A Walk in Penn’s Woods

Last autumn, on a hot, humid Sunday afternoon in early October, my son Dave and I led a Walk in Penn’s Woods on our property. This program, begun in 2017 by the Center for Private Forests at Penn State, has attracted support from both private and public land owners eager to share their forests and the trees, shrubs, wild flowers and wild creatures that inhabit them.

Black birches in Plummer’s Hollow

Black birches in Plummer’s Hollow (Photo by Dave Bonta on Flickr)

Our walk was the only one scheduled in Blair County, and we did not advertise it ahead of time. Still, we had one man from Centre County, another from our county, and a couple from Indiana County.

From our 10 miles of trails, Dave and I had chosen the walk up our mile-and-a-half entrance road paralleling our Plummer’s Hollow stream, through a mostly diverse hardwood forest that also has a stand of hemlocks affected by hemlock woolly adelgids. Many of the trees in the hollow date from the 1840s when it was last clearcut to feed the iron furnace at the base of our road known as Upper Tyrone Forge.

Since visitors to our property first drive across an old couty bridge over the Little Juniata River and then bump across the main railroad line from New York to California, we are able to point out the remnants of the watering tank near the bottom of our stream which was used by the steam locomotives beginning in 1850. It was first overseen by the original William Plummer who came here in 1832 to work as a forge man and ended his life working on the railroad.

Beech trees below the driveway

Beech trees below the driveway (Photo by Dave Bonta on Flickr)

Human history that impacted our forest was important, but so was learning about our forest today and the plants and animals that live in it. Because the trees are old and the understory on the steep slopes of Laurel and Sapsucker ridges fairly diverse, we were able to show our visitors a wide variety of native tree species and their fruits from cucumber-tree and American basswood to American beech, red, black, white, chestnut and scarlet oaks, white pine, sugar and red maples. All of these species and more provided dense shade that made the walk pleasant.

A Sunday afternoon in early October was not the best time to see or hear the many songbirds that live in this forest, but we could at least mention the red-eyed and blue-headed vireos, ovenbirds, scarlet tanagers, Acadian flycatchers, Louisiana waterthrushes, wood thrushes, black-throated green, hooded and worm-eating warblers and other birds nesting here in spring and summer, and the year round species such as black-capped chickadees, white-breasted nuthatches, and downy, hairy, red-bellied, and pileated woodpeckers, for instance.

Beechdrops in Plummer’s Hollow

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

The wildflower season was also waning, but I did show them blooming beechdrops, wavy-leaved asters, and blue-stemmed goldenrod. In addition, I identified native shrubs—maple-leaf viburnum, red-berried elder, wild hydrangea, spicebush, mountain laurel, and my favorite rhododendron–while Dave pointed out the various tree species.

Halfway up the road we were able to feature a large white oak growing atop the flat remains of a charcoal hearth as well as the chunks of charcoal beneath the thin layer of topsoil.

Since our goal is to let our forest mature into old growth, when trees die, we let them fall and rot to provide more soil and have so many dead snags that birds, bats, gray, fox and flying squirrels and other mammals have no trouble finding nesting holes. We also told our bear, fisher, and coyote stories and mentioned the success of the Game Commission’s program to bring back the extirpated fishers. In addition, the Commission’s efforts to increase bald eagle numbers has led to nesting bald eagles on game lands at the other end of our mountain. This was a gift we had never expected to see in our lifetimes.

We led our visitors to the base of Guesthouse Trail to point out the small rhododendron exclosure Dave had built to keep the deer away from this shrub that is a favorite of theirs especially during the winter months.

One of our deer exclosure fences showing the abundance of vegetation inside it

One of our deer exclosure fences showing the abundance of vegetation inside it (Photo by Dave Bonta on Flickr)

And finally we went on to our three-acre exclosure in a part of our forest with a white oak and several red oak trees that date to 1812. Despite our successful hunter program with excellent hunters on our land from the beginning of archery season in October to the end of flintlock in mid-January, our visitors could still see the difference between the open forest outside the exclosure and the dense understory inside including the numerous oak, white pine, black gum, and maple saplings.

