Winter Visitor

Near the end of January I swept our back porch clean of an inch of snow before spreading bird seed. Immediately a sparrow throng of dark-eyed juncos, white-throated, song, and American tree sparrows mobbed the porch.

A group of chipping sparrows on a feeder

A group of chipping sparrows on a feeder (Photo by Anne Davis 773 on Flickr, Creative Commons license)

But one sparrow looked different from the rest and fed off by itself. Still, with its rusty-red cap it most resembled the four American tree sparrows, but it lacked a tree sparrow’s dot on its breast, gray eyebrow line and gray throat and neck. Instead, the mystery bird had a whitish eyebrow line and white throat and I thought it was a male chipping sparrow.

American tree sparrows are nicknamed “winter chippies,” because of their resemblance to chipping sparrows, but the tree sparrows at our feeding area continually chased off the chipping sparrow, since that is what it seemed to be. They seemed to have no problem figuring out that their almost look-alike was not part of their tribe.

The chipping sparrow on our back porch

The chipping sparrow on our back porch (Photo by Bruce Bonta, January 30, 2018)

I, on the other hand, wanted to make certain of my identification and insisted that my husband Bruce take a photograph of the chipping sparrow to send to our birding son Mark. He, in turn, posted it to the Pennsylvania eBird list, and everyone agreed that it was a male chipping sparrow.

I was pleased that he appeared on a Project FeederWatch day because I had never recorded a wintering chipping sparrow on our central Pennsylvania mountaintop, although they are regular breeders here in spring and summer. According to The Birds of Pennsylvania by Gerald M. McWilliams and Daniel W. Brauning, chipping sparrows are irregular winter visitors or residents where there is suitable cover near bird-feeding stations, but they are “usually found only during mild winters with little snow cover.” In addition, it is rare to find any chipping sparrows here beyond the third or fourth week in January.

But it had been bitterly cold and windy throughout January and the temperature as low as two degrees Fahrenheit below zero. We also had had frequent snow cover. Nonetheless, the chipping sparrow had evidently found shelter in the tall remnants of dried grasses and wildflowers below our porch steps at least for that day. Whether he found enough shelter and sustenance in our 37-acre meadow throughout the mild February or in the farm valley below, I didn’t see another chipping sparrow here until their usual spring appearance in early May.

The chipping sparrow—Spizella passerina—which is Latin for “sparrow-like finch,” was more aptly named by the “Father of American Ornithology” Alexander Wilson in 1810—Fringilla socialis—meaning “social sparrow” because even then chipping sparrows lived near human habitation. Then it was most likely rural homes, farmyards, pastures or orchards. Today chipping sparrows are also found in the suburban residential landscape of parks, gardens, golf courses, open woodlands, and woodland edges along roads and utility lines.

The fourth most widespread breeding bird species in Pennsylvania, the chipping sparrow is only behind the song sparrow, American crow, and American robin in abundance. Even during the days of John James Audubon back in 1841 he wrote about the chipping sparrow that “few birds are more common throughout the United States than this gentle and harmless little bunting.”

A chipping sparrow in Codorus State Park, Hanover, PA

A chipping sparrow in Codorus State Park, Hanover, PA (Photo by Henry T. McLin on Flickr, Creative Commons license)

Breeding across Canada to Alaska and throughout most of the United States, chipping sparrow migrants return to Pennsylvania from Central America, Mexico and the Gulf coast of the United States as early as the second week in March although the peak migration here is the last week in April or first week in May. I usually hear the male’s dry, monotone trill before I see him because he maintains his acre of territory mainly through song, but he also uses threat displays, chases, and even fights.

Once he establishes his territory, he courts a female by singing and short chases and they pair up a day or two after she arrives, usually about two weeks after the male does. She solicits copulation by crouching, her head and tail raised and vibrating. They mate several times in succession either on the ground or in elevated places such as fences, tree branches, and telephone lines.

Here on our farm the electric wires are favorite places, and we tend to think of chipping sparrows as exhibitionists. Both sexes engage in what ornithologists call “extra-pair copulations,” and once females are on their nests, scientists have found that some color-banded males copulate with other females on neighboring territories.

