The Masked Bandit

It is late afternoon on May Day, and the masked bandit is standing on the stoop of our veranda door. He looks around alertly as I speak to him.

“What are you doing here?” I ask.

Common yellowthroat male

Common yellowthroat male (Photo by DanPancamo on Flickr, Creative Commons license)

He doesn’t seem inclined to move or to answer. After all, he’s only a songbird who sings “witchedy, witchedy,” and he doesn’t even honor me with his song.

Instead, he flies up along the edge of the house as if he is looking for insects. Then he lands in front of the living room window, and I wonder if he has seen his reflection in the glass. Or had he previously noticed his reflection in the storm door and wished to fight his rival.

He flies back to that door and looks as if he wants to go inside. Finally, he flies up to the transom above the door and pecks at his reflection. Apparently, he does see a rival in his reflection, but he is not as persistent as towhees and cardinals, both of which have tapped for hours and many weeks on our windows.

Common yellowthroat male singing

Common yellowthroat male singing (Photo by Andy Morffew on Flickr, Creative Commons license)

After a few minutes, he flies back down to the stoop and then suddenly silently flies away. That is the last we see of him around our home, although we hear plenty from him and other common yellowthroats throughout the breeding season. Still, I am left with more questions than answers about his visit and readily admit that despite watching birds for most of my life, I am still puzzled by much of their behavior.

The name of this warbler “common” describes its ubiquitous presence during the nesting season in most of North America from every province in Canada to western Mexico, and its position as the number one or possibly two most common breeding warbler in Pennsylvania. Its “yellowthroat” refers to its bright yellow throat, chin and breast.

A female common yellowthroat

A female common yellowthroat (Photo by D. Gordon E. Robertson in Wikimedia, Creative Commons license)

But I prefer my name for the male common yellowthroat, the “masked bandit” because of his distinctive black mask outlined above in white which separates his black forehead and mask from his olive head, back, and wings. The female is plain olive with a pale yellow chin, throat, and breast, ideal for blending into the shrubby habitat where she builds her nest and cares for her young.

Ornithologists have distinguished 15 subspecies of common yellowthroats based mostly on slight variations in their color, size, wing and tail proportions. Our common yellowthroat Geothlypis trichas trichas, once split into the northern and Maryland yellowthroats, has now been combined and ranges from Newfoundland west through Ontario and Minnesota, south to east Texas and east to the Appalachians and includes the rest of eastern United States and Canada, but excludes the coastal Carolinas and most of Georgia and Alabama (subspecies typhicola) and Florida (ignota).

First collected in Maryland, the common yellowthroat was one of the first birds described from the New World by the pioneering Swedish taxonomist Carl Linnaeus back in 1766. He named it Geothlypis meaning “a kind of finch of the earth” and trichas meaning “a thrush,” because European warblers hadn’t been classified at that time. Even later, taxonomists discovered that European warblers are not related to New World warblers, hence the designation of our warblers as “wood warblers.”

A common yellowthroat in Chester County, Pennsylvania

A common yellowthroat in Chester County, Pennsylvania (Photo by Kelly Colgan Azar on Flickr, Creative Commons license)

Not all New World warblers favor woods including the common yellowthroat. It prefers dry or wet shrubby growth in weedy fields and marshes on both their breeding and wintering grounds. Since we have a weedy wetland and an upland dry weedy field, our land supports several breeding yellowthroats. I suspect our veranda visitor was claiming the overgrown beginnings of our stream as his territory.

Male common yellowthroats arrive in our area a week ahead of the females, usually in late April or early May and vigorously defend their territory from encroaching males, although real fighting with each other increases with the arrival of females.

The females signal they are ready for breeding by fluttering their wings and tail and chipping quickly. Once they pair up, males follow their mates closely, probably hoping to prevent the sometimes polyandrous females from copulating with other males.