In the heavily forested portion of our property, primarily on Laurel Ridge, we have little trouble with invasives, but our 37-acre meadow and the 125 acres we purchased on Sapsucker Ridge after it had been high-graded back in 1991 are infested with barberry, mile-a-minute, stiltgrass, multiflora rose and other pernicious non-native plants, most of which provide little or no nourishing food for birds and mammals, unlike our native trees and shrubs.

Invasive plants and diseases, tree, shrub, and wildflower identification, wildlife, including birds, mammals, reptiles and amphibians, and forest management seemed to be the dominant themes in the 68 walks in 48 counties attended by 1,136 people last autumn.

For instance, at the 50-acre Laura Olsen Memorial Sanctuary walk in Crawford County, hosted by Presque Isle Audubon Society and the Foundation for Sustainable Forests, they entitled their walk “Exploring Forest Bird Habitat” where as many as 51 species have been documented in this forested wetland.

The Musser Gap walk in Centre County, which attracted 66 participants, had 10 stations leading into Rothrock State Forest. There were handouts at the parking lot and leaders at every station that covered forest management, natural or cultural topics.

The Pennypack Ecological Restoration Trust in Montgomery County led a walk around the wooded areas of Pennypack Creek that featured a native persimmon tree with fruit and the fruit of a black walnut tree. Visitors saw an American kestrel and sharp-shinned hawk and identified bird and animal calls. The leaders explained why they had wrapped trees in preparation of the deer rut. At a pond everyone heard frogs and saw a beaver lodge.

A Walk in the Woods in 2018 on the Jackson’s property, Bedford County

A Walk in the Woods in 2018 on the Jackson’s property, Bedford County (Photo by Laura Jackson, supplied by the Center for Private Forests)

In Bedford County, Mike and Laura Jackson led 22 people over their mostly wooded property. They walked through part of their woods that was high-graded back in the 1980s and talked about how that type of logging creates an unhealthy forest. They pointed out invasive species and the impact of too many deer on the forest even though Mike does his best during hunting season.

They also have a shelterwood cut that was done in the autumn of 2014 and enclosed by an eight-foot-high fence. On a trail through the exclosure, they identified the native trees and shrubs that have appeared such as sassafras, both hornbeam species, and quaking aspen in addition to stump sprouts of tulip poplar, black cherry, oak, elm and red maple that are already almost 20 feet tall.

The large seed trees that were left after the shelterwood cut included shagbark and pignut hickory, black cherry, sugar maple, tulip poplar, white and red oaks, butternut and American basswood, all of which provide excellent wildlife food.

Another view of the 2018 walk on the Jackson property

Another view of the 2018 walk on the Jackson property (Photo by Laura Jackson, supplied by the Center for Private Forests)

That was the second Walk in Penn’s Woods the Jacksons’ hosted. On each walk, like most folks on these walks throughout the state, walkers were interested in learning how the Jacksons have managed their woods for wildlife and what birds and animals live there.

In Lancaster County the Game Commission’s Middle Creek Wildlife Management Area sponsored a walk on a nature trail with 10 stations featuring wildlife and forest management techniques and tree identifications.

State Game Lands #37 in Tioga County, hosted by the Tioga County Group Effort, attracted 27 people who learned about game food plots, timber harvesting, wildlife and general forest management principles.

Young and old enjoying a walk in the woods at the Montour Preserve, Montour County

Young and old enjoying a walk in the woods at the Montour Preserve, Montour County (Photo by Henry Williams, supplied by the Center for Private Forests)

A few of the walks were stroller and wheelchair accessible and, as such, attracted over 30 people. One was in Montour County at the Montour Preserve where they were led on the Goose Woods Trail by Jon Beam who has been associated with this preserve for decades and once showed me the signs of American woodcock during a visit.

At Tuscarora State Park in Schuylkill County 33 people walked on a wheelchair-accessible paved path around Tuscarora Lake where they learned to identify the trees and shrubs of this forest and were told about the forest benefits to humans and wildlife.