A chipping sparrow with nest material

A chipping sparrow with nest material (Photo by Gary Leavens on Flickr, Creative Commons license)

During nest-building and egg-laying by a female, though, the male keeps close as if he is guarding her. She seems to choose the final nesting site in a wide variety of trees and shrubs, but conifers are preferred over deciduous trees. However, crabapple trees are favored next, followed by honeysuckle, various maples, ornamental trees and shrubs, hawthorn, currant and even vines such as English ivy. Wherever she builds her nest, usually it is hidden in foliage three to 30 feet from the ground.

Like most bird species, though, some chipping sparrows don’t follow the nest-building program. For instance, back in 1911, R.F. Miller reported that a chipping sparrow, three years in a row, nested in pepper plants hung up to dry in late summer in a shed on a Philadelphia County farm. Another nest, in Huntingdon County in 1923, was built in the bottom of a hairy woodpecker roosting cavity 10 feet from the ground. And Maurice Broun, the first caretaker at Hawk Mountain Sanctuary, wrote about a chipping sparrow nest 30 feet up in a maple tree overgrown with grapevines and another 50 feet on top of an oak tree.

The cup nest itself is built in four days by the female and is so flimsy you can often see through the rootlets and dried grasses she weaves and then lines with the hair of deer, raccoons, cattle, and humans, and has even been known to yank out hair from horses, her preferred nest-lining material.

She then lays two to seven pale blue to white, lightly streaked or spotted eggs and incubates them for 10 to 15 days. The male feeds her frequently while she is on the nest because she rarely leaves it especially near the end of the incubation period.

The nestlings emerge over a 24-hour period, and the parents immediately eat the eggshells. The male begins feeding their young within an hour of hatching while the female continues to brood her naked nestlings until they develop feathers. She gradually decreases brooding after their fourth day and joins the male in feeding them mostly weed seeds, followed by insects as the nestlings mature.

Eggs and nestlings are preyed upon by black rat, eastern milk, and eastern garter snakes, American crows, blue jays, and domestic cats while adults and flying youngsters are victims of Cooper’s hawks, American kestrels, red squirrels, and domestic cats.

Their nests are sometimes parasitized by brown-headed cowbirds, but often chipping sparrows alarm-call and use threatening displays to deter them and frequently desert nests with cowbird eggs in them. If a cowbird does hatch with chipping sparrow nestlings, both appear to survive.

A parent chipping sparrow feeding an immature bird

A parent chipping sparrow feeding an immature bird (Photo by Indiana Ivy Nature Photographer on Flickr, Creative Commons license)

After a nestling period of nine to 12 days, the young climb to the rim of the nest and then into tree branches and practice short flights. Their parents continue to care for them for three weeks or so, but the male does most of the care if the female is starting a second brood. Then the young gather in flocks of five to 15 birds to forage in weedy places.

Once their last brood is on their own, the adults leave their territory, and parents and offspring join foraging flocks of their own species as well as song and field sparrows, feeding in weedy fields, along fence rows and forest edges. Fall flocks range from 25 to as many as 1000 birds as they move in stages south for the winter along the coast and mountaintops, leaving Pennsylvania as early as mid-September and as late as the third week or later in October depending on the weather.

Because chipping sparrows occupy a wide variety of habitats during breeding and on their wintering grounds, they remain incredibly common birds with an estimated three million breeding males in Pennsylvania alone. So it looks as if we can look forward every spring to the return of these human-adapted birds.

 

The Art and Science of Feeding Birds

I first began feeding winter birds in November 1968 when we lived in rural central Maine for five years. At the beginning of November, I hung a feeder filled with sunflower and mixed seeds from the yard American elm tree, but it wasn’t until a wet, snowy November 10 that the first birds appeared. I glanced out a window of our cape-style farmhouse to see 11 evening grosbeaks in the feeder and on the ground beneath. After that, the grosbeaks appeared during snowstorms throughout late fall, winter and early spring.

