Category Archives: Plummer’s Hollow

Sonogram image adapted from the Royal BC Museum.

The blue-headed vireo chants endless variations on a few, key ideas. The bird guides all speak of a kind of deliberation – one could just as well say thoughtfulness – in his delivery of short, robin-like phrases designed to carry a couple hundred yards through deep forest. His repertoire includes no more than twenty distinct phrases, but he seldom repeats a given sequence. Whether you choose to call this improvisation or shuffle play says more about you than it does about the vireo, who doesn’t care whether you view him as an artist or a machine.

The variations aren’t random, though: he consistently prefers some phrases to others. Some are drawn from a shared stock of blue-headed vireo folk material, so to speak, which varies from region to region. But each bird also has a few phrases that are unique to him. This vireo calling from a witch hazel branch on the first of May in a maturing chestnut oak-heath understory forest in central Pennsylvania sings a song never before heard in the three and a half billion years of life on earth. When he dies, it will die with him. Listen well.

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“Some males sing slowly when foraging between incubation bouts… Near nest with eggs, song often reduced to repetition of only 1-2 phrases,” says the most authoritative source (Ross D. James, “Blue-Headed Vireo,” in A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, Cornell Laboratory of Ornithology and the Academy of Natural Sciences, No. 379 [1998]). This one chants four phrases, fixes his beady eye on me, then hops right into a beautiful little nest suspended from the branch of a mountain laurel bush some six and a half feet off the ground. It’s about the size of a teacup, the outer layer woven from what appear to be short pieces of bark from wild grapevine; dead leaves; white paper, presumably from some scrap of wind-blown litter; and gray paper from a hornet nest – probably that one over near the edge of the field that blew out of its tree during the high winds of March. Finer material used in the lining – dry grasses, rootlets, fungal mycelia and the like – protrudes slightly above the rim of the cup.

Like many nest builders, vireos are gifted at improvising with materials at hand. Spider web or the silk from last year’s caterpillars supplies the mortar that holds the whole construction together and fixes it to the branch. We tend to forget just how much silk persists in field and forest over winter. Several times this past winter and early spring I’ve been out when low sun was at just the right angle and was amazed by how many gleaming strands of gossamer still stretched between twigs and along the ground, even after the snow had melted.

These vireos have only been back from their winter sojourn in Central America or the Caribbean for three weeks, at most. They’ve wasted no time in pairing off, setting up house and, from all appearances, laying eggs and beginning to incubate. Like many neotropical migrant songbird species, they raise a single brood each season, though their early return gives them enough time to try re-nesting if a predator wipes out their first clutch. This is much more the exception than the rule, however, especially for the northern subspecies Vireo solitarius solitarius, which migrates the farthest.

And there are plenty of predators: crows, snakes, raccoons, gray squirrels – even normally vegetarian white-tailed deer have been observed eating songbird nestlings. This nest seems high enough to avoid the deer, and squirrel numbers are down following a couple of harsh winters and poor acorn crops. Then, too, the blue-headed vireo often nests “near small openings or edges of wetlands and lakes,” says Ross D. James, so it may have evolved more defenses toward edge-dwelling predators than other forest-interior specialists such as wood thrushes and scarlet tanagers, whose numbers are in decline throughout their range.

But the blue-headed vireo, too, likes large tracts of mostly unbroken, mature forest. This makes sense, because it’s the environment in which most of these neotropical migrant songbirds have evolved: “areas where extensive forest predominates . . . with trees that are middle-aged to mature, with high percent canopy closure (usually >75%), and where there is some (but not dense) understory of shrubs and saplings.” The blue-headed vireo displays more flexibility in habitat selection than some of the more specialized passerines, nesting in everything from northern conifer forests to dry oak forests like ours to the mixed mesophytic forests of the southern Appalachians. But the monograph warns that “Extensive clear-cutting is detrimental. Even partial clearing may be serious…”

