Little Brown Bats

little brown bat in a crack on the side of a house

The Guest House portico bat in 2007

Living, as we do, in an old country house, we often hear strange noises.

On an August evening, my husband Bruce and I sat in the living room reading. Shortly after 8:00 p.m., we heard unusual sounds coming from either the kitchen or sitting room.

We looked up at each other and then resumed reading. Both of us were engrossed in our books and didn’t feel like moving.

After all, many times we had investigated a noise and found nothing.

Then, there were more noises.

“I hope it’s not a bear,” I whispered to Bruce, remembering an attempted bear and cubs break-in back in June. “We’d better check it out.”

Because it was a wet night, it was already dark, and we couldn’t see a thing until Bruce switched on the sitting room lights. Then we ducked as a bat circled the room, narrowly missing the plates on our seven-foot-high plate rail.

Bruce opened the veranda door, but the bat continued its circling flight inside. As the minutes passed, I worried that mosquitoes, which had earlier driven us from the veranda, might get into the house.

But the bat was probably scooping up any that dared to enter and paid no attention to our feeble attempts to herd it out the door.

location of the bat in the previous photo

Location of the bat in the previous photo

Twice the bat barely missed the open door and once it landed for a few seconds on the wall, giving us a good look at its lustrous brown fur, but mostly it kept circling at plate rail height.

Bruce and I moved closer, he on one side of the door, I on the other, and I ducked reflexively every time the bat neared my head, even though I knew that its echolocation ability would keep it from hitting me.

Finally, it swooshed through the open door, and we breathed a sigh of relief. I was also elated that at least one little brown bat had escaped the white-nose syndrome (WNS), a fungus that has killed at least 95% of little brown bats throughout eastern North America since February 2006 when the disease was first discovered in a cave in Schoharie County, New York.

This cold-loving fungus Pseudogymnoascus destuctans only affects hibernating cave bats, which include the already Federally-Endangered Indiana bat, as well as the State-Threatened eastern small-footed bat, big brown bat, eastern long-eared bat, and tri-colored bat, but the little brown bat, also called little brown myotis, common bat, and cave bat, along with the eastern long-eared and tri-colored bats, is especially susceptible to the disease.

Dee Ann Reeder, A Bucknell University professor who has been studying bats in her bat vivarium even before the disease appeared, has been trying to understand how bats are affected and has been using little brown bats as her test subjects.

In a two-year captive study, she found WNS affected female little brown bats more than males and that bats kept in colder temperatures survived longer than those in warmer temperatures.

Little brown bats hibernating at Woodward Cave in central PA, February 2006

Little brown bats hibernating at Woodward Cave in central PA, February 2006

Reeder has worked closely with Greg Turner, PGC’s Endangered and Threatened Mammals Section Supervisor, to try to mitigate the disease, but this fuzzy white fungal growth around a bat’s muzzle, ears, and wing membranes thrives in winter hibernaculums—natural caves and old mines in Pennsylvania, such as the gated Hartman Limestone Mine at Canoe Creek State Park.

Back in 2008, when the PGC conducted its biannual count of bats at that mine, there were thousands of healthy, hibernating, mostly little brown bats. Three years later, they counted 38 total bats. And other hibernaculums throughout the state also contained few live bats.

Because bats cluster together in winter hibernaculums, the disease spreads easily from bat to bat. WNS causes them to rouse every few days instead of every few weeks as they used to do. The small size of little brown bats means they have less fat reserves to begin with so they quickly lose their fat reserves and starve.

They also lose more water through evaporation, and when they emerged, starved and dehydrated, for instance, from the Hartman Limestone Mine, they ate snow. In addition, little brown bats have suppressed immune systems during hibernation, which makes them more vulnerable to the fungus. Thus, once nicknamed the common bat, they are now rare.

Hibernating bats among the stalactites in Woodward Cave

Hibernating bats among the stalactites in Woodward Cave

Scientists say the best case scenario would be a full recovery of the bat population in 200 years! As of April 2015, the cave bats in 26 states and 5 Canadian provinces have been infected with WNS and still the disease rages westward at a frightening pace.

