I See Change

Everyone sees change over their lifetime. I certainly have.

The main house and, to the left and partially hidden by some trees, the guest house (Photo by Dave Bonta on Flickr)

The main house and, to the left and partially hidden by some trees, the guest house (Photo by Dave Bonta on Flickr)

This year was my 45th living on our mountaintop property in central Pennsylvania. My husband Bruce and I also celebrated our 54th wedding anniversary. The three sons we raised on this mountain are middle-aged and we are old.

During our tenure here we have seen many changes, both good and bad. Now that the trees are leafless these bleak December days, every time we drive our mile-and-a-half hollow road, we notice how close to death the hemlocks are that line the stream.

Since we moved here in August of 1971, we have lost a couple tree species, first a scattering of butternuts, followed by American elms. Now our hemlocks and ashes are succumbing to the insects and diseases that have come from abroad.

Dead mountain laurel in Plummer’s Hollow (Photo by Dave Bonta on Flickr)

Dead mountain laurel in Plummer’s Hollow (Photo by Dave Bonta on Flickr)

Once Laurel Ridge had a thick understory of mountain laurel shrubs that provided nesting habitat for a variety of songbirds, especially wood thrushes, as well as cover for white-tailed deer. Every June we had a glorious wild garden of blooming mountain laurel that stretched for miles on the ridge, but now many of the shrubs are twisted skeletons with few or no leaves clinging to them, dying or dead of a leaf fungus.

Other native shrubs and tree saplings are white-tailed deer preferred food, and like well-trained botanists, they are able to tell the natives from the invasives, rejecting Japanese stiltgrass, barberry, privet, and garlic mustard, for instance, and browsing on maple-leaf viburnum, wild hydrangea, rhododendron, red-berried elder, oak, black gum, and flowering dogwood seedlings and other natives. Our son, Dave, encloses every native shrub and tree he plants in his yard and ours with a fence until they rise above deer level.

Orange jewelweed (Photo by Dave Bonta on Flickr)

Orange jewelweed (Photo by Dave Bonta on Flickr)

Those are the bad changes, but we still have over 200 species of wildflowers, 150 of which are natives. Wood nettle, which first appeared back in 2006 along our stream, has rapidly spread in the woods, creating a thick cover that keeps stiltgrass out. Jewelweed, also called touch-me-not, does the same where it is allowed to thrive. And the tree species that are still disease-free, including white and red oaks dating back to 1812, are growing larger every year.

Since we moved here, songbird numbers have been cut in half throughout the continental United States. Even though we provide nesting habitat for at least 71 songbird species, we have far fewer of most species, such as wood thrushes, or have lost golden-winged warblers despite perfect habitat at the edges of First Field.

Habitat loss both on their nesting and winter grounds has been and continues to be a major problem. In the heavily populated eastern United States, roaming domestic cats, window strikes, and lately the many wind installations on mountaintops and along the Great Lakes where the birds migrate are big killers of birds.

Little brown bat with white-nose syndrome

Little brown bat with white-nose syndrome (Photo by Ryan von Linden/New York Department of Environmental Conservation/U.S. Fish and Wildlife Service on Flickr, Creative Commons license)

The wind farms are even worse for our dwindling bat population, especially our cave bats, which are already dying from the dreaded white-nose syndrome, brought here from Europe less than a decade ago where the bats have built up a resistance to the disease over many centuries. Not many people care about bats because they are ignorant of their amazing mosquito-killing abilities. Just last August our son Dave and his partner, Rachel, were lying out in First Field watching a meteor shower. Rachel is highly allergic to mosquito bites and was delighted that three bats continued to flutter above them eating mosquitoes.

Last summer I had the opportunity to educate one woman, who owns an old, Victorian mansion she has turned into a tea house and bed and breakfast, about the disease. She and her husband were tender-hearted enough to shoo the occasional bat out of their house instead of killing it but had no idea about the disease killing them. When I gave her the statistics though—99% of most bats dead in their hibernating caves and the disease spreading rapidly across the United States and Canada, she was appalled. When I added that a female bat has only one pup a year, she understood why most scientists believe it will be 500 years, if ever, that cave bats will recover the numbers they had before the disease, and that some of the already rare species, such as Indiana bats, soon may be gone forever.

