The Many-Tongued Mimic

Posted on November 1, 2021 by Marcia Bonta | 2 Comments

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

Every winter we have at least one unusual bird visitor. The winter before last it was the northern shrike. Last winter, during the pandemic, most birders were excited about the superflight south of boreal birds and welcomed huge numbers of pine siskins, red-breasted nuthatches and common redpolls, as well as evening grosbeaks and even hoary redpolls at their feeders. We saw only an occasional pine siskin with a flock of American goldfinches.

Instead, we were surprised by the appearance of a northern mockingbird on November 10 during a long period of Indian summer weather.

While northern mockingbirds are common yard birds in much of Pennsylvania, we had, up until 2020, only five detections of these birds on our mountain, and they had been in the spring. But our son, Mark, who was living in our guesthouse with his wife Paola and his brother, Dave, at the time, described the November mocker as a skulker that would appear around six in the morning and move quickly from its shelter in the huge old barberry hedge that stretches several hundred feet from the guesthouse to the shed, up to a lilac shrub near our veranda and then on to large forsythia bushes near our garage.

Mark continued to see the mocker every morning, but I didn’t have my first sighting until a cold day late in November as I headed across First Field. In the middle of the field, perched in a large, native, black haw shrub with four American tree sparrows, was the northern mockingbird. I had a good, long look at her mostly gray body with whitish breast and belly, white wing bars, and, when she finally flew, a flash of black and white tail feathers.

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

I decided she was a female because she never sang but merely “chipped” a few times at dawn. Female mockingbirds sing quietly only during nesting time, but males sing most of the year. Furthermore, according to K.C. Derrickson, who studied mockingbirds in southeastern Pennsylvania and Maryland, many females in Pennsylvania establish their own winter territories in November apart from their mates, based on the available fruit, cultivated or wild, in an area, especially multiflora rosehips. Although we had a few of the latter around the perimeter of First Field, we had a lot more barberry, mile-a-minute and even an old apple tree with apples still clinging to it.

My husband, Bruce, had the next sighting on a bitter cold afternoon in early December when she landed briefly on a hackberry tree outside the sunroom. Three days later, on December 10, I saw her again, this time alone, in the black haw shrub. She sat still as I crept closer and closer. Then she spread her black and white tail before flying across the field toward the barberry shrubs at the edge of Margaret’s Woods.

Northern mockingbirds prefer early successional habitat at low elevation (less than 1,300 feet), and Mark established that they had territories at the base of our mountain on the Sinking Valley side. This rural area with brushy pasture and agricultural fields bordered by dense shrubs along with the mowed lawns and shrubs of suburban homes is ideal mocker habitat, and we thought that “our” mocker had followed the powerline right-of-way that crosses the valley up to our property.

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

She made her appearance again during our Christmas Bird Count on December 20, and Dave saw her on a tree branch near his front porch on December 27.

Dave has had a Twitter account and blog for over a decade that he calls The Morning Porch, where he recorded her sitting in a bush beside our stream and chasing off other birds that tried to drink there on January 5. Mockingbirds are known to be aggressive toward their own species and other bird species too throughout the year.

The following day Bruce saw her land on our large bird feeder hanging on our back porch, but mockers are not usually feeder birds unless there is fruit or suet in feeder areas, neither of which we had.

On January 8 I had my best and, as it turned out, my last view of her. I had followed a deer trail through the dried goldenrod of First Field to the back of the barberry hedge. I pished and out from its depths popped the mockingbird. She sat on a hedge branch for a minute or so and then flew to the old apple tree below the hedge, where she poked at a few wizened apples and ate a little before flying away.

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

Dave had three more reports on his Morning Porch. The first was on January 12 when a mixed flock of winter birds flitted through the yard and the mockingbird flew over the guesthouse and peacefully joined them at a half-frozen seep.

On January 22 he wrote, “Half an hour before sunrise, the first inquisitive ‘chirps,’ mockingbird,” and finally on January 27, “Is it night or day? The 7 o’clock factory whistle [in our town] has the answer. Two minutes later the mockingbird begins to chirp—that take-charge tone.”

We can only hope she returned to the valley because after that came days of snow and cold that blanketed our mountain with more than a foot of snow and ice that lasted throughout February.

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

A member of the Mimidae family, the Latin name of the northern mockingbird is Mimus polyglottos roughly translated as “many-tongued mimic.” Mockingbirds, as a whole, don’t only mimic the sounds and calls of at least 200 songbirds but also a wide variety of natural and human-made sounds. For instance, one mockingbird at Boston’s Arnold Arboretum mimicked 39 birdsongs, 50 bird calls, and a frog and cricket, and the average number of song types of four males in southeastern Pennsylvania was 148 in 1980 and 167 in 1981.

