquitoes active and plentiful, a parked and closed car seemed the only livable observation point in the country.”

A Lincoln’s sparrow singing

A Lincoln’s sparrow singing (Photo by Gary Leavens in Flickr, Creative Commons license)

They and other researchers have found Lincoln’s sparrows difficult to study because of their skulking, secretive nature. Still, the Speirs had no trouble seeing the males singing from elevated perches, defending their acre of territory from other Lincoln’s sparrows by singing, buzzing calls and wing-flapping, and breeding by pouncing on their mates, usually after the females encouraged them. The Speirs’ pair was less secretive than most Lincoln’s sparrows where mating was concerned, copulating on the ground, on brush piles, on a picnic table, even on a sign, and one morning, while the female was nest-building, seven times between 8:00 and 10:13.

But the Speirs couldn’t find that nest even though they watched where the female landed, first with grass and later food in her bill. Finally, with another couple, they crawled around on their hands and knees and still couldn’t locate it. Then, after supper on June 24, 1956, Neil Atkinson, a young school boy, “came puffing into our house, having run the mile from the nest site, to announce that he had succeeded in locating the nest. Immediately, we went back with him, and there the nest was, right where we had looked, but set well down into the ground under a pile of last year’s brush cuttings. It looked like a little black hole.”

A Lincoln’s sparrow hiding in low shrubs in Ontario

A Lincoln’s sparrow hiding in low shrubs in Ontario (Photo by Yankech gary in Flickr, Creative Commons license)

They added that the Lincoln’s sparrows use “shrub growth less than 8 feet high for concealment and from which the male can sing, openings carpeted with grasses, heaths, or annuals less than 2 feet high in which they can forage, and a substratum of brush cuttings, grass clumps, or sphagnum that the nest may be sunk into.”

A female Lincoln’s sparrow digs out a small depression in the ground and using willow bark, grasses and dried sedges weaves a four inch by two inch nest, which she lines with a thick layer of thin, soft plant material. In it she lays three to five pale greenish to pinkish eggs specked and blotched with brown. She then incubates the eggs for 13 days.

The Speirs found it difficult to locate the nest because the female engages in what ornithologists refer to as the “rodent-run” when she leaves and returns to the nest after eating. Holding her wings against her body she lowers her head and breaks through a tunnel in the vegetation or later, during incubation, she flaps her wings and noisily breaks through vegetation especially if she is defending the nest from an intruder such as short-tailed weasels, shrews, or gray jays, all of which may prey on eggs or nestlings.

The male remains solicitous, mate-guarding her particularly during egg-laying because most studies on their breeding grounds have found twice to three times as many males as females so they are precious commodities.

A Lincoln’s sparrow in the John Heinz National Wildlife Refuge, Philadelphia

A Lincoln’s sparrow in the John Heinz National Wildlife Refuge, Philadelphia (Photo by Brian Henderson on October 5, 2015 in Flickr, Creative Commons license)

He also pitches in to feed them as soon as the helpless, altricial young emerge from their shells, although mostly the female broods their helpless hatchlings for a portion of their early nesting period at one to five days of age. The Speirs’ sparrows were fed green caterpillars, small white moths, and young grasshoppers, but overall, adult Lincoln’s sparrows over a year consume both insects and small seeds in equal amounts.

The young Lincoln’s sparrows mature quickly and leave their nest at 10 to 11 days old, although they can’t fly yet and spend most of their time hiding under dense shrub cover, but they often sleep at night back in their nest for several days. They practice flying during the day by first hopping and wing-flapping to nearby branches, then gradually making short and then longer flights until they are able to fly well by 18 days of age.

Because Lincoln’s sparrows are difficult to observe on their boreal breeding grounds due to their secretive natures, much of their biology and ecology are still unknown. Yet their numbers seem high during migration so they are in no danger of disappearing.

I look forward to seeing and hearing their singing this fall now that I know they visit our First Field. (See a YouTube video below that shows a singing Lincoln’s sparrow.) To me they are examples of the wonder of the natural world where I can always find something new even on familiar ground.