The hacking tower on Haldeman Island in 1989 (Bruce Bonta photo)

The hacking tower on Haldeman Island in 1989 (Bruce Bonta photo)

Still, through all this litany of loss I have seen terrific success stories here in Pennsylvania over the years, and many are due to the work of the Pennsylvania Game Commission. Back in the nineteen seventies, eighties, and even nineties, seeing ospreys, peregrine falcons, and bald eagles were rare and treasured experiences. I remember visiting Haldeman Island and watching the workers feed the young bald eagles they were raising before releasing them in the hope that they would thrive and return to breed in Pennsylvania. I also talked with and watched biologists monitoring peregrine falcons breeding on bridges over the Delaware River.

Today you can watch peregrine falcons nesting in our cities on webcams and seeing osprey and bald eagles is possible in many areas of our state. A couple summers ago, while hiking at a nearby state park, Bruce and I watched an osprey catching fish in the lake. And a pair of bald eagles now nest at the other end of our mountain. This raptor-recovery from the DDT years has been an unexpected pleasure for those of us who sit on mountaintops in fall and watch a steady procession of them heading south.

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

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

When we moved here, we observed what we thought were a wide variety of mammals—woodchucks, gray squirrels, eastern chipmunks, porcupines, raccoons, gray and red foxes, white-tailed deer, striped skunks, opossums and several vole, mice, and shrew species.

Then, in 1983 we had our first black bear sighting and in 1989 our first eastern coyote. In this century both species have become far more common, breeding and living on the mountain year round. Bobcats have always been rare but present. Our sons saw one in the 1970s as they walked up our road from school, and I glimpsed another in January of 1990. I long for a better view of this elusive species, but several of our hunters sitting in their tree stands have had longer sightings of bobcats.

A beaver near our house in Plummer’s Hollow, February 2000 (Photo by Bruce Bonta)

A beaver near our house in Plummer’s Hollow, February 2000 (Photo by Bruce Bonta)

Although we’ve never seen an otter here, despite the successful increase in their population due to Pennsylvania Game Commission biologists, during the winter of 2000 we did have an enterprising beaver swim up our flooded, first-order mountain stream a mile and a half, probably in search of a new home. This century we have also seen an increase in mink, long-tailed and short-tailed weasels, but I never suspected that we would see fishers on our property when I visited with the PGC researcher back in the nineties and she took me on a whirlwind tour of northcentral Pennsylvania where the PGC had recently released the animals.

The fishers were supposed to stay north of Interstate 80, but apparently they didn’t know this, so imagine my disbelief when I spotted one beside our stream in September of 2005. Since then our caretaker family and I have had several more sightings of these beautiful animals.

Our north-facing access road on January 28, 2008 (Photo by Dave Bonta on Flickr)

Our north-facing access road on January 28, 2008 (Photo by Dave Bonta on Flickr)

“I See Change” is the name of a website you can access and record the changes you have seen in your natural world. In addition to the changes I have seen in our plants and wild creatures, I’ve also noticed a change in our seasons. For more than two decades, all the leaves were off the trees by the first of November, and winter began near Thanksgiving with the first snowfall. Shortly after that, I did not drive down our north-facing access road until the beginning of March when it melted.

In this century, the oaks hold their leaves until mid-November, and cold weather and snow comes as late as Christmas or even early January. Then spring, instead of starting slowly in March, doesn’t start until April except for a warm spell that prematurely brings out tree blossoms and then freezes again. Finally, May warms up quickly to summer temperatures and early June ushers in true summer. Spring is my favorite season, and it seems to be shortened on either end, whereas autumn goes on and on often through rifle season and beyond.

Spring beauties (Photo by Dave Bonta on Flickr)

Spring beauties (Photo by Dave Bonta on Flickr)

Even though the seasons seem to have shifted by two weeks or more in both late fall and early spring, 1988 still remains the hottest summer we have ever experienced here and the winter of 2014-15 one of the coldest and snowiest despite its late start.