Mockingbirds sing all day and sometimes all night especially if they are unmated males, beginning in February through most of November. Mockers also may have a different slate of songs for fall and spring and are known as open-ended learners, like parrots and European starlings, meaning that they continue to learn new songs throughout their lives. They sit and sing on top of shrubs, fences, trees, utility lines and poles and walk, hop, or run on the ground with their tails cocked up. The male’s singing is thought to be both a way to attract and stimulate his mate and to defend his territory from other male mockingbirds.

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

Males will fight over territory boundaries by first flying toward each other, landing near the boundary and silently hopping from one side to another. When this approach doesn’t work, they may fly at each other and grab with their wings and claws and peck. While males keep off males, females keep away other females.

Northern mockingbirds are mostly monogamous and some pairs stay together for life. In Pennsylvania Derrickson followed one pair for six years. In addition to singing, a male mockingbird attracts a female by building the outer twig foundation of several nests in shrubs and trees three to 10 feet from the ground. She then chooses one of those nests and lines the cup-shaped nest with grasses, rootlets, leaves and even such trash as dental floss, laundry lint, bandages, duct tape, pieces of plastic and aluminum foil.

In southeastern Pennsylvania, a female mockingbird begins laying her three to four pale blue or greenish-white eggs spotted with red or brown in mid-April and incubates them for 12 to 14 days. The male perches on a high point nearby and guards her, the eggs, and later the nestlings from predators such as blue jays, fish and American crows, red-tailed hawks, snakes, squirrels, raccoons, opossums, cats and even humans by chasing them away from the nest. Sometimes as many as six mockingbird neighbors will join together to mob and chase away possible nest predators.

The nestlings are born naked, blind, and covered with light down. Both parents feed them 82% arthropods and 18% fruit. The nestlings fledge fully feathered at 12 days of age and can fly well when they are 20 days old. The parents feed them for three weeks more, but the male often takes complete charge if the female starts refurbishing another nest and laying eggs for a second brood.

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

Immatures never breed on their natal territory and can disperse up to 200 miles which may be how what used to be mainly a bird of the southern United States in the early nineteenth century has become a bird that nests as far north as southern Canada.

In Pennsylvania mockingbirds have been moving northward since the 1950s, although avoiding densely forested areas across the northern tier. They are still most common in southeastern Pennsylvania but are also plentiful in the Ridge-and-Valley Province and in southwestern Pennsylvania including the Pittsburgh Low Plateau. Altogether, the state has an estimated 200,000 singing males so we should have no trouble hearing even more of the mockingbirds in years to come.

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

Fishy Crows

Posted on October 1, 2021 by Marcia Bonta | 5 Comments

Fish crows at Great Meadows NWR, Concord, MA. Photo by Tom Murray (CC BY-NC 2.0)

“Listen. Those birds don’t sound like crows,” my husband Bruce said, “but they look like crows.”

He pointed to blackbirds perched on the light poles and flying above Wegman’s parking lot in State College.

They sounded as if they were American crows with colds in their noses, a nasal “eh-uh.” But they looked like American crows.

Later, I learned they were fish crows and that they had slightly smaller bodies, more tapered wings, faster wingbeats, and shorter legs than American crows. Such differences are almost impossible to note in the field, which is why most birders can only positively identify fish crows by their unique calls. These crows live along the Atlantic and Gulf coasts from Maine to east Texas and inland along major rivers from Pennsylvania south to Mississippi.

Fish Crow from *Birds of America* (1827) by John James Audubon, etched by Robert Havell

Fish crows were first observed along the Delaware and Schuylkill rivers in Philadelphia by Scottish ornithologist/artist Alexander Wilson, who named them Corvus ossifragus in 1812. And ornithologist/artist John James Audubon mentioned seeing them in the 1830s along the Delaware River almost to its source. By 1903 they were nesting in small Philadelphia parks including a park across from the Academy of Natural Sciences, where the fish crows stole skeletons that taxidermists had put out to bleach on the roof.

Since then, they have moved up all our major and minor river valleys north and west including, in the last couple decades, the Ohio River drainage.

Like American crows, fish crows are opportunistic. Not only have they expanded their habitat from coastal marshes and beaches to lakes and rivers but also to farmlands, wooded neighborhoods, and suburban areas.

Their food choices are omnivorous—carrion, trash, berries and other fruits, grain, crabs, turtle eggs, and nestlings and eggs of songbirds such as blue jays, red-winged blackbirds, brown thrashers, common grackles, and northern mockingbirds and water birds including herons, gulls, ducks, plovers, rails, terns, and double-crested cormorants. They even will nest in heron colonies and raid their nests, and when they find a good source of food, they may cache it to eat later or to feed to their nestlings.

If they migrate at all, it is only to good sources of food such as landfills, feed lots, and malls and shopping centers with accessible dumpsters. They usually join winter roosts of American crows but return to their breeding grounds as early as February in Pennsylvania.