A common yellowthroat nest

A common yellowthroat nest (Photo by Kent McFarland on Flickr, Creative Commons license)

Nest building by females begins almost immediately after they choose a site on or near the heavily vegetated ground, and their nests are supported by sedges and grasses, cattails, briars or reeds. Finding their nests is difficult because they are well concealed. In addition, both males and females are extremely secretive, sneaking through the underbrush on pathways hidden by thick vegetation when a human approaches a female sitting on her nest or later, after the eggs hatch, when they are feeding nestlings.

Females lay on average four white eggs spotted or blotched gray, reddish-brown, lilac, or black. They incubate the eggs 12 days, and their nestlings are totally helpless when they hatch. But they grow amazingly fast and while they are able to fledge at eight days by climbing over the edge of their nests and moving into heavy vegetation, most wait until they are 12 days old to fledge.

A male common yellowthroat preparing to feed its nestlings

A male common yellowthroat preparing to feed its nestlings (Photo by U.S. Fish and Wildlife Services on Flickr, Creative Commons license)

Both parents have been feeding them and continue to do so for three weeks while the fledglings strengthen their wings and move into nearby woods or thickets. In Pennsylvania common yellowthroats are forest edge species and nest building begins here the first week in May. The Second Atlas of Breeding Birds in Pennsylvania observers reported seeing young through July which suggests that they may have two broods.

Common yellowthroats are wholly insectivorous, eating beetles, grubs, the larvae and adults of moths and butterflies, flies, ants, spiders, plant lice, leaf hoppers and leaf rollers, gleaning food for themselves and their young from the ground or shrubbery. As long ago as 1907, E.H. Forbush in Massachusetts watched a male common yellowthroat eat 52 gypsy moth larvae before flying away and concluded that the yellowthroat was an efficient enemy of the pest. He also saw a yellowthroat eat 89 aphids in a minute. Another researcher found that yellowthroats consumed large numbers of cankerworms in orchards.

Both eggs and nestlings are preyed on probably by snakes, mice, chipmunks, skunks, opossums, and raccoons and adults are occasionally caught by loggerhead shrikes, merlins, American kestrels and northern harriers.

A common yellowthroat female feeding a brown-headed cowbird fledgling

A common yellowthroat female feeding a brown-headed cowbird fledgling (Photo by Bill Thompson/USFWS on Flickr, Creative Commons license)

But the parasitizing of their nests by brown-headed cowbirds may be the greatest threat to yellowthroats. One study, of 20 nests with cowbird eggs, found that only three produced young yellowthroats. On the other hand, some yellowthroats seem to recognize cowbird eggs or notice that their own eggs have been removed and replaced by those of cowbirds, and they build a second nest or even a third one on top of the parasitized nest.

By the third week of August some common yellowthroats in Pennsylvania start their migration south, although the peak is during the second and third weeks of September. Flying through the night, adults and immature birds head for the Caribbean islands or Central America all the way to Panama, seeking the same shrubby vegetation to spend the winter. However, at least those wintering in Quintana Roo, Mexico, are segregated by sex with males preferring second-growth scrub and natural open habitat and the females more common in open pastures and fields according to a 1990 study by A.L. Ornat and R. Greenberg.

Like many songbirds, even those as numerous as the common yellowthroat, there have been no long-term studies of their breeding biology or behavior, but recently there has been interest in their song and singing behavior. Even though I’ve heard only their “witchedy, witchedy” song and scolding notes, it turns out that their song varies in the number of notes per phrase, enough that their mates can distinguish them from other males.

A juvenile male common yellowthroat, which learns its calls by listening to adult males

A juvenile male common yellowthroat, which learns its calls by listening to adult males (Photo by DickDaniels on Wikimedia, Creative Commons license)

Male nestlings learn their song by listening to adult male yellowthroats, but, in some cases, both in captivity and in the wild, they learn other songs as well. One wild yellowthroat in Massachusetts sang his own song in addition to a perfect rendition of a chestnut-sided warbler’s song. And a captive yellowthroat learned a yellow warbler’s song.