Audubon’s Pewee

It’s a day in late May and already the nests of our eastern phoebes are bursting with nestlings preparing to fledge. Over the 47 years we have lived on our mountain, our buildings have hosted many eastern phoebe nests.

A phoebe in Plummer’s Hollow

A phoebe in Plummer’s Hollow (Photo by Dave Bonta in Flickr)

Some buildings, such as the guesthouse portico and the old outhouse, contained nests for several decades, but the outhouse finally collapsed and the phoebes deserted the guesthouse portico after years of successful fledgings. They continue to use either the outside or inside of the small springhouse, while the barn overhang has become a more recent popular nesting place.

Still, there has never been a year when phoebes have not used the top of a veranda column and one of the garage beams to raise families, even though we tried to discourage the veranda column nest sites when we had it repaired and painted by blocking in the flattened tops of the columns. Undeterred, phoebes molded their nests around the obstructions.

Eastern phoebes have been building their nests on human homes and outbuildings for centuries and were known in the 19th century as “barn pewees” as well as “bridge pewees” because they also favor the undersides of bridges. Before the advent of human dwellings and even today, they will build nests in natural rock outcroppings. All such choices protect their nestlings from the weather and often predators as well.

The Eastern phoebe (Sayornis phoebe)

The Eastern phoebe (Sayornis phoebe) (Photo by Soerfm in Wikimedia, Creative Commons license)

Members of the Tyrant Flycatcher family, eastern phoebes follow the first flush of insects north from their winter homes in the southern United States, Texas, and Mexico, often arriving in Pennsylvania in early March and leaving in late October. Sometimes they must survive late spring snow storms and are able to subsist on small fruits instead of insects until the weather improves.

These gray-brown birds with off-white throats and bellies are the first songbirds to arrive on our mountain around March 15. When I hear the raspy “fee-bee” of a male phoebe and see this tail-flicking flycatcher on a wire near the barn catching insects from the sunny side of the building, I know that spring is here.

In scientific circles, eastern phoebes are known as “suboscine” birds because their songs are innate instead of learned like those of “oscine” birds such as wood thrushes. But lately bioacoustic studies of their songs detected variations among male song characteristics that are not obvious to our ears but are to those of the birds.

John James Audubon’s house at Mill Grove

John James Audubon’s house at Mill Grove (Photo by Dennis on Flickr, Creative Commons license)

Eastern phoebes should be credited with first arousing bird artist John James Audubon’s interest in birds. When he was a youth, he lived at Mill Grove on the Perkiomen Creek in Chester County. Early in the spring of 1804, he found the empty nest of the bird he called “Pewee” or “Pewit flycatchier,” fastened to a rock in a cave on his property.

When the cave phoebes returned, he spent many hours watching them as they went about their phoebe business. “Before a week had elapsed,” he wrote in his Ornithological Biography, “the Pewees and myself were quite on terms of intimacy.”

Beginning on the tenth of April, he watched them repair their old nest as “they brought fresh materials, lined the nest anew, and made it warm by adding a few soft feathers of the Common Goose which were strewn along the edge of the creek water.”

Four eastern phoebe chicks in their nest

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

Even today, eastern phoebes often refurbish old nests instead of building new ones, since building a new nest takes five to 14 days and refurbishing an old one four days or less. One recent study found that new nest builders finished their first clutches later, were less likely to raise a second family, and lost their nesting attempts more often because of fallen nest structures, all of which led to “lower seasonal reproductive effort,” the scientists concluded.

Audubon’s close observations of phoebes’ family life reminded me of the time I spent watching a guesthouse portico family back in the early 1980s. The female refurbished an old nest and she then laid five white eggs.

The Guest House portico where I watched a phoebe nest; the arrow points to the location of a bat which also chose to nest under the roof another time

The Guest House portico where I watched a phoebe nest; the arrow points to the location of a bat which also chose to hide under the roof another time (Photo by Dave Bonta on Flickr

I sat inside the front door of the guesthouse and watched the family through the portico window, but I also climbed up on a chair outside and held a mirror above the nest to check the eggs. The female is the sole incubator, even sleeping in the nest overnight. It takes 16 days until the eggs hatch, and most eggs in a single nest, including the ones I watched, hatch within 24 hours.