Two young people participating in a Walk in the Woods at the Wolf Creek Narrows Natural Area in Butler County

Two young people participating in a Walk in the Woods at the Wolf Creek Narrows Natural Area in Butler County (Photo by Andrew Zadnik, supplied by the Center for Private Forests)

Because of the popularity of wheelchair and stroller accessible walks, this year’s organizers of the Walk in Penn’s Woods on October 6 hope to have more such walks in what they are calling Walk and Roll in Penn’s Woods. But many of the same walks as last year plus new walks are featured on their website.

For most walks there is no reason to sign up ahead of time. Just pick your walk anywhere in the commonwealth and go. You are bound to learn something new about Penn’s Woods and meet knowledgeable people both leading and attending the walks.

 

 

Aeroecology

As the days shorten, birds begin to migrate long before cold weather sets in. I notice the first flush of migratory birds on our mountain sometime in mid-to-late August. But September and early October are the peak months here for bird migration.

Migrating snow geese near the Middle Creek Wildlife Management Area

Migrating snow geese near the Middle Creek Wildlife Management Area (Photo by the Chesapeake Bay Program on Flickr, Creative Commons license)

Now that they are on the move, birds enter the most dangerous phase of their lives, especially the immature birds that have never migrated before. They need safe places to land and forage, what ecologists call “habitat,” both water and land-based, depending on whether they are songbirds, raptors, waterfowl, or shorebirds.

Although researchers have made progress in studying how birds migrate, using the stars at night and landforms during the day, for instance, as well as what they eat and where they forage on land, they know less about what happens when the birds are airborne, especially when they encounter human activities.

A barn swallow in flight at the John Heinz National Wildlife Refuge

A barn swallow in flight at the John Heinz National Wildlife Refuge (Photo by Stan Lupo on Flickr, Creative Commons license)/

But in the last decade some ecologists maintain that since birds spend much of their lives in the air foraging, migrating and sometimes even mating, especially swallows and swifts, airspace should also be considered habitat, not only for birds, but bats and a wide variety of flying and even migrating insects such as butterflies and dragonflies.

While there was some discussion of airspace as habitat early in this century, it was a paper written in 2013 entitled “The Airspace is Habitat” by research ecologist Robert H. Diehl that launched the new study called “aeroecology.” Diehl, who studies migratory birds at the United States Geological Survey’s Northern Rocky Mountain Science Center, cited numerous definitions of habitat by several well-known ecologists. He summarized their contention “that occupancy, and perhaps resource use, are essential attributes of habitat,” and concluded that, ”airspace satisfies these criteria.”

Since Diehl’s ground-breaking but brief paper, numerous studies have been done on all aspects of airspace and its importance in the conservation of birds, bats and flying insects.

A wood thrush killed by striking a window

A wood thrush killed by striking a window (Photo by Bob on Flickr, Creative Commons license)

Studies show that up to a billion birds a year die in the United States when they fly into the windows of homes and office buildings, the most common and numerous obstacles in their airspace, according to the American Bird Conservancy. In addition, seven million fly into communication towers, although the latter number may decline since the Federal Communications Commission issued guidelines suggesting that tower operations switch from steady-burning to blinking lights that are less confusing to birds.

Then there are the wind turbines that kill many species of birds and bats that fly into the huge, rapidly-spinning blades. Unfortunately, many of those turbines have been built in the very places where birds and bats migrate, taking advantage of the wind. Here in our area, the leading Allegheny Ridge, a proven migratory highway, has dozens of wind turbines erected on it and more to come in the future. To its credit, the Pennsylvania Game Commission does not allow wind turbines on game lands but plenty of private and local government-owned landowners in Pennsylvania do.

Wildlife biologists collecting and recording migrating song birds killed by wind turbines

Wildlife biologists collecting and recording migrating song birds killed by wind turbines (Photo by kqedquest on Flickr, Creative Commons license)

Well-known birder Kenn Kaufman, in his new book A Season on the Wind, relates an on-going battle by his wife, Kimberly, executive director of the Black Swamp Bird Observatory, to keep wind turbines off Camp Perry, a military-owned property along Lake Erie in northwestern Ohio, which is next to Magee Marsh and other famous migrating bird stopovers. He writes that “wind turbines placed in the middle of essential stopover habitat” [such as the shores of Lake Erie] “are likely to kill disproportionate numbers of long-distance migrants, birds that are already pushing the limits of survival.” The same is true of Pennsylvania’s own shoreline of Lake Erie.