This is a huge wildlife disaster, certainly the worst in my lifetime, and all because some cavers, probably from Europe, where cave bats have evolved with the disease, brought the fungal spores over on their clothes.

Lately, there have been a few bright spots in this dismal picture. In 2014 the Hartman Limestone Mine cave bat count was 155, and this year 71 bats. Although the numbers are still low, according to Greg Turner, bats are coming into hibernation heavier, even the few juveniles, and they have fewer skin lesions on their wings. They also spread themselves out in hibernaculums. But all such changes may be due simply because there are few bats left to compete with for food and space.

Knowing all this, I welcomed our little brown bat visitor. One bat eats between 800,000 and 1 million insects a year including moths, wasps, gnats, midges, beetles, mayflies and especially mosquitoes, scooping up prey with its wings while flying or grabbing prey with its mouth.

Little brown bats have both day and night roosts during spring, summer and early fall. They like to roost near ponds, lakes, rivers or streams in buildings or trees, under rocks and woodpiles, and in caves. Females and their young occupy warm nursery roosts in natural hollows, buildings, such as old churches, at Canoe Creek State Park, for example, and attics.

A bat on the side of a concrete block

A bat on the side of a concrete block outside our barn, 2007

They sleep almost 20 hours in a 24 hour cycle, saving their energy for when insect prey is most abundant—from dusk to two to three hours later and again for a shorter period before dawn. Flying at between 13 and 22 miles an hour, they hunt their prey using echolocation, a process in which they orient themselves by emitting high-frequency sounds and then interpreting the reflected sound waves.

They mate in autumn before hibernation, but fertilization occurs after the females emerge from hibernation the following spring. After a gestation period of 50 to 60 days, a single pup is born to a female in late May or early June.

Born with their eyes closed, the young hang in the nursery roost while their mothers hunt for food. The rest of the time, for two weeks, they cling to their mother’s nipple until they are two weeks old. At three weeks of age they learn to fly, and a week later they are adult-sized—between 3.1 and 3.7 inches with a wingspan of 8.6 to 10.5 inches.

Female little brown bats are larger than males, but all adults need to eat half their body weight each night, and new mothers more than their body weight. One study in New Hampshire of pregnant and nursing mothers found that they ate 7 insects per minute.

Before WNS, we could sit out on our unscreened veranda even after dark and rarely see or hear a mosquito. A few male little brown bats roosted in our barn and in openings under our roof and the guesthouse portico roof. We often watched them flying over our field and imagined them scooping up water from our stream.

Close-up of the little brown bat in the previous photo

Close-up of the little brown bat in the previous photo

Now the mosquitoes force us inside every evening. Farmers, who may not have realized how many harmful insects bats eat, will be forced to use more pesticides.

Little brown bats have few predators, although occasionally a snake, raccoon, skunk, or cat may enter a hibernaculum and kill a few. They’ve also been caught on barbed wire fences or in burdock bristles.

Before WNS, humans wiped out entire cave or attic nursery populations, but bat education by dedicated people such as Cal Butchkoski, a wildlife biologist for the PGC who spent countless hours at Canoe Creek State Park and other venues, presenting excellent programs on bats, and Environmental Educator Heidi Mullendore at the park who organized several successful Bat Festivals there, had begun to change peoples’ minds about bats. The PGC had also gated many vulnerable winter hibernaculums throughout the commonwealth.

Now it is illegal to kill even one bat of any species. With 6 million gone, “every bat we find is precious and needs to be conserved,” Dee Ann Reeder says.

All photos by Dave Bonta.

Amazing Hooded Warblers

Hooded warbler singing by JanetandPhil

Hooded warbler singing (photo by JanetandPhil – CC licence)

It’s a hot, humid day in mid-July, and a hooded warbler sings his clear, whistled “ta-wit, ta-wit, ta-wit, tee-yo” song. Because hooded warblers have one of the loudest and clearest of warbler songs, it can be heard a long distance, which may be why I can hear it despite a slight hearing loss as I age.

But hooded warbler song is tricky. Individual males have their own version of songs, especially the first several syllables. I’ve learned to listen for the last “tee-yo,” which I hear as “wee-zu” to identify them. This works most times unless a male decides to sing another version that rises in pitch at the end and, to my ear, sounds totally different from his usual songs.