I know all this and more because of the detailed nature journal I’ve been keeping since 1971. I don’t only see change, I know change. On balance, our years here have been a joy despite the loss of tree species and bats and the increase in invasive plants. Every time I see a bear, coyote, fisher, or bald eagle, I am grateful for the positive changes. I look forward to more years of nature-watching and close encounters with the many creatures with which we share our mountain.

 

Food for Wildlife

After three lean years, our oak trees finally produced a bumper crop of acorns last September. Forewarned by hordes of blue jays screaming from the treetops as they plucked ripe acorns from the oaks, I had to be careful on our steep trails not to slide on the fallen nuts that were more hazardous than marbles.

grey squirrel

Grey squirrel eating an acorn (Juraj Patekar image on Flickr, Creative Commons license)

Still, not every section of forested Pennsylvania had a good acorn crop, despite predictions from folks that should know better. Dr. Marc Abrams, a forestry professor at Penn State says there’s “no way to predict it,” calling a heavy mast year “one of the amazing mysteries in nature that we still do not have a handle on.”

Dr. Warren G. Abrahamson, a Bucknell University professor who conducted a long term study of acorn production from 1969 to 1996 with Jim Layne of the Archbald Biological Station in Florida, agrees, although he says that “the production of acorns definitely is not forecasting but hind casting the weather.” In their September 2003 report of their work they claimed that the size of the acorn crop each year is partly controlled by precipitation which affects acorns during different stages of development in prior years.

Other experts think that the group behavior of masting trees called synchrony most likely depends in part on the temperature during pollination in late April or May. Since oaks are wind-pollinated, meaning the wind must transfer pollen from staminate (male) to pistillate (female) flowers, a period of rain might disrupt the process.

For instance, a cold, wet spring in 2012 affected red oak production in 2013 because all the oaks in the black oak group (those with pointed lobes on their leaves) take two years to mature. Those in the white oak group (those with smooth lobes on their leaves) take only a year and would be affected by a late spring frost during pollination.

Still others believe that synchrony occurs as a way to outsmart nut predators by producing more nuts than the predators can eat, ensuring that at least some nuts will grow into trees. But whatever the causes, it is cyclic and occurs every three to five years.

On our dry mountaintop we have mostly chestnut oaks with an occasional white oak in the white oak group. Deer prefer these tastier acorns and squirrels eat them almost immediately because they spoil more quickly than those in the black oak group, which include scrub, black, northern red, and scarlet oaks here. Those acorns the squirrels store.

hickory nut

Hickory nuts form 10 to 25 percent of a squirrel’s diet in a good year (image by Peppysis on Flickr, Creative Commons license)

Acorns are not the only hard mast fruit. Others include the squirrels’ favorite—hickories, especially pignut, mockernut, and shagbark—which consists of 10 to 25 % of their diets in a good year and ripen before acorns. But like oaks, as well as the other hard mast producers—American beeches and black walnuts—they are also wind-pollinated.

Hard mast is high in fat, carbohydrates, and protein and is important to at least 180 species of birds and animals in fall and winter, but since it is highly variable in production from year to year, wildlife must depend also on a wide variety of soft mast throughout spring, summer, and fall. These fleshy, perishable fruits high in sugar, vitamins, and carbohydrates include a wide variety of native trees, shrubs, and woody vine species.

Foresters and wildlife biologists, in fact, consider mast to be the woody plant fruits and browse of native trees, shrubs and vines even though the word mast comes from the Old English “maest” which meant the forest tree nuts on the ground that fattened domestic pigs and other animals.

A wide variety of soft mast allows many mammals and birds to survive the lean years of hard mast. Of course, there are always some nuts every year, but ever since the extinction of American chestnut trees which, because they were insect-pollinated and didn’t bloom until summer, reliably produced an excellent crop of nuts, wildlife has had to adjust to a feast or near famine hard mast situation.

Consequently, encouraging biologically diverse meadows and forests, stocked with native trees, shrubs, and woody vine species produces food for wildlife throughout the year. And diverse food leads to diverse wildlife, as we’ve discovered on our property.