Furthermore, Kaufman insists, the numbers of birds and bats the wind industry claims are killed by the turbines are vast under estimates. While using the wind as a source of carbon-free electricity is necessary, it would be better for the birds and bats if the installations were smaller and local instead of massive and requiring powerlines, another threat to birds and bats, to transmit the energy.

Light pollution from human-related sources such as office towers in cities is especially dangerous to night-flying and/or migrating birds. How light pollution in general affects birds is still another branch of aeroecology research. According to one scientist, artificial light can be seen as far as 224 miles on the horizon. Artificial light at night may change the ability of night-migrating birds to orient and navigate, and also change the way birds communicate and avoid predation in addition to possibly screwing up their geomagnetic sense that helps them find their way.

Tribute in Lights 9-11-2017

Tribute in Lights 9-11-2017 (Photo by Kim Carpenter on Flickr, Creative Commons license)

One study of the National September 11 Memorial and Museum’s “Tribute in Light” in New York City by a team of ornithologists over seven years found that the light changed the behavior of migrating birds at altitudes up to almost two-and-a-half miles. The birds gathered in high numbers, decreased their flight speeds, and flew in circles, all the while calling. But when the lights went out, the birds resumed their migration. The researchers agreed with other studies “highlighting disorientation due to artificial lighting” on many structures such as sport stadiums, construction sites, and offshore oil rigs. In addition, they found, ”There is mounting evidence that migratory bird populations are more likely to occur in urban areas during migration, especially in the autumn.”

Still, a variety of stakeholders in the Tribute of Light event, including the NYC Audubon and the Cornell Lab of Ornithology, agreed to keep the lights on despite its effect on the birds unless conditions were particularly hazardous and then they would shut off the lights for short periods. These shut-offs were enough for birds to continue on their way.

In Pittsburgh, every time the University of Pittsburgh football team wins a game, powerful lights are aimed high in the sky from the tallest campus building. These “Victory Lights” were on for the weekend of October 7-8, 2018 when Pitt won its game against Syracuse. At that time, nature writer and bird blogger Kate St. John was monitoring weather radar and noticed that there were large numbers of migrating birds around Pittsburgh. After she wrote about it, Pitt board members, the Pitt chancellor, and the Executive Director of Audubon Society of Western Pennsylvania agreed that the university would dim the lights for 15 minutes out of every illuminated hour so that trapped migrants could continue their journeys.

A Season on the WindSt. John was able to use weather radar to figure out the movements of migrating birds and how they react to human-related obstacles, because in 2004 the National Oceanic and Atmospheric Administration made its national weather radar data freely available to every interested person. Kaufman, for example, writes about how he and other birders check radar information on their computers every day and night during spring and fall migrations so they know when and where large pulses of migrating birds will land to rest and forage.

A wide range of other researchers, such as Jeffrey J. Buler, who runs an Aeroecology Program at the University of Delaware, uses radar data to study the effects of lighting on migrating birds and how such brightly-lit urban areas attract greater densities of migrating land birds. Such information has led to Lights Out and Dark Skies movements in Toronto, Chicago, and other major North American cities.

Still another study using radar found that migrating birds look for favorable winds and then fly in the atmospheric layers that have them. For instance, many migrating songbirds fly at night because of cooler air and less turbulence. But several studies have also been able to estimate how high most migrating birds fly in relation to human-caused collision threats.

A turkey vulture flies near an office tower

A turkey vulture flies near an office tower (Photo by Finn Maxwell Cousineau on Flickr, Creative Commons license)

The cruising altitude of songbirds averages 500 to 2,500 feet above the ground, raptors, taking advantage of the daytime thermals 700 to 3,000 feet, and waterfowl 200 to 4000 feet. In addition, tall buildings and their windows at 340 million and private residences at 253 million are the largest annual killers of migrating birds followed by powerlines (22.8 million), communication towers (6.6 million) and wind turbines (366,000).