Evening grosbeaks on a bird feeder

Evening grosbeaks on a bird feeder (Photo by Linda on the bridge to NewWhere on Flickr, Creative Commons license)

The following winter the grosbeak flock numbered as many as 100 on snowy days. They were joined by common redpolls, American tree sparrows, blue jays, white-breasted and red-breasted nuthatches, black-capped chickadees, hairy and downy woodpeckers, and a few slate-colored juncos. Even then, I was listing numbers and species and watching and recording their antics in and around the feeders.

When we moved to Pennsylvania in late summer of 1971, I hung our feeder from the top of our back porch, five feet from the kitchen door, and spread seed on the back steps and cement pad beneath. Back in Maine our active bird feeder had provided entertainment for the whole family especially our three young sons. And I was eager to see what species would visit our new home.

Evening grosbeaks made occasional visits, but there were only a few of them at any time, and before the end of the century there were none. Then, as now, white-breasted nuthatches are the first birds to spot me putting up the feeder every November. Common redpolls are uncommon visitors once or twice every other year. Blue jays, too, are intermittent visitors, having cached acorns for the winter, unlike in Maine where oak trees were scarce and we hosted 14 blue jays at a time. American tree sparrows are almost as numerous here as they were in Maine even though Maine is closer to their boreal breeding grounds. Slate-colored juncos, lumped together with several other junco species in 1983 and re-named dark-eyed juncos, are more numerous in Pennsylvania.

Hand feeding a black-capped chickadee

Hand feeding a black-capped chickadee (Photo by Yvon Hache on Flickr, Creative Commons license)

Hairy and downy woodpeckers rarely visit our feeders here because they have a large forest of deciduous trees they forage on. But in Maine we lived in the country surrounded by fallow fields that attracted bobolinks and eastern meadowlarks in the spring. Beyond the fields was a patch of mature white pines along a lake that hosted dozens of small vacation cabins, so there were less trees to furnish insects for woodpeckers.

We had black-capped chickadees in both places, and I learned to handfeed them here where it isn’t too cold to stand outside next to an empty feeder, my palm outstretched and filled with sunflower seeds. Usually, they landed on my hand within 20 minutes. It took the tufted titmice, watching the chickadees, a little longer to venture near.

Tufted titmice and northern cardinals weren’t residents in central Maine in the 1960s as they are now, so I was pleasantly surprised when they appeared at our Pennsylvania feeder. And not so pleasantly surprised when gray squirrels raided it. In Maine, gray squirrels rarely appeared and the more common red squirrels stayed in the pine forest. After struggling to keep the squirrels from our open, wooden feeder in Pennsylvania, I replaced it with a couple tube feeders, which they have not had much success invading.

A red-bellied woodpecker at a feeder in Pennsylvania

A red-bellied woodpecker at a feeder in Pennsylvania (Photo by Rona Proudfoot on Flickr, Creative Commons license)

In Pennsylvania the first red-bellied woodpeckers, previously a southern species, arrived in our yard in 1980, and after a few years became the most common of our feeder woodpecker species. In 1986 Carolina wrens, another southern species, visited the feeder area, although several times their numbers were reduced after severe winters. Lately, though, our warmer winters have kept them alive and thriving.

Once Project FeederWatch was launched in 1987 by the Cornell Lab of Ornithology, I started paying even more attention to feeder birds, devoting portions of two consecutive days each week to counting numbers and species.

Writing in Living Bird, the magazine of the Cornell Lab, Gustave Axelson summed up some of the results of Project FeederWatch studies. Common red polls used to irrupt south from their boreal breeding grounds every other year when aspen and birch seed crops were lower, but beginning in 2005, some FeederWatch counts in low redpoll years have been higher than expected and may mean that food in the boreal forest is scarcer.

A cooper’s hawk with its catch near a bird feeder

A cooper’s hawk with its catch near a bird feeder (Photo by Tony Alter on Flickr, Creative Commons license)

Cooper’s hawks are not migrating to Mexico as much as they used to. Many hang out near feeders, as many bird feeder watchers can attest to, probably because they have learned that feeders attract large numbers of prey such as dark-eyed juncos and American goldfinches, but their predation has not affected the overall numbers of these common species.