Fish crows are monogamous and have no courtship displays, although Kevin McGowan, who studied them in Florida, wrote in his Birds of the World account that he observed “a nest-building crow with stick in its bill flying slowly with stiff wings in exaggerated ‘butterfly fashion’ circling nest site completely before going to nest, repeated several times,” but whether or not that was a courtship display has not been determined. However, mated pairs do preen the back of each other’s heads.

Fish crow with nest under construction – photo by Andy Reago & Chrissy McClarren (CC BY 2.0)

Both sexes build their nest in tall trees as high as 80 feet. It takes them approximately nine days, although they start several nests before lining and finishing one. They may use the same tree sometimes for years, but they always build a new nest of deciduous tree sticks and line it with soil, red cedar, or grapevine bark, hair and/or pine needles. The finished product is 19 inches across with a cup of five inches.

Here in Pennsylvania fish crows may build a nest as early as April 11 or as late as June 29. They have a small territory around their nest tree, and occasionally they will breed semi-colonially among several other fish crow pairs with nests within 100 yards of each other. The male fish crow defends the nest site from American crows, but he will often allow other fish crows to approach his nest.

The female fish crow lays two to six pale bluish-green eggs marked with brown which she incubates while the male guards and feeds her, bringing food in his throat not his bill, both for his mate and later his nestlings.

Red-tailed hawk being mobbed by fish crows in Brooklyn – photo by Will Pollard (CC BY-ND 2.0)

Both mob possible nest predators, most notably hawks, raccoons, owls, and humans. After the eggs are incubated for 16 to 19 days, the naked, helpless young emerge and take 32 to 40 days to mature and fledge.

Fish crows have not been studied as much as American crows but like their congeners they are curious, intelligent and social birds that will play with objects they find. However, they can be aggressive toward each other, for instance, a fish crow at a garbage site was observed pulling the tail of another fish crow which then flew away.

More serious fights begin with threatening posturing, during which they arch their necks, hold their heads forward and point their bills downward, spread their tails, slightly spread their wings or keep them close to their bodies with their wing tips down, and walk sideways toward their opponent. After fights, they perform an appeasement display consisting of open-mouthed begging calls, lowering their bodies and quivering their extended wings, and they always give in to American crows in fights.

Although I can easily see and hear fish crows in State College and on the Penn State campus where they roost in the winter and breed locally, I have yet to see and hear them in my own Blair County. But other folks have because the fish crows have come by way of the Frankstown Branch of the Juniata River into our county. The first record was April 15, 2006 by Roy Boyle at the north end of Altoona.

Fish crow at Camman’s Pond, Long Island – photo by Beth Fishkind (CC BY-NC-ND

Closer to our home on Brush Mountain in northern Blair County, our son Mark heard a fish crow in Sinking Valley below our mountain in April 2015 and frequently saw them in the springs of 2016 and 2017 over the farmland between Tyrone and Bellwood and on the wetland behind the Northern Blair County Recreation Center.

The following July (2018) Mark and our other birder son Steve were sitting on our veranda when they heard a fish crow call as it flew above Sapsucker Ridge. Then from March 19 until July 14, 2020 Mark saw fish crows along the Little Juniata River at the base of our mountain. His highest number was 12 on March 19. And the most he saw fly over our farm together were six fish crows on March 31. But most days he had one or two throughout the spring, summer, and as late as October 9. Clearly they were attracted by the river.

While in Pennsylvania the highest number of fish crows are in the lower Susquehanna River valley in the counties of York, Cumberland, and Lancaster and along the lower Delaware River and its tributaries, they have greatly expanded their range from the first to the second atlasing of Pennsylvania breeding birds according to Douglas A. Gross. They are “strongly associated with pasture in Pennsylvania,” he wrote in the Second Atlas of Breeding Birds in Pennsylvania. Since they are scarcely ever above 1000 feet and rarely ever in densely forest areas, I can’t expect to see them breeding in our tall trees at 1200 feet in elevation, but they have increased 86% in the number of blocks of fish crow records from the first Atlas of Breeding Birds in Pennsylvania. Their state population is estimated to be about 30,000 and nationwide 450,000 according to Partners in Flight. Even though West Nile virus killed many in the early 2000s, their numbers have recovered. But as Gross concludes, “Although it [fish crow] has made advances, it is not nearly as common and widespread as the seemingly ubiquitous American crow.”

Little Brown Bats

Posted on August 8, 2015 by Marcia Bonta | 2 Comments

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

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

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

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 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

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

Posted on July 15, 2015 by Marcia Bonta | Leave a comment

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 (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 (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 (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.

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 (Paul Hurtado – CC licence)

Marcia Bonta

naturalist writer

Category Archives: Animal Behavior

The Many-Tongued Mimic

Fishy Crows

Little Brown Bats

Amazing Hooded Warblers

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