This may be why some studies maintain that “a songbird is 15 times more likely to die during migration than during its long stays in its summer and winter territories,” Kaufman writes. And why some researchers in aeroecology are moving into what they call “aeroconservation” in order to keep not only the birds but the bats and the flying insects they eat safe as they navigate our crowded skies.

 

Going, Going, Gone

August is mostly hot and humid, but every year there are more and more mosquitoes. Many people blamed the excessive rain in the spring and summer of 2018 for the massive numbers of mosquitoes and black flies. It was almost as if we were living in the North Woods.

Wood frog tadpoles

Wood frog tadpoles (Photo by Brian Gratwicke on Flickr, Creative Commons license)

Our vernal ponds on top of Sapsucker Ridge became permanent ponds that provided adequate breeding places for mosquitoes once the hundreds of wood frog tadpoles metamorphosed and leaped away into the woods in late May and early June.

Other conservationists I talked with agreed that even the smallest vernal ponds didn’t dry up in late spring as usual. But while I agreed that our record-breaking wet year was partially responsible for the large mosquito population, I didn’t think that was the whole story.

The invasive white-nose syndrome, a fungal disease brought accidentally to a New York state cave in 2007 by Europeans, has killed 99% of our little brown bats in a few years. Previously we could sit outside on our veranda at dusk and watch as the bats flew overhead eating mosquitoes. Now that they are gone and despite the best efforts of biologists throughout the United States, all cave bat species will not recover to anywhere near their previous numbers for a century or more. Consequently, mosquitoes are so bad here that sitting outside on our veranda in the evening is only a fond memory.

White nose syndrome on a little brown bat

White nose syndrome on a little brown bat (Photo by Marvin Moriarty/ U.S. Fish and Wildlife Service on Flickr, Creative Commons license)

The country church at Canoe Creek State Park that once housed a nursery colony of as many as 22,642 mostly little brown bats, now has 250 mostly big brown bats that have not been as susceptible to the disease.

A Blair County mine, gated by the Pennsylvania Game Commission, held 30,000 or more little brown bats before 2010, when white-nose syndrome was first detected there, but in 2015 it had a mere 54 of them, in 2018 it had 290, and last winter 150, according to PGC biologist Greg Turner.

“Each bat eats nearly one million insects a year,” Turner says in an email. And little brown bats, once Pennsylvania’s most common bat species, specializes in mosquitoes, according to Melvin Tuttle, founder of Bat Conservation International.

Many folks believe that nature can easily recover from such losses, but while killing coyotes, for instance, will encourage them to produce more offspring, a little brown bat female can produce only one pup a year.

Ruffed grouse tracks in our woods in the winter of 2007

Ruffed grouse tracks in our woods in the winter of 2007 (Photo by Dave Bonta on Flickr)

Our plague of mosquitoes may also be carrying West Nile virus because we used to have a good population of ruffed grouse. Last spring, although my son Dave and I monitored all the places where we used to hear drumming in the spring on our 648 acres, we heard none. The days of being detained while driving down our wooded mountain road by displaying ruffed grouse or being stopped on our Far Field Road or First Field Trail by distressed females as their little, pale yellow, powder-puff chicks ran off and hid are over.

Insects from abroad are also wreaking havoc on our hemlock and ash trees. Although the hemlocks are dying a slow death instead of a fast one, probably because of occasional below zero winter temperatures that kill off many hemlock woolly adelgids, our ash trees have succumbed quickly to the emerald ash borers. Everywhere I walk on our land I see dead ashes where only a few years ago they were thriving and attracting songbirds, wild turkeys and squirrels to their winged seeds.

As if all the invasive insects and diseases aren’t enough to keep scientists busy, we are faced with an onslaught of invasive plants that are overwhelming our fields and forests. Every spring I pull out as many garlic mustard plants, a European invasive, from our primary forest as possible especially from our mile-long road bank that harbors a wide variety of native wildflowers and shrubs.