At least hooded warbler song is distinctive, unlike the “buzzy” songs of some warblers. Hooded warblers also have a distinctive look that they keep throughout the year. The black hood, for which they are named, encircles their bright yellow head like a monk’s cowl.

Even the females have a trace of that hood or, at the very least, a black spot between their bill and their eyes. Those eyes are unusually large and dark, larger than 32 other warbler species.

Their breasts and bellies are also bright yellow and their backs and tails yellow-olive. They frequently flick those tails showing white outer tail feathers, which is still another identifying characteristic.

Best of all, when many fall migrating warblers have exchanged their flashy spring and summer feathers for dull fall and winter ones, hooded warblers remain their black-cowled, yellow-bodied selves.

Hooded warbler female by Joby Joseph

Hooded warbler female (Joby Joseph – CC licence)

Seeing these warblers, though, is not easy because they are understory skulkers, often feeding on or near the ground. They also nest close to the ground in shrubs and saplings.

Called “forest dependent gap specialists” by Dr. Bridget Stutchbury, who has studied hooded warblers extensively at her Hemlock Hill Research Station in northwestern Pennsylvania, Stutchbury writes in The Second Atlas of Breeding Birds in Pennsylvania that singing hooded warblers are most abundant in deciduous forests and breed in tree-fall gaps where sunshine encourages thick undergrowth.

Unfortunately, hooded warblers are also attracted by logged fragmented forests, and so are brown-headed cowbirds. In one study, by Stutchbury’s student, Margaret Eng, over half the hooded warbler nests in fragmented forests had cowbird eggs, and, as Stutchbury writes in her excellent book, The Bird Detective, “nesting success was so low that their fatal attraction to partially logged areas was actually driving the population numbers down…”

Despite this, though, hooded warbler numbers in Pennsylvania have increased an amazing 71% between the first and second atlasing projects. This is partly due to the expansion of their core range in western Pennsylvania, especially the northwest, as well as in Pennsylvania’s Ridge and Valley Province.

Like several other bird species, such as Carolina wrens and northern cardinals, hooded warbles are a southern species moving steadily north into New York state and Ontario. Scientists are not certain why, but Stutchbury says that “maturation of forest, combined with a possible response to climate change, may be important factors.”

Hooded warbler nest by Richard Bonnett

Hooded warbler nest (Richard Bonnett – CC licence)

Certainly, here on our mountaintop Ridge and Valley Province home, I hear and see more hooded warblers than I used to. Last summer I heard them along Laurel Ridge Trail, beside the Far Field Road, and along Greenbrier and Ten Springs trails, all forest areas with a shrubby understory.

Hooded warblers return to our mountain from the last week in April to the first in May, and we count as many as seven during our participation in the Pennsylvania Migratory Bird Day count the second Saturday in May. The males arrive first and occupy the same territory they had the previous year by chasing off intruders.

Females settle on a territory and mate shortly after arrival, favoring males that sing four to seven songs per minute. Possibly this signals to a female that such males will be strong enough to feed their young the average thousand times they deliver food during the raising of one clutch of young hooded warblers. According to Stutchbury, hooded warblers that sing less are more likely to have unfaithful mates. In fact, one-third of female hooded warblers have offspring fathered by a neighboring male.

The females choose nest sites in shrubs or saplings seven to 63 inches from the ground, although 25 inches is the average. It takes females two to six days to choose a site and build an open cup nest woven of soft inner bark, grasses, and plant-down with an outer wrapping of dead leaves, some of which hang down and camouflage the nest.

In Pennsylvania, blackberry, beech, black cherry, and prickly gooseberry are favorite nesting plants, but maple leaf viburnum, white ash, black and blue cohoshes, sugar maple, wild rose, yellow birch, hawthorn and hemlock are also used. All are native trees and shrubs. However, the only hooded warbler nest I ever found was in a thicket of nonnative Japanese barberry off Greenbrier Trail.

Here in Pennsylvania, first nesting attempts range from May 10 to June 11, and the second nesting from June 21 to July 19. Last summer on July 20, a hooded warbler distraction-displayed as I passed a thick understory of barberry, multiflora rose and blackberry, and I assumed a second nest was hidden within those prickly shrubs.