Thinking back to the many male common yellowthroats I’ve encountered over the years, including our veranda visitor, I must agree with Alfred Otto Gross’s description of the birds he spent hours watching from a blind decades ago. …”one is impressed with the vigorous personality of the male. He nervously raises his alarm with a variety of scolding, interrogative chirps and chattering notes and his dark inquisitive eyes sparkle with excitement through the black masks.”

 

Vulture Days

Turkey vulture in flight over Brush Mountain

Turkey vulture in flight over Brush Mountain

Last September once again I missed International Vulture Awareness Day. That was on September 7 and my husband Bruce and I were celebrating our fiftieth wedding anniversary in the province of Quebec. Specifically, we were sitting six feet away from the largest common gannet colony in the Western hemisphere, watching them fighting, mating, tending young, and diving for food.

If only watching turkey vulture behavior on our mountain was as easy. Of course, I do see them sailing up and down Sapsucker Ridge most days from early March, when they return from their winter quarters, until mid-November when they are off again. We think we may have had a pair nesting somewhere on the talus slope because several years ago our son Dave saw an almost grown youngster sitting on the rocks.

Then, in the spring of 2012, our caretaker Paula Scott reported seeing a turkey vulture sitting the entire day on top of the deserted and wrecked home our late former neighbor Margaret McHugh. Paula watched the bird from her own home that had been built farther up the hill and looks down at the old place.

According to researchers, old, deserted homes and other buildings are favorite nesting places for turkey vultures. I was hopeful that I would finally be able to watch from Paula’s home (a natural blind) the domestic affairs of a pair of turkey vultures.

But it was not to be. Paula never saw any further sign of vultures near the house, and it was too dilapidated for us to climb up to the attic and check it out. Probably the close proximity of the Scotts’ home had discouraged the vultures if, indeed, they had been interested in nesting in the old house.

Maybe they nested in the talus slope instead or in the crevice of one of many fallen trees on our property. I only know that on September 24, a clear, breezy day, I was walking down First Field when I spotted a vulture sitting on a power pole at the base of Sapsucker Ridge. At first I thought it was a black vulture because it had a gray head. But so do immature turkey vultures and this one had a long tail, not the short one of a black vulture. Then a mature turkey vulture followed by a second and a third one soared close to the power pole vulture as if showing the youngster how to ride the wind as they do.

Juvenile turkey vulture grooming itself at the edge of a talus slope

Juvenile turkey vulture grooming itself at the edge of a talus slope

But the youngster paid no attention to the soaring vultures. Instead, it groomed itself. It also ignored me as I edged closer and closer. Even when I walked beneath the pole, shouted and clapped my hands, it didn’t budge. It didn’t even look down at me. Only an immature would be so oblivious to a human. I studied it for a long time, but it never did fly off. However, watching it had given me the chance to celebrate International Vulture Awareness Day a little late.

Even though our turkey vultures are the most widely distributed and abundant of all vulture species worldwide, ranging from southern Canada to the southern tip of South America and on large and small islands from Cuba and Puerto Rico to the sub-Antarctic Falkland Islands, many species have rapidly dwindling populations. For instance, three of south Asia’s vulture species lost 99 percent of their population in 25 years due to a veterinarian drug used on livestock that is toxic to vultures and five African species are gravely threatened by accidental and purposeful poisoning. Since most people don’t like vultures, they only learn after they lose them how invaluable they are in cleaning up dead creatures.

Hawk Mountain Sanctuary researchers have been studying turkey vulture migration behavior since the spring of 2003 by radio-tagging some and surgically implanting a data logger in the bodies of others which records core body temperature and heart rate. They also wing-tagged dozens of them in an effort to learn more about the extent, causes and consequences of their annual migration.

According to their website, their goals in monitoring New World raptors are to “routinely monitor seasonal populations of New World vultures in North, Central and South America, prevent catastrophic population declines by sharing learned information with conservation partners, and use black and turkey vultures as environmental sentinels of ecological change and environmental contamination, including climate change and heavy metal contamination..”