Japanese stiltgrass came in with the logging trucks on our neighbor’s adjoining property (now ours), and we didn’t realize the danger of this annual grass from East Asia, also known as Asian stiltgrass and Chinese packing grass. In fact, the dried grass filled with seeds was accidentally introduced in packing material for Chinese porcelain in Tennessee back in 1919.This one to two-foot tall weed forms a dense mat that smothers any small plants or seedlings in open areas in our forest and fields.

Japanese barberry in its autumn coloration

Japanese barberry in its autumn coloration (Photo by James Gaither on Flickr, Creative Commons license)

The 120-acre logged area we purchased in 1992 has since filled up with invasives including Japanese or red barberry, a Japanese native shrub introduced in the late 1800s in the United States as an ornamental. It forms dense stands that shade out and displace native species. Not only is it two to six feet high, but it can reach that width as well. In addition to spreading in the logged land, it also managed to invade our three-acre deer exclosure when a large maple tree came down in a wind storm, creating an opening in this section of our forest.

Yet in a 40-acre section of forest on Sapsucker Ridge that came down in an ice storm, not one barberry germinated. As I walk our trails, observing where various invasives take hold, I often puzzle about why this spot and not that one and know that the answers are complex as are most puzzles in the natural world.

Last September, while walking Butterfly Loop around the edge of our First Field, also hedged with barberry below the wooded ridge, I noticed iridescent blue fruit growing in terminal clusters from a vine hanging on a black locust tree. It had triangular-shaped leaves and downward curving spines on stems and leaf veins. To my horror, I identified it as mile-a-minute, still another invasive from East Asia.

Mile-a-minute grows in moist, sunny locations along road sites, rivers and stream banks, powerline right-of-ways and disturbed forest sites. I immediately ripped out all the plants I saw at the top edge of First Field and quickly discovered that its vine-like stems grow up to 20 feet long.

The next day, when I walked Greenbrier Trail through the logged area, I saw acres of mile-a-minute covering many barberry shrubs like shrouds. An invasive on top of an invasive. That was a first for me. I started yanking it out, but after an hour I gave up. There was far too much of it for me to remove. If only I had noticed it sooner.

Jetbead

Jetbead (Photo by Katja Schulz on Flickr, Creative Commons license)

With that lesson in mind, I finally identified the beautiful shrubs with lovely, white, four-petaled, two-inch-wide flowers at the base of our mountain as jetbead. Again from East Asia and again introduced as an ornamental to the United States in 1866. Named for their clusters of red, bead-like fruits that turn ebony, they create a thick shrub layer in forests that displace native shrubs and shade out understory species, such as tree seedlings.

I started pulling out the shrubs and quickly realized that there were more than I could handle. Our caretakers have taken over the job and have nearly eradicated it.

Greater celandine

Greater celandine (Photo by Matthew Beziat on Flickr, Creative Commons license)

To reach our road, we cross a county bridge over the Little Juniata River and drive a couple hundred feet on a gravel township road where folks often dump cuttings from their gardens. That small section of roadside harbors numerous invasives such as English ivy and greater celandine. The latter plant has bright yellow, poppy-like flowers in May and June. Also known as “rock poppy” and “devil’s milk,” it comes from Europe and Asia and can outcompete native plants.

A friend had warned me years before that it was invasive so when I found several dozen plants growing on the Far Field Road bank, more than two miles from the colony along the township road, I regretfully yanked every plant out by the roots. So far, none have returned. A small victory indeed when stacked up against the dozens of invasive plants, insects, and diseases plaguing our fields and forests.

I never thought, at my advanced age, that I would see so many permanent changes on our land, primarily due to foreign trade and travel. Furthermore, I see little hope in eradicating these plagues here during my lifetime.

A male hooded warbler in Union, Pennsylvania

A male hooded warbler in Union, Pennsylvania (Photo by Dave Inman in Flickr, Creative Commons license)

One day, in late August, I walk over to Greenbrier Trail and hear a singing hooded warbler. Then I notice a native Hercules’ club in green berry. I drop down to Ten Springs Trail where I find the trail bank is filling in with native maple-leaf viburnum shrubs and white wood asters. Walking back up our road, I discover a blooming turtlehead beside the stream. There is still much native beauty and wildlife on our mountain and I am grateful.