Audubon’s eggs hatched on the thirteenth day and in his nest of six eggs one did not hatch just as in the nest of five that I watched one never hatched. In both cases a parent removed the egg. Audubon opened the rejected egg and “found the embryo of a bird partly dried up, with its vertebrae attached to the shell…”

Since the hatchlings are helpless, almost naked, and in need of nearly constant brooding, I waited until they were 11 days old, fully feathered, and active before spending an hour every day watching the nest and recording the number of feedings. For four days they averaged 25 feedings, but when they reached 16 days of age, the feedings diminished to 15 an hour. A recent study showed that parents adjust their feeding rates according to the begging rates of their nestlings.

By then the nestlings were flexing their wings or standing on the edge of the nest and beating them. When they were 17 days old, the female parent appeared with nesting materials in her beak and, despite screams of hunger from the nestlings, proceeded to build a second nest beside the first one, yanking nesting materials from the side and top of the first nest as the youngsters watched.

While she worked on construction, the male fed the nestlings. But sometimes when they begged, she tried to push construction materials down their throats which they promptly spat out. They even jumped back and forth between the old and new nests but settled into the old nest by nightfall. The following morning, at 9:30 a.m., they all fledged at once. Usually though phoebes fledge one at a time over an hour or so as the veranda column nestlings do.

Audubon’s painting of the eastern phoebe, the “pewit flycatcher” as he called it

Audubon’s painting of the eastern phoebe, the “pewit flycatcher” as he called it (Image in the Wikimedia, in the public domain)

While I kept a “hands off” approach to the young, Audubon spent his time gaining the trust of both parents and nestlings so that they tolerated the light silver thread he fastened to the leg of each nestling before they fledged. This was the first time that birds had been banded in North America.

His banding proved the following year that phoebes return to their same nesting site and even nest, writing, “When the Pewees returned to Pennsylvania I had the satisfaction of observing them again, in and about the cave. There again in the very same nest two broods were raised…Several of these birds which I caught on the nest had the little banding ring on the leg…”

He assumed many of the pairs he observed, not only in the cave, but on farm buildings and his mill nearby remained faithful during one breeding season and from year to year. Recently, two studies found that most pairs were both socially and genetically monogamous within a breeding season. In one case in Indiana only 15 of 87 families had extra-pair young in at least one brood, most commonly the second brood.

Those researchers followed up with a second study in which they captured and color-banded 198 males and 237 females, studied them for three seasons, and discovered that they were faithful to their territories, nest sites, and mates within and between years with 85.5% of males and 92% of females mating with the same mate during multiple breeding attempts. But mates were replaced following their disappearance and probable deaths.

A study of infanticide in Kentucky by an unrelated male phoebe even while the female continued feeding her nestlings, resulted in the death of all the nestlings. The researchers hypothesized that the male parent of the nestlings had died or disappeared and that it was a way for a non-breeding male to obtain a mate and start his own family.

A phoebe nest with a brown-headed cowbird egg

A phoebe nest with a brown-headed cowbird egg (Photo by Galawebdesign in Wikimedia, Creative Commons license)

A greater threat to breeding phoebes has been repeated brood parasitism by brown-headed cowbirds. I’ve occasionally observed cowbird parasitism in our nests over the years, but never in the veranda column nests. A study of cowbird parasitism in New York State concluded that even over generations of birds, cowbirds prefer particular eastern phoebe sites, such as our old outhouse.

Other threats to phoebe eggs and nestlings are black rat snakes, raccoons, coyotes, blue jays, American crows, chipmunks, and house wrens, but not one of those predators has climbed or flown into the veranda column nests.

Overall, phoebes are incredibly successful throughout their range including Pennsylvania where they live everywhere except for the urban cores of Philadelphia and Pittsburgh. Although our songbird population has dwindled since the 1970s, it is comforting to know that eastern phoebes continue to thrive and are able to quickly adapt manmade structures for their own purposes.