The recent rediscovery of the ivory-billed woodpecker suggests that some species may be more resilient than we once supposed. But the rapid regeneration of southern swamp forests that were never completely denuded of all their oldest stands of bald cypress in the first place should not allow us to become lured into a false sense of security about the long-term survival of interior-forest specialists in the east. Around here, most forests were clearcut twice in the 19th century, back in the charcoal iron era, and at least once more in the early 20th century during the chemical wood era, before the petrochemical revolution gave the woods a break (while of course accelerating the degradation of nearly all ecosystems worldwide). But the reprieve thus granted forest-dwelling species is probably over. In the last couple of decades, economic and cultural forces have pushed the frontiers of year-round human settlement farther and farther into areas that were once thinly dotted with poor farms like ours or with hunting cabins. Deep woods habitats are disappearing.

A number of morbidly fascinating things happen when once-intact forests are fragmented by roads or subdivisions. As the proportion of edge to volume increases, secure refuges from artificially numerous habitat-generalist predators and barriers to the spread of non-native invasive species dwindle and disappear. While habitat edges or ecotones are often areas of concentrated biodiversity, they are very much a double-edged sword. The Great Eastern Forest once accounted for at least ninety percent of the land cover east of the tallgrass prairie; openings were small and temporary. The loss of naturally occurring forest openings in over-managed or too-young forests cannot fail to have negative impacts on species specializing in those kinds of environments. And the establishment of unnaturally long-term or permanent edges is thought to compromise essential functions of forest ecosystems through (for example) increased light and wind levels, which conspire to degrade the depth and quality of humus for hundreds of feet in from the edge. Keep in mind that the humus layer, where the base of the food chain is concentrated, contains the keys to the whole ecosystem. Air and water pollution – also greater along edges – can wreak havoc on soil chemistry, with probably dire consequences for the delicate balance of mostly unclassified microbial life.

The ripple effects from damage to the base of the food chain can take decades to register in the loss of what conservationists call “charismatic megafauna” – the mammals, birds, and occasionally reptiles and amphibians around which conservation campaigns tend to be built. DDT is still found in the tissues of many North American songbirds, and contrary to what one might suppose, levels are highest among non-migratory species in the United States, where use of the chemical was ubiquitous up until forty years ago. Who knows what its effects on songbird reproductive success might be? Acid precipitation leaches calcium from the soil, with negative consequences for land snails – one of our most numerous and biodiverse families of forest invertebrates. Ground-foraging bird species such as wood thrushes and ovenbirds eat a lot of snails, especially when they’re laying eggs and need the calcium. An on-going study in upstate New York has found a correlation between acid precipitation and nest failure among wood thrushes. Acid precipation is most severe and its effects most deleterious in ridgetop forests with unbuffered soils – which describes well over half of the intact forests in central Pennsylvania. And snails are also among the forest litter-dwelling organisms most likely to impacted by edge effects.

Some birds and mammals are highly adaptable to sudden change; many other organisms are not. The effects of habitat fragmentation can take a while to show up, because local and regional population collapses as a consequence of inbreeding depression don’t happen overnight. And how much time has to go by before anyone even notices and documents the change? The vast majority of scientific studies go on only as long as it takes a graduate student to earn a degree; institutional support is rarely forthcoming for the kind of long-range studies needed to compile comprehensive life histories of single species, let alone to disentangle ecosystem functions – a matter of guesswork for virtually every natural ecosystem on the planet. My mother recently told me about an expert on chickadees who once said that if she had halted her study after only two years, she would have ended up with different and in some cases directly opposite conclusions from those she arrived at after several decades of field observations and experiments.

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This kind of conservation message may seem a bit removed from the ordinary fodder here at Via Negativa, but it’s very close to my core motivation in launching this blog a year and a half ago. More than once I’ve quoted the ecologist’s mantra, attributed to Frank Engler: “Nature is not only more complex than we know, it’s more complex than we can know.” Knowing that we don’t know has always struck me as an extremely valuable insight, central to ancient and indigenous belief systems the world over. Shouldn’t the recognition of existential ignorance foster humility and reverence toward the objects of our unknowing? Indeed, as the epigraph from Rene Char says, “How can we live without the unknown before us?”