 

Purple Martins

One mid-July afternoon near our barn, our son Steve watched two purple martins insect-catching high in the sky. Several days before, down in nearby Sinking Valley, Steve had driven up a private road called Purple Martin Lane and found two large purple martin houses set up by a local Amish family.

The entrance to Purple Martin Lane in Sinking Valley

The entrance to Purple Martin Lane in Sinking Valley (Photo by Bruce Bonta)

“There were at least 50 purple martins using them,” he told me.

The martins he identified here were the 173rd bird species for our mountaintop property, and Steve thought they had come from the Amish farm he had visited because it was only a few miles away as the crow (or martin) flies.

The next time I drove to the valley I looked more carefully for purple martin houses and found two more Amish farms, out in the open, with two active martin houses.  Only one of each had four gourds hanging below, but I learned from Amish friends that they were growing more gourds for those Amish and other interested farm families to use as purple martin housing.

Purple martin housing

Purple martin housing (Photo by Adam Woodis on Flickr, Creative Commons license)

Purple martins live throughout North America, but those in the eastern part of the continent are wholly dependent on housing provided by humans. That’s because Native Americans fashioned homes for them from hanging gourds and pioneering farm families did the same. Both were interested in these large swallows that specialize in flying insects especially the flies that swarmed over their game and other food. This thousand-year human/martin relationship led to a remarkable trust on the part of purple martins toward humans, so much so that researchers believe purple martin housing should be erected within 100 feet of a human dwelling and 40 feet from the nearest tree.

Pennsylvania is close to the northeastern edge of the contiguous range of purple martins even though they nest as far north as southern Canada. Between Pennsylvania’s first and second atlasing periods, the martin population “contracted dramatically” according to John Tautin, writing in the Second Atlas of Breeding Birds in Pennsylvania, with losses most notably in northeastern and southwestern Pennsylvania, and central Pennsylvania’s Mifflin and Juniata counties. However, as I discovered, martins are more common in Pennsylvania where there are Amish farms.

A pair of purple martins on an Amish farm in Pennsylvania

A pair of purple martins on an Amish farm in Pennsylvania (Photo by fishhawk on Flickr, Creative Commons license)

While these cavity nesters have adopted apartment and gourd nesting in the East, their ancestral nest sites were abandoned woodpecker holes in dead snags. Yet, by 1900, the eastern purple martins had converted almost entirely to human-made houses.

Purple martins are the largest swallows in North America. The males are entirely purple but appear black in the field while female purple martins are pale below with a pale collar and forehead. They arrive in northwestern Pennsylvania from their winter homes in Amazonia Brazil near Manaus in late April, according to studies by Dr. Bridget Stutchbury and her students. By putting geolocators on five purple martins, those researchers found that it took the birds on average 23 days at 180 miles a day including a nonstop Gulf of Mexico crossing to reach northwestern Pennsylvania. However, one martin made it in 13 days which meant that it flew 300 miles a day.

Male purple martins arrive first and try to claim as many compartments in a birdhouse as possible and sometimes multiple gourds too. If each porch in a birdhouse is divided by a barrier that prevents a male seeing into the adjacent apartments, a single male defends less territory. This enables more martins to occupy a house.

A pair of purple martins, the male on the right

A pair of purple martins, the male on the right (Photo by Andrew Reding on Flickr, Creative Commons license)

To attract a female to his nest, a male flies from his nest cavity, sailing in a wide arc, and then returns to his nest site, ending in a steep dive. As he lands, he enters his nest, turns around, pokes his head out and sings. A female, more interested in evaluating the nest cavity instead of the male, visits it repeatedly over several hours. Finally, he treats her as his mate and starts accompanying her (mate-guarding) when she leaves the nest site. After several days they move in together and greet each other whenever they are separated.

Purple martins have a wide variety of calls and songs, but the male uses a series of clicks called the “croak song” and the female a “chortle song” during courtship. Most famous is the very loud “dawn song,” which is used before daylight perhaps to attract other martins to the bird house.

Studies of nest preferences for purple martins indicate that they like the higher compartments in bird houses and the deeper they are, the more fledglings they can produce. Best of all are the gourds that are so deep that the martins can raise seven young in them instead of the more usual four in the birdhouse compartments.