They have discovered that our subspecies of turkey vulture Cathartes aura septentrionalis is a partial migrant to as far south as Texas and southern Florida, although in February of 2010 Dr. Keith L. Bildstein and Lauriane Streit drove down the Delmarva Peninsula from Milford, Delaware to the Chesapeake Bay Bridge tunnel toll booth passing numerous chicken farms, each with its own flock of vultures, and called it “one of the biggest East Coast winter resorts for vultures.”

A longer drive along the coast found that there were more turkey vultures than black vultures, for example, on the Delmarva drive they counted 245 turkey vultures to 23 black vultures. But on counts in the Appalachian Mountain from northern West Virginia to North Carolina and Tennessee there were more black vultures than turkey vultures.

Juvenile turkey vulture cleaning its beak on a rock

Cleaning its beak (?) on the rock

Bildstein wrote the turkey vulture section in the Second Atlas of Breeding Birds in Pennsylvania and reflects on the difficulty of finding turkey vulture nests, saying that up to 70 percent of a local population may not breed. Nevertheless, he has good news about their numbers. They have expanded in the Appalachian Plateau region of Pennsylvania from their former range in the more southerly part of the state and have shown a 13 percent increase in breeding blocks from those reported in the first Pennsylvania breeding bird atlas project back in 1983-89. The Breeding Bird Survey also reported a 50 percent increase in turkey vultures between 1966 and 2009. Migration hawk watches throughout the state similarly have observed an increase in turkey vulture migrants.

Bildstein believes that the increase is due to several factors: the increasing numbers of wildlife including white-tailed deer that are killed on highways and decreased persecution of them by humans. While most Pennsylvanians may not care that much for turkey vultures, apparently they appreciate their role as nature’s scavengers, cleaning up not only dead wild animals but domestic ones as well.

Using their keen sense of smell to help locate food, they feed on carrion without getting much gore on their naked heads. No doubt, this reduces their exposure to bacteria, parasites, and disease. Still, in his “Vulture Chronicles,” an absolutely delightful ongoing account on the Hawk Mountain Sanctuary website by Bildstein and other researchers of their work with vultures, not only in the Western Hemisphere but in the Eastern one as well, he writes that they still are threatened by “high levels of toxic chemicals in human habitations (including human drugs in urban areas, and agricultural pesticides in farmlands)…” In addition, they often fly into transmission lines while searching for carrion with their heads pointed down. They may also crash into vehicles. Because they feast on dead and dying birds and human garage they are exposed to “veterinarian drugs and antibiotics that contaminate the carcasses of domestic livestock and heavy metals that contaminate our dumping grounds.” Those that feed on such food Bildstein calls “human-subsidized” vultures and cites several incidences in North and South America of turkey vultures zeroing in on humans at campgrounds and other places where they might get human leftover food.

That brings me to a poem by Hilaire Belloc written in 1897 for his book More Beasts for Worse Children which says:

The Vulture eats between his meals,
And that’s the reason why
He very, very, rarely feels
As well as you and I.

His eye is dull, his head is bald,
His neck is growing thinner.
Oh! What a lesson for us all
To only eat at dinner!!

Juvenile turkey vulture getting ready to head up into the roost tree

Getting ready to head up into the roost tree


All photos by Dave Bonta.

Eastern Wood-Pewees

Eastern Wood-pewee by Kelly Colgan Azar

Eastern Wood-pewee by Kelly Colgan Azar
(Creative Commons BY-ND license)

During warm August days most songbirds are quiet. They are molting and stay hidden from potential enemies. But the eastern wood-pewee drawls his plaintive “pee-ah-wee” song. He, it turns out, doesn’t molt until after he migrates. Without his songs, our August forest would be almost silent.

Even late in the month, eastern wood-pewees call from all directions, not only a clearer, crisper “pee-a-wee” but also a more urgent “wee-oo” over and over. Perhaps because this bird is more easily heard than seen and its private life even more difficult to observe, most studies of eastern wood-pewees emphasize their songs and calls.