Hooded warbler on nest by USFWS

Hooded warbler on nest (USFWS – public domain)

The females incubate an average of four white eggs spotted with brown that look very much like those of brown-headed cowbirds. In northwestern Pennsylvania 62% of hooded warblers nests were parasitized by cowbirds, Stutchbury reported, possibly because cowbirds are attracted by chipping calls female hooded warblers make as they construct their nests. Usually cowbirds lay one or two eggs in a nest and remove one or more hooded warbler eggs at dawn before female hooded warblers arrive to lay their egg for the day.

After 12 days, the young hatch, and both parents feed them spiders and insects, the usual fare of hooded warblers, although only the females brood them.

At eight to nine days of age, the young fledge and can fly two to three days later. The parents divide up the fledglings and continue feeding them until they are five to six weeks old. But usually males take over the entire brood of fledglings if the females start second broods.

The males sing from the time they arrive until they leave for their wintering grounds in Central America. I’ve heard a male singing here as late as September 24, although peak migration time in Pennsylvania is from the fourth week in August to the second week in September.

Hooded warblers defend territories on their wintering grounds, but males prefer mature forests and females scrub, secondary forests and disturbed habitat, which is the first documented example of habitat segregation.

Male and Female hooded warbler by Louis Agassiz Fuertes, 1917

Hooded Warbler by Louis Agassiz Fuertes, 1917

Our son, Mark, who has lived off and on in Honduras over the years, has seen many wintering hooded warblers in shrubby areas and says they are always with Wilson’s warblers, a boreal breeding species that resembles a female hooded warbler except for the black cap of the male Wilson’s warbler.

Back in spring of 2010, Stutchbury attached tiny geolocator tags on the backs of five male hooded warblers to find out where they spend their winters. These tags record light levels and location information every two minutes and are now being used to track numerous songbird species.

A year later two of the five tagged hooded warblers returned to their territories in northwestern Pennsylvania, and Stutchbury and her team caught them in mist nets and analyzed the data. One male had flown south to the Florida panhandle, across the Gulf of Mexico and spent the winter in Nicaragua. In spring, he flew up to Mexico’s Yucatan peninsula, across the Gulf of Mexico, and up the Mississippi River Valley back to his exact same territory—altogether a 4,200 mile round trip.

When males return to their same 1.2 to 1.8 acre-territories, they use their long-term memory to identify nearby territories by the distinctive songs of the neighboring males. This minimizes the struggle for territory as they countersing with their neighbors and await the arrival of the females.

In the words of Samuel F. Rathbun, who studied the hooded warbler in west-central New York state early in the last century, “it is essentially a carefree song, musical, and often spiced with a little jauntiness, which in many ways perfectly reflects the actions of the bird.”

Hooded warbler by Paul Hurtado

Hooded warbler (Paul Hurtado – CC licence)

Stony Garden

boulder field at Stony Garden

boulder field at Stony Garden

The request appeared in my junk mail from someone named Anna Mintz. She wanted to interview me about ringing boulder fields in Bucks County, most notably Ringing Rocks County Park, for a Russian television program. Somehow, she had discovered an article I had written about the park years ago.

I tried to discourage her, explaining that I was no expert on ringing boulder fields and that we lived four hours away from Bucks County and five from New York City where she was working. Undeterred, she rounded up a Ukrainian camera man and arrived at a parking area near our private access road in late February. My husband, Bruce, transported them and their equipment up our icy, north-facing hollow road.

Forewarned of their impending arrival, I reviewed my folder of pre-Internet information on ringing boulder fields. Their geological history began approximately 200 million years ago in the early Jurassic Age. Ancient Lake Lockatong had covered most of Bucks County and then had gradually filled with sediments that had hardened into shale. Molten rock within the earth was forced into the shale and hardened into a ledge of olivine diabase rock, sandwiched within the shale. But over the eons, the shale’s upper layer eroded and exposed the diabase. Subsequent severe freezing during the last Ice Age, when glaciers came close to but did not reach Bucks County, causing so-called periglacial conditions, broke the diabase into boulders.

another view of Stony Garden

another view of Stony Garden

Most boulder fields, such as the one at Hickory Run State Park, don’t ring, and researchers puzzled over why only the boulder fields in a thin line from northern Bucks County to nearby Montgomery County outside of Pottstown ring with melodious tones. Those tones inspired Dr. J.J. Ott, back in 1890, accompanied by a brass band, to play several musical selections at Ringing Rocks County Park. Current thinking is that they ring because of the density of the rocks and the high degree of internal stress that occurred when the molten rock came close to the earth’s surface and quickly cooled and solidified.