But as I said the other week in my post about the black snake, the most important mysteries are those that lurk within the scrim of the allegedly ordinary, the unique and unrepeatable details of particular beings and events. Hence the poetry, the ruminations, the daily cartoon, the attempts at fiction and photography; hence my fascination with the scatological and the bizarre. I refuse to leave anything out.

Now the digital camera gives me one more way to pile up evidence for what is, to me, a self-evident truth. This camera isn’t very good at close-ups or depth of field. A still photo tells you little about context and motion and nothing at all about sound or odor. The wind rocked the branch; a ten-second rain shower pattered down. When the sun came out, the vireo’s white-ringed black eye seemed more beady than ever as his head stretched and swiveled in all directions. I walked slowly within flash range, then even closer, snapping away. He never left the nest. Hours later, when I returned with my mother, we stopped short some fifteen feet away, concerned that our scent trail could lead predators to the nest.

We felt privileged to have seen this much, the male bird having seemingly showed me his nest for reasons that are difficult to imagine. The Birds of North America monograph claims that the species is “very sensitive to close human attention at time of pairing and early nest-building; female readily abandons nest and even [her] mate. However, may nest in or near campground with unobservant traffic. Much more tolerant once eggs are laid. Sensitive again when large young are in nest…” “Tolerant” hardly begins to describe that male’s behavior. Mom says a hooded warbler did the same thing to her last year, in another part of the property: sang until she noticed him, then hopped into his nearby nest.

I tied a few ribbons of surveyor’s tape on the way back to the old woods road we use for a walking trail, one of several such – relics from the original clearcutting of the mountain circa 1815. I’ll leave it to the resident naturalist’s discretion whether and how often she wants to revisit this nest. For my part, I’ve seen enough. If before I was still a bit fuzzy on the difference between the blue-headed and red-eyed vireo songs, now I wonder how I ever could have confused them. Minimal as it may be, the importance of this kind of knowledge should not be underestimated: it’s what makes us feel at home in a place, knowing the names of our neighbors and some of their habits.

Later in the afternoon I sat out on my porch for a few minutes and listened to another blue-headed vireo singing up in the woods, probably defending the next territory down from the one that I’d watched. Maybe by the end of the summer I’ll learn to tell them apart, these two singers. And maybe I’ll learn something from the effort. A few ideas, endlessly repeated in endlessly novel ways: it’s no more or less than what I’ve always strived for in my own attempts to tell the world what’s what.

Cold, gray days make me think cold, gray thoughts. Years from now anyone will be able to tell just from reading this record of my internal weather what the earth and sky were doing outside my window at the time.

But the conditions are just right for the woodcock’s annual sky dance, as Aldo Leopold once termed it. Sunday evening after supper, around 6:30 p.m., I heard the distinctive peent peent call of a male woodcock in full courtship mode. He was about a week later than last year, but then, everything’s late this year. I called my parents, and they joined me out behind the barn to watch the show.

The American woodcock – also known as timberdoodle, bog sucker, night partridge, Labrador twister, or (in Quebec) la Becasse – is an exceedingly strange bird: basically a displaced shorebird that lives on earthworms and nests in old fields and young, brushy woods. Picture a fat bird about six inches long from top of head to tip of stubby tail, with a wingspan of maybe fifteen inches. Its eyes are set way back on its head, opposite its most distinctive feature – the four-inch-long bill. (I happen to have a taxidermist’s mount of a woodcock on my wall, whence the above picture.)