Nest-building in Pennsylvania begins in early to mid-May and is mostly done by the female purple martin, although the male may collect green leaves and sometimes starts nest-building by gathering a few twigs or leaves. But once the female begins, he either accompanies her while she gathers nesting material or sits near the nest cavity and watches.

A purple martin nest with eggs

A purple martin nest with eggs (Photo by OakleyOriginals on Flickr, Creative Commons license)

She builds her nest out of twigs, stems of herbaceous plants, leaves, and mud, but each pair designs their own nest so they vary widely in shape. The depressed nest bowl is filled up with green leaves that often hide the three to seven white eggs the female lays. In Pennsylvania, returning martins reuse the same nest cavities and fledge more young than those that use clean compartments.

The female has a brood patch and is thought to be the incubator during the 15 to 18 days of incubation, but the male often relieves the female for long periods and sits on the eggs.

Purple martin fledglings

Purple martin fledglings (Photo by OakleyOriginals on Flickr, Creative Commons license)

The altricial young hatch and are brooded by the female until their eyes open in 10 days. Both parents feed the nestlings and when they are 12 days old, they cluster together near the entrance hole to greet their parents. By the time they are 17 to 21 days of age, they have their feathers and are exercising their wings by stretching and flapping. Finally, they fledge when they are 28 to 29 days old. In northwestern Pennsylvania that is mid-July on average.

Their parents continue to feed them for several days, but the young begin catching insects on their own and are fully independent seven to 10 days after they fledge. Then they join other fledglings in roosts.

James Hill at the Purple Martin Conservation Association in Edinboro, PA

James Hill at the Purple Martin Conservation Association in Edinboro, PA (Photo by Bruce Bonta)

Back in 1990, my husband Bruce and I visited James Hill, who had founded the membership and research-based Purple Martin Conservation Association in Edinboro, Pennsylvania. Already, Hill had set up a variety of nesting apartments and assemblages of gourds to figure out the kinds of nests purple martins preferred. He also published an excellent quarterly periodical called Purple Martin Update, which is still being published.

Today the PMCA is housed at the Tom Ridge Environmental Center under the leadership of Joe Siegrist. In late summer he takes people on pontoon boat tours near sunset to view the huge martin roost of 20,000 at Presque isle Bay, which draws in birds from at least a 250-mile radius. Under their program called Project Martin Roost they’ve discovered at least 350 premigratory roosts in eastern North America and Canada. Most of these roosts are so large they show up on weather radar.

Usually the roosts are over large bodies of water with cover from reed beds and long brushy islands, but in urban and suburban settings they roost in trees or on manmade structures such as bridges and pipes. The farther south these roosts are, the longer the martins remain. Some are used from eight to 12 weeks.

A purple martin flying at the Codorus State Park in Pennsylvania

A purple martin flying at the Codorus State Park in Pennsylvania (Photo by Henry T. McLin on Flickr, Creative Commons license)

But Stutchbury’s geolocator studies show that once the Pennsylvania birds set out for the south, they fly almost nonstop until they reach Central America as soon as five days later. Then they rest before continuing on to Brazil more slowly than when they head north in the spring.

Other research projects the PMCA engages in with citizen scientists are a Scout-
Arrival Study that tracks the northward migration of the first martins to be sighted at individual colonies and Project Martin Watch, a continent-wide effort to study the nesting dates, number of eggs laid and hatched and how many nestlings survived. They’ve also been banding martins since 1987.

Wet weather is the largest threat to purple martins. If there is a long, cold, rainy spell in June and July, most of the year’s progeny will perish of cold, drown in their nests, or die of starvation since martins don’t fly in wet weather. European starlings and house sparrows may take over martin nests, so martins depend on their human landlords to remove the non-native invaders.

Owls and snakes are also a threat and deeper cavities make nests harder for owls and other avian predators to reach into. Snake guards installed on birdhouse poles can keep them away from the birdhouses.

With enough folks willing to be purple martin landlords, the eastern population of this beautiful bird should grow and thrive.