After cramming that information into my head I googled “ringing boulder fields” to see if there was any new information on them, and I discovered Ringing Rocks County Park was not the largest ringing boulder field in the East. That honor belongs to nearby Stony Garden on State Game Lands 157. According to a Wikipedia article, Stony Garden consists of “a series of disconnected boulder fields extending for almost half a mile,” making it much larger than the eight acre ringing boulder field at the park. It also mentioned a trail that leads into a portion of Stony Garden’s boulder field.

I was determined to explore this place and knowing that my younger brother, Gary, and sister-in-law Barb, who live in south Jersey, enjoy hiking in Bucks County, Bruce and I invited them to join us there last June 9. As it turned out, Gary had had a bad night due to illness, but he urged Barb to go.

Marcia and Barb at the edge of the boulder field

Marcia and Barb at the edge of the boulder field

It was an overcast day, threatening rain, when we met at nearby Nockamixon State Park for a picnic lunch. Afterwards, following a game lands map, we found the parking lot and Stony Garden Trail off Stony Garden Road. Although the trail is only a little less than half a mile long, it had its challenges. It was rocky and wet and we had to crawl over and under several fallen trees and cross a tributary of Haycock Creek. For those reasons, we were glad to be wearing sturdy hiking boots and carrying walking sticks.

It quickly became obvious why this place is called “Stony Garden.” I was reminded of a rock garden, so neatly did the wide variety of wildflowers, ferns and shrubs grow in the soil between the rocks, such as blooming partridgeberry and Indian cucumber-root, the leaves of spring-blooming jack-in-the-pulpit, wild ginger, bellwort, and mayapple and especially the fern rock polypody, which is common in rocky areas. Along the tributary, tall meadow-rue flowered. We found a few spicebushes, a nice maple leaf viburnum, and even a small American chestnut tree.

When we reached the boulder field, Barb and I didn’t feel sure-footed enough to venture out on the boulders so we stayed on its edges tapping on small rocks and making a little “music.” But Bruce climbed out on to the open boulders and made them ring, creating a range of tones by tapping them lightly with a hammer. He quickly found that the best sound came from thin rocks.

Gary and Patrick Myers at-Ringing Rocks County Park

Gary (r) and his son Patrick at Ringing Rocks County Park

Remembering my childhood, more than 60 years ago, I was sorry that Gary couldn’t make it. We had often visited Pottstown’s Ringing Hill Park near the home of my paternal grandparents, and he and my younger sister Linda had leaped fearlessly from rock to rock while I and my youngest brother, Hal, being less surefooted, stayed seated on a boulder at the edge. I knew he would have enjoyed seeing this awesome place and joining Bruce in the middle of the field.

But on our day at Stony Garden, while Bruce made the rocks ring, Barb and I listened to wood thrushes, red-eyed vireos, and ovenbirds singing in the forest of red and black oak, black birch, basswood, American beech and tulip trees surrounding the rocks. We also noticed small weathering potholes in some of the rocks and intense pitting in others, photos of which appear in the Wikipedia article.

Later, we learned that an even larger boulder field existed deep in the forest. Unfortunately, by the time we made our way back to the parking lot, we had no more time to explore the rest of SGL 157. And by then the threatening storm was spitting rain. But all of the game land’s 2000 acres on the northwest slope of Haycock Mountain, including the boulder fields, were obtained by the game commission back in 1920.

According to LMO John Papson, the boulder fields themselves make attractive homes for chipmunks and probably a selection of other rodents. Furthermore, the surrounding rocky terrain does not prevent the deer from using the area, and, in fact, we did see a few tracks in the wet areas. In addition, the game land supports a healthy population of black bears, bobcats, coyotes, red and gray foxes, gray squirrels, and raccoons as well as white-tailed deer. Although there are food plots and some timber cuts, for the most part the forest we saw around the ringing boulder field is typical of the rest of SGL 157.