Phylogenetically speaking, Scolopax minor is a sandpiper; Arthur Cleveland Bent included it in his classic Life Histories of North American Shorebirds (Dover Publications, 1962 [1927]). Though Bent’s meticulous collation of accounts from the scientific literature have been superceded by the (still incomplete) Birds of North America series published by the American Ornithologists’ Union in cooperation with the Academy of Natural Sciences in Philadelphia, his life histories remain far more readable. About the woodcock, he writes,

This mysterious hermit of the alders, this recluse of the boggy thickets, this wood nymph of crepuscular habits is a common bird and well distributed in our Eastern States, widely known, but not intimately known. Its quiet retiring habits do not lead to human intimacy. It may live in our midst unnoticed. Its needs are modest, its habitat is circumscribed, and it clings with tenacity to its favorite haunts even when encroached upon by civilization.

A bit of moisture was in the air Sunday evening, and between the low barometric pressure and the very low cloud ceiling – only a few hundred feet over our heads – sounds traveled far. It occurred to me that such acoustic conditions might be especially favorable for the woodcock’s spring display, though the published literature focuses mainly on the light-gathering potential of the open areas favored for singing grounds. One study in New Brunswick did find that sites with less white noise are favored, but here in Plummer’s Hollow, woodcock displays have increased over the years, even as noise from the nearby highway has also increased. Highway noise was especially loud on Sunday, but that didn’t stop our woodcock from peenting for all he was worth.

Perhaps in part because of his long bill, the woodcock is a skilled ventriloquist. If you hadn’t read the literature, you’d swear that he was flying rapidly back and forth as he delivered his peent call, which sounds almost like a very brief sample of a cicada’s song repeated over and over, or a high-pitched nighthawk. You can peer around at the darkening clouds all you want without seeing him, though, because at this stage in the performance he’s still on the ground, standing or strutting about. In the dry prose of the Birds of North America monograph by D.M. Keppie and R.M. Whiting, Jr., “Male rotates on ground causing directional change in intensity of Peent.”

Bent reproduces a much more colorful account from 1894, courtesy of William Brewster (who heard paap instead of peent). It’s not clear to me how anyone manages to observe this behavior without infrared goggles, but Brewster assures us that

At each utterance of the paap the neck was slightly lengthened, the head was thrown upward and backward…, the bill was opened wide and raised in a horizontal position, the wings were jerked out from the body. All these movements were abrupt and convulsive, indicating considerable muscular effort on the part of the bird… The opening and shutting of the bill strongly suggested that of a pair of tongs. During the emission of the paap the throat swelled and its plumage was ruffled… The mouth opened to such an extent that I could look directly down the bird’s throat, which appeared large enough to admit the end of one’s forefinger. The lateral distension of the mouth was quite striking.

It used to be thought that a silent female could usually be found somewhere in the vicinity whenever a male performed like this, but more recent studies have cast doubt on that theory. Some males display every night for weeks as they migrate north, seemingly for the sheer hell of it. Perhaps they’re simply psyching themselves up for the real thing? In any case, the precise purpose of the male woodcock’s springtime display remains unknown. The close association of nests and singing grounds suggests some role in courtship, but the bird’s social behavior offers few clues to what that might be. According to Keppie and Whiting, woodcocks have “no known dominance hierarchy nor minimum individual distances.” They are

Polygynous [and form] no pair bond; males give no parental care. Males in north continue display long after most females commence laying eggs; some males display at widely separate singing grounds. [There's] no evidence of mate guarding or that male territory provides females with physical resources; [it remains] speculative that copulations occur mainly on singing ground. Some females visit at least 4 singing grounds before nesting and continue visits while incubating and with broods.

Whatever its function, the aerial part of the woodcock’s display is the most spectacular for human observers. After a minute or two the peenting abruptly stops and the timberdoodle launches himself into the air. Once aloft, he beats his wings in such a manner as to emit a high-pitched whistling or twittering sound, “produced by air passing between three attentuated outer primaries” (Keppie and Whiting). (In the photo above, these three are clumped together so that they appear as a single, thin feather at the very end of the wing.) Thus whistling like a dove on steroids, our hero ascends steeply in wide spirals. It’s usually possible to see his small and faintly ridiculous form silhouetted against the darkening sky as he careens around, though a couple times this past Sunday we watched him disappear into the clouds at the apex of his aerial dance.