Early ornithologists had a variety of opinions regarding the male’s song. Dr. Elliot Cowes wrote that “its presence is soon made known by its oft-repeated melancholy notes…” F. Schuyler Mathews in his Fieldbook of Wild Birds and Their Music stated that “there is no bird which compares with the Wood Pewee in sheer laziness of style; he does not attempt to ‘hit’ a note squarely, he reaches for it with all the sentimentality… of the inexperienced and uncultivated singer, capturing us in spite of his error by the perfect sweetness of his voice.” Mathews then summed up the pewee’s song as “always the same, slow, peaceful, restful and thoroughly musical.” Bradford Torrey called the song an “elegy.”

Writing in Arthur Cleveland Bent’s Life Histories of North American Flycatchers, Larks, Swallows, and Their Allies, Winsor Marrett Tyler described the eastern wood-pewee’s song as “a sweet, pure, tranquil whistle delivered calmly in short, slow phrases. The leisurely notes, sliding smoothly and evenly as they change in pitch, give the impression of restfulness and peace, almost of sadness.”

However, it is in the predawn and evening that the eastern wood-pewee’s song takes on more complexity as Donald Kroodsma proved in his ground-breaking The Singing Life of Birds. Having read numerous descriptions of these songs, he was in place with his recording equipment near a large silver maple tree, which he knew was a song perch for a pewee, an hour before sunrise.

Already the bird was tuning up a series of “pee-ah-wee” songs followed by a single “wee-oo.” Then he twittered overhead, announcing he had arrived and was ready for his predawn concert. He uttered a single “pee-ah-wee,” then an “ah-di-dee” and in a frenzy of singing he delivered 10 songs in 20 seconds, at the rate of one every two seconds or 30 a minute.

Eastern Wood-Pewee singing by Andy Reago & Chrissy McClarren

Eastern Wood-Pewee singing by Andy Reago & Chrissy
McClarren (Creative Commons BY license)

“Already he teaches me one of his combination songs, “wee-ooo-di-dee,” Kroodsma wrote. “Most of these are followed by ‘ah-di-dee.’

“I find the pewee irresistible,” he continued. “After 25 minutes, at 4:50 a.m., 22 minutes before sunrise, he ends as he began: pee-ah-wee…wee-ooo-di-dee…ah-di-dee…pee-ah-wee…in rapid fire, then a twitter and off he flies…”

Unlike many birds, the pewee’s virtuoso performance has been programmed in his genes and thus he does not have to learn his songs from an adult. For that reason, eastern wood-pewees have no regional learned dialects so their songs remain the same throughout their breeding range of central and eastern North America as far north as the Maritime Provinces of Canada, west to southern Manitoba, and south to northern Florida and southeast Texas.

The eastern wood-pewee (Contopus virens) is a dull-colored flycatcher that looks almost exactly like its sibling species the western wood-pewee (Contopus sordidulus). Only its unique song distinguishes it from the harsh, buzzy “peer” of the western wood-pewee.

Here in the eastern United States, the eastern wood-pewee is most closely related to the larger olive-sided flycatcher (Contopus borealis), but it also resembles the smaller Empidonax flycatchers, most notably the least and Acadian flycatchers, as well as the eastern phoebe (Sayornis phoebe). However, the eastern wood-pewee does not flick its tail like a phoebe. It is also larger than the least and Acadian flycatchers, lacks their white eyerings, and possesses longer and more pointed wings. But it has a triangular-shaped head, unlike the other flycatchers. Otherwise, its back, head and wings are dark, grayish olive, and it has pale wingbars, whitish or pale yellow underparts, a dull white throat, and a bill with a black upper mandible and a dull orange lower mandible.

Like all flycatchers, it sits upright on a branch in the middle canopy, sallies forth after flying insects, snaps one up, and returns to its perch. In our woods, the great crested flycatcher uses a higher perch than the eastern wood-pewee while the Acadian flycatcher and then the least flycatcher are perched below the pewee.

Eastern Wood-Pewee with Nestlings by Andy Reago & Chrissy McClarren

Eastern Wood-Pewee with Nestlings by Andy Reago & Chrissy
McClarren (Creative Commons BY license)

Of course, it would be rare to find all of them hawking insects in the same vicinity, even though the eastern wood-pewee seems to be a generalist as far as habitat is concerned, using both edge and suburban habitats, open, wooded riparian and/or drier areas, eastern deciduous forest, orchards, open pine woodlands in the South, and mixed hardwood-conifer northern forest.