Marcia, Gary and Barb

Marcia, Gary and Barb at Ricketts Glen State Park

Today people come from Philadelphia and nearby suburbs, Papson told me, to hunt and hike, and they find it difficult to believe that this island of a forested mountain has such a wide variety of wildlife, especially black bears and bobcats, but their presence and other wildlife have been captured on trail cams. Judging from the mature trees growing in the forest, providing ample food for wildlife, SGL 157 should be a great place to hunt. But during the summer, when hunting opportunities are limited, taking your family to climb and ring the rocks should provide precious memories for youngsters, just as it did for me and my three siblings.

In Memoriam: Gary Alan Myers (February 12, 1946-June 24, 2014). He loved to roam the hills and forests of Pennsylvania.

Blue Canaries

indigo bunting by Matt Stratmoen

indigo bunting — photo by Matt Stratmoen (CC licence)

On an early May morning, I step outside and hear a warble of clear, bright, musical notes. The indigo buntings have returned. Also known as “blue canaries” because of their color and song, I’ve never been able to describe indigo bunting song to others except to say that I know it when I hear it.

Other folks have had more success or perhaps a better ear. Arthur A. Allen, a prominent Cornell University ornithologist back in the 1930s, described it as “sweet, sweet, where, where, here, here, see it, see it,” and when I listen to its variable song on the Cornell Laboratory of Ornithology’s website (the Lab was the brainchild of Allen’s), his description seems apt. But the Lab website cuts Allen’s description down to eight words instead of ten—“what, what, where, where, see it, see it.”

indigo bunting resting on an outdoor table

indigo bunting resting on an outdoor table — photo by Dave Bonta

In fact, both descriptions are correct. That’s because a male indigo bunting has one complex song that combines 6 to 8 kinds of notes in different sequences. Furthermore, that choice of notes in his song is unique to what ornithologists call a “neighborhood” of indigo buntings, i.e. anywhere from 3 to 4 up to 22 males in adjacent territories that average 3 acres. And males living approximately a mile and a half apart have different songs which they develop from a repertoire of about 100 notes.

Unlike many songbirds, indigo buntings do not learn their songs from their fathers during their natal year. Instead, as first year males 80% of them match the song of neighboring males while 20% appear to learn their song somewhere else before settling on their own territory. Once they establish themselves, indigo bunting males sing 200 songs an hour at dawn, one song per minute the rest of the day, and they sing well into August.

The brilliant Prussian blue males with wings edged in black are often described as a piece of the sky come down to earth and like the sky, which only appears to be blue, their feathers merely refract and reflect blue light. The only pigment their feathers have is melanin. This gives them a brown-black color that is obvious if you hold a feather so that the light comes from behind instead of toward it as we usually see the bird. For this reason, male indigo buntings look more black than blue in poor light.

The females, who do most of the work of raising young ones, are mostly brown with lightly streaked breasts and are often mistaken for sparrows. Like the males, they have silver-gray conical bills, but while the males perch on the highest point in the shrubby, overgrown fields they favor, belting out their songs, the females stay hidden, sitting on open cup nests they have woven in shrubs or saplings.

Courtship is short, and females settle on a male’s territory a day or two after arriving. She chooses the nest site in fields or the edges of woods, railways or roadsides, in shrubs, such as blackberries, gray dogwoods, multiflora roses, and staghorn sumacs, in goldenrods and nettles, or in sapling trees such as black locust, aspen, elm, black birch or maple. Usually she builds the nest 1.5 to 3 feet above the ground but sometimes as much as 10 feet later in the season. Nest materials of soft leaves, grasses, stems and strips of bark are held together by weaving and by wrapping the nest in spider webs, and grasses and sometimes deer hair line the nest.

indigo bunting nest by Richard Bonnett

indigo bunting nest — photo by Richard Bonnett (licence)

Then she lays 1 to 4 white eggs on subsequent days and begins incubating them after the last egg is laid. It takes from 11 to 14 days, depending on the weather, for her eggs to hatch. Once her chicks arrive, she broods and feeds them small insects, spiders, and berries, as much as 54 times a day with breaks averaging 16 minutes for very young nestlings. The only time she gets a rest is after the young fledge as early as 8 days old if they are disturbed but up to 14 days in cool weather, although on average they fledge at 9 to 12 days of age. The male then pitches in to help feed the fledglings and completely takes over after a few days. In the meantime, she is busy constructing a new nest, laying and incubating the second batch of eggs.