Northern cardinals have expanded their range and are now reliable feeder birds as far north as Quebec, New Brunswick and Nova Scotia not only because of bird feeders but because more people are landscaping their yards with shrubbery that provides cardinals with more food and cover.

Biologist Bernd Heinrich, writing in Natural History, recounted his studies on how birds managed to recognize and then use a food as foreign to them as cultivated sunflower seeds. First he watched as white-breasted nuthatches and black-capped chickadees often picked up seeds and then threw them aside. Heinrich opened those seeds and found them empty of a nut. He hypothesized that the birds were testing the weight of every seed, knowing that if it was too light, it was useless as food.

A black-capped chickadee opening a seed

A black-capped chickadee opening a seed (Photo by Christa R. on Flickr, Creative Commons license)

Heinrich also began to observe how each species ate oil sunflower seeds because their bills weren’t designed to handle this unnatural food. It took a chickadee 35 seconds to grab a seed, fly always to the same nearby maple tree, perch on a slender branch on which it could curl its toes around and over the seed, hammer it open with its bill, extract and eat the seed and fly back to the feeder for its next seed, actions that I and other bird feeder watchers have observed. But Heinrich thought to time it and to further add that, “broadly speaking, the branch constitutes tool-use.”

Blue jays do the same as chickadees, although they need a larger branch for their larger feet. They too use the same branch over and over, but unlike chickadees that don’t cache their seeds, a blue jay will sometimes fill its buccal pouch with seeds and fly off to cache them.

Nuthatches and woodpeckers take the seeds, one at a time, fly with it to a favorite cleft in tree bark, shove it in the cleft, break it open with their beak, and eat the nut.

Wild turkeys at a feeder in Pennsylvania

Wild turkeys at a feeder in Pennsylvania (Photo by Aaron of NEPA on Flickr, Creative Commons license)

Heinrich also wondered about predation risk and hypothesized that, “if feeding efficiency is measured in terms of the least time needed to forage for the most food secured,” then mourning doves and wild turkeys are best at this. Heinrich’s doves come at first light and dusk for three minutes at a time and eat 90 seeds a minutes. They spend the rest of the day sheltered in a spruce/fir thicket digesting the seeds. Wild turkeys eat 135 seeds a minute. Both species have crops where they store their seeds. While resting, they move the seeds to their gizzards where they are ground up.

A Cornell Lab study tackled the question of how black-capped chickadees, tufted titmice, white-breasted nuthatches and house finches weighed the possibility of starving on a cold winter’s night to risking predation while eating birdseed to sustain themselves. They set up feeders near the Lab’s headquarters that contained radio frequency identification (RFID) technology. Then they captured and fitted the birds with little RFID tags which enabled those feeders to record every bird’s visit. In two winters they recorded 472,368 feeder visits by 94 tagged birds.

All four species began eating at the feeders a half hour before sunrise and visited more and more frequently as the day passed Their numbers peaked two hours before sunset and then declined sharply for all but the white-breasted nuthatches. They hypothesized that the birds are less concerned about day-flying predators—Cooper’s and sharp-shinned hawks—than they are nocturnal predators, primarily eastern screech-owls.

A tufted titmouse at one of our feeders

A tufted titmouse at one of our feeders (Photo by Eva Bonta and used with her permission)

Still another Lab study was on whether bird-feeding hurts or helps birds since more than 50 million North Americans feed one million tons of seed to birds every year. They studied 98 species of birds that use feeders the most and found that they do as well or better than those birds that don’t use feeders. Feeder species showing declines, such as evening grosbeaks, seemed to because of other pressures like habitat loss.

Conversely, those that needed the most help, such as seabirds, shorebirds, and tropical birds, are not feeder birds so we aren’t helping the neediest birds.

Still, no matter where we hang our feeders, we can feel a connection to the natural world that may inspire us to advocate for those many species that need our help.

 

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.