In Pennsylvania we “have a high proportion of the species’ North American population,” according to the Second Atlas of Breeding Birds in Pennsylvania. The eastern wood-pewee was found in 88% of the breeding blocks but was “absent from some higher elevation blocks in densely forested northern mountains” and also largely ‘absent from the large and treeless expanses in the Piedmont Province” and tends to avoid our areas of coniferous forest. Altogether, though, ornithologists estimate that we have 315,000 singing males during the breeding season.

Eastern wood-pewees are one of the latest migrants to arrive here, probably in part because they spend their winters in South America from northwestern Colombia and northeastern Venezuela to southern Peru, northern Bolivia and Amazonian Brazil. Whether they are day or night time migrants is still debatable, but Mike Lanzone, who has been studying the songs of nocturnal migrants, says that they are mainly nocturnal.

“Evidence is very strong simply from the fact that they show up in good numbers at dawn where they were not the day before. [Also] I have heard them predawn with other nocturnal migrants, not singing but making their tanager-like “chip” call,” Lanzone says. Other researchers have found that they are killed at television towers at night.

Usually, I hear the first eastern wood-pewee the first week in May and by the second week, when I am participating in the North American Migration Count, I record as many as five singing males on our property. Apparently, they need territories anywhere from five and a half acres to 19 acres in size, which they defend by chasing off at least 17 songbird species while singing. They also may change their singing patterns by not singing when other species or their own are singing. On the other hand, they don’t mind sharing their territories with least and great crested flycatchers.

Three Little Pewees by muscogeegirl

Three Little Pewees by muscogeegirl
(Creative Commons BY-NC-SA license)

Males do chase females and feed them during courtship, but so far there has been no detailed description of courtship or mating. Roy Ickes, writing in the Atlas of Breeding Birds in Pennsylvania, reported that the first nest-building was recorded on May 20, with parents carrying food for their young from June 3 until September 4.

Back on August 28, 2011, I watched an eastern wood-pewee feeding two hollering fledglings on a tree branch.

Nest-building is thought to last several days and the nests themselves are perched on a horizontal branch of a tree anywhere from 16 to 68 feet from the ground. A small nest that looks like a knot on the branch, it is cup-shaped, woven of grasses, and covered on the outside with lichens. Other materials such as weeds, wool, twigs, roots, leaves, pine needles and bark strips have also been used in its construction. Nest trees include 28 deciduous tree species and six conifers, although one study from Canada indicated a high preference (45%) for oak tree species, particularly white oaks. And Dr. Samuel Dickey, writing mostly from Pennsylvania to Arthur Cleveland Bent, found eastern wood-pewee nests in white, red, and black oaks, sugar maple, black walnut, yellow locust, elm, apple, and pear, “generally in specimens of large growth.”

The female lays 2 to 4 white eggs speckled with brown to purple on the large end on consecutive days, and she alone has a brood patch. The male feeds her while she incubates the eggs and may watch the nest when she leaves it. On average it takes 12 days before the altricial young hatch, but Samuel Dickey reported that the incubation period of the six nests he watched was 13 days.

Even though observers in Pennsylvania mentioned seeing parents carrying food to nestlings as late as September 4, at least some eastern wood-pewees are on their solitary way south as early as the last week in August and as late as the second week in October. I’ve heard them singing here as late as September 12, but these are birds that even sing on their wintering grounds.

Breeding Bird Survey data from 1966 to 2009 showed a 1.7% overall population decline per year, mostly in the central United States. But here in Pennsylvania there was in increase in population. I can only hope that their numbers will remain high and that I will continue to hear their drawn-out laments on hot August days.

Eastern Wood Pewee fledgling by muscogeegirl

Eastern Wood Pewee fledgling by muscogeegirl
(Creative Commons BY-NC-SA license)