Our overgrown, brushy, 37-acre First Field and smaller Far Field appear to be ideal indigo bunting habitats, and occasionally I discover a nest. Last July 7, while walking around the Far Field on Pennyroyal Trail, I startled a brown female that scolded and skittered off into the grass. I couldn’t persuade her to reappear, but almost immediately I discovered a nest containing three white eggs in a small black locust sapling.

Five days later I again took the Pennyroyal Trail and found the indigo bunting nest intact but empty as if some creature had tipped it slightly and removed the eggs. I suspected a raccoon to be the culprit especially after I learned that one was observed by researchers removing eggs from a nest without disturbing it, but other possible nest predators include red foxes, opossums, feral cats, blue jays and snakes.

Then, early in August, while picking blackberries in a patch in First Field, I heard what sounded like a rapid “tick-tick.” It turned out to be indigo bunting fledglings begging for food. I had an excellent look at one perched in the deepest part of the patch, well-protected from predators. Once I glimpsed the female trying to fly in to feed them, but she veered off when she saw me, not wanting to give away the location of her fledglings. The fledgling I saw did flutter off to another part of the patch so it was able to fly a short distance. Last January I found their intact nest 3 feet from the ground in a black birch sapling at the edge of the blackberry patch.

indigo bunting female by Henry T. McLin

indigo bunting female — photo by Henry T. McLin (licence)

Here in Pennsylvania indigo buntings breed from May 6 until September 11 and they have nests with eggs from May 24 until July 9. But sometimes they have clutches as late as August 3, so the nest I found at the Far Field was a late, unsuccessful clutch. Early in the season, indigo bunting nests can be heavily parasitized by brown-headed cowbirds, however, in a Michigan study, 69% of nests were successful.

Because they are generalists that adapt to a wide variety of habitats, especially interspersed woodlands and farmlands, they are one of Pennsylvania’s most common songbirds with the highest numbers in our Ridge and Valley Province. They were abundant during both atlasing projects, and male numbers are estimated at 1.5 million. Still, the Breeding Bird Survey recorded a modest 15% decrease, perhaps because of conditions on their wintering grounds.

They begin leaving Pennsylvania late in August, but peak migration occurs during the last two weeks in September. During the second and third weeks in October, 50 or more birds have been observed in overgrown, brushy fields. They spend their winters in southern Florida, Mexico, Central America, and on Caribbean islands.

indigo bunting in the rain

indigo bunting in the rain — photo by Dave Bonta

But how do they find their way? It turns out that as young birds they are stargazers. And it was Cornell Lab ornithologist Stephen T. Emlen who proved this. Using what later was called an “Emlen funnel,” he put an indigo bunting experiencing migratory restlessness or zugenruhe into a funnel-shaped cage that he had line with paper, and supplied with an ink pad perch at its bottom. The bird repeatedly leaped from the ink pad to the funnel’s side, leaving its footprints on the papered wall. In that way, the bird left a record of its migratory direction and depending on its hormonal condition, oriented north or south. Emlen followed this by proving that those songbirds that travel at night use the stars as a guide, specifically the North Star, Polaris, which stays in the same position all night and the Big Dipper and other nearby stars which rotate around Polaris in a counterclockwise direction. In addition, Emlen found that they learned their way as young birds watching the sky at night. Since his work, other discoveries about bird migration continue to be made and they appear to use magnetic fields to orient themselves too.

Indigo buntings breed from the Great Plains eastward to the Atlantic seaboard and from southern Canada to the southern United States. Then they head to their winter homes. Many indigo buntings return to the same site both in their wintering grounds and their breeding grounds, according to a variety of studies, although the males seem to be more faithful to their home grounds than females are. It’s intriguing to realize that those males I see every year sitting on the same singing perches may be as wedded to our habitat as I am.