That’s when he begins to sing for real, repeating a rapid-fire series of four to six melodious twittering notes, which, like the earlier peents, seem to come from all directions as he zigzags, banks and dives. The interweaving of these notes with the fluting of his wings produces an eerie effect. In less than half a minute he drops back down to the ground, so quickly he’s almost impossible to spot. It must be a tricky thing to put on a show like this without becoming owl bait; I would imagine that the flying maneuvers and the ventriloquism represent adaptations to avoid predators, but who knows? Keppie and Whiting do say that having eyes on the back of his head “may help male detect predators while recurringly Peenting at same localized site.”

We listened and watched while the woodcock went through four iterations of his song and dance routine. Each time the period devoted to peenting grew briefer; it was hard not to come away with the impression of mounting excitement as the bird got more and more into his act. The first couple of times we were able to pick out his silhouette, but during his third spiral dance my dad couldn’t see him, and by the fourth time, none of us could make him out. But he kept it up until the last little bit of daylight had drained from the sky. It wasn’t until I went back to the house that I remembered, for the first time that day, that it was the equinox.

The next morning I heard him again from my front porch, starting around 5:20. I walked up behind the house with my coffee and listened for a while, but I never did manage to spot him. He stopped after twenty minutes, just as the first song sparrows began calling. Last night at dusk we went out again, but he had shifted operations to the far side of the field – near the presumed nesting habitat at the edge of the woods – and we never did catch a glimpse. My mother persisted after Dad and I returned to our respective houses, and she told me this morning that she had been able to sneak right into the center of his singing ground. Although she never got a good look, during the silent pause at the end of one flight she caught a movement out of the corner of her eye, a darting shadow only a few feet away. She figured that must’ve been him coming in for a landing, because he didn’t resume peenting until she retreated a few dozen yards.

I say “presumed nesting habitat” because woodcocks are truly secretive birds. They nest in shallow depressions directly on the ground, often near the base of a tree, and their dead-leaf coloration makes them almost impossible to spot. One year we did find a telltale series of holes the diameter of a pencil in the mud right inside the woods near the old farm dump, and took that as pretty good evidence of a resident woodcock in the vicinity. Old fields like ours are not as common in Pennsylvania as they used to be; most have either gone back to woods or have been converted into malls and subdivisions. Not surprisingly, woodcocks are becoming increasingly scarce here, though I gather that the species as a whole is not in trouble. It can be found as far west as the 100th meridian, as far north as southern Canada, and as far south as the Gulf Coast, where it over-winters.

One way or another, it’s hard to imagine that too many people, other than hard-core birders, are outside at six-thirty on cold evenings in early spring to witness the courtship rites of woodcocks. Aldo Leopold, in a Sand County Almanac ( Oxford University Press, 1949), lamented the widespread ignorance of this spectacle on the part of his neighbors in Wisconsin:

The drama of the sky dance is enacted nightly on hundreds of farms, the owners of which sigh for entertainment, but harbor the illusion that it is to be sought in theaters. They live on the land, but not by the land.

Of course, home entertainment options have multiplied a hundred-fold since Leopold’s day. Even kids can rarely be found outdoors anymore, except for closely supervised activities such as Little League or soccer practice. Few people know and fewer care about (for example) skunk cabbages, whose sturdy spathes can actually generate enough heat to melt snow, and probably not too many folks bother to track down that frantic quacking sound off in the woods that we’ll be hearing in another week or two. Again, though, they don’t know what they’re missing: few sights can compare with a shallow pond in the forest that’s seething with horny wood frogs.

But it is through just such unheralded events as these that spring advances. Robins can stick around right on through the winter at this latitude, singing whenever they feel like it, and warm days in February can fool