Other examples of trees that are insect-pollinated and produce a huge number of seeds every year as well as foliage, twigs and bark are red and striped maples. Striped maple, also called moosewood or goosefoot, has fruit that matures in early fall and is eaten by ruffed grouse, rodents, and songbirds. In addition, it produces browse for deer and bark for rabbits and beaver.

Elk eat the buds, foliate, twigs and bark of red maple, songbirds gorge on the seeds, and squirrels and mice store them for winter.

Basswood is another insect-pollinated tree, producing seeds squirrels and chipmunks consume while deer and rabbits browse its foliage.

The best of the soft mass fruit is that of wild black cherry trees. It fruits abundantly every third or fourth year in August and is pollinated by solitary bees. Seventy bird species feed on the fruit including grouse and wild turkeys. Black bears, raccoons, foxes, rabbits, squirrels, chipmunks and mice relish the dark cherries.

witch-hazel fruit and flowers

Witch-hazel fruit and flowers (Image by Rodger Evans on Flickr, Creative Commons license)

The fruit of sassafras trees, which is high in fat, is eaten by turkeys, bobwhite quail, black bears, pileated woodpeckers and gray catbirds. Rabbits and deer browse its twigs, black bears like its stems and deer its leaves. Despite its popularity, we have many sassafras trees in our forest.

Common witch-hazel, which flowers in late fall, develops woody capsules the following spring and summer. Those capsules contain a pair of shiny, black hard-coated seeds that shoot out in autumn before the next flowering. But squirrels, turkeys, quail, and grouse go after them, especially if the acorn crop fails. Deer browse heavily on witch-hazel, but it persists in growing above the deer line here.

Common spicebush (my personal favorite) produces brilliant spicy red fruits eaten by grouse, pheasants, and quail. It also provides shoots for rabbits and browse for deer, but it too survives and thrives, especially in wet areas along our stream. Our son Dave has planted it as an attractive shrub in our yard and his.

Both red-berried elder, which blooms the same time as the invasive barberry, has red berries available for birds in June or early July, although it only lives on steep slopes here because deer are fond of its browse. Deer also like common elderberry. It blooms in late June or early July and hangs heavy with clusters of dark purple berries favored by birds and humans in late August.

White-throated sparrow with staghorn sumac fruit

White-throated sparrow with staghorn sumac fruit (Kelly Colgan Azar photo on Flickr, Creative Commons license)

Staghorn sumac is making a recovery on our property, living on the sunny edges of meadows and forests. Blooming in late June and early July, its greenish-yellow, fragrant flowers morph into bright red, cone-shaped clusters of fruit that last through the winter, providing food for squirrels, songbirds, grouse, pheasants, turkeys and quail. Deer and rabbits browse on this shrub as well.

Wild berries are a popular summer food. First come the lowbush blueberries as early as mid-June on our powerline right-of-way, followed by the huckleberries. Black bears are particularly fond of them, but so are songbirds, grouse, chipmunks, pheasants, and mice.

Black raspberries ripen in early July and blackberries in early August. Both are incredibly important fruit for songbirds, skunks, opossums, foxes, squirrels, chipmunks, and black bears, while rabbits like their cover and rabbits and deer browse on their stems. Of course, the wildlife must also compete with me, especially in the blackberry patches.

Opossum eating wild grapes

Opossum eating wild grapes (photo by pverdonk on Flickr, Creative Commons license)

Greenbrier of several species has bluish-black berries eaten by songbirds and gamebirds and deer browse them. They browse wild grapevines too, but wild grapes are among the most important and valuable food for wildlife including songbirds, gamebirds, foxes, skunks, raccoons, opossums, squirrels and deer. The vines provide winter shelter for animals and birds too. I remember one winter when the hard mast failed and deer spent the season among the grapevines of the Far Field thicket, yarding up like they do in northern New England.

My list of native trees, shrubs and vines could be greatly expanded. In other parts of Pennsylvania, particularly south of us, still other wildlife food, such as common papaws, are important. But diversity remains the key to providing abundant wildlife food, even in years when hard mast is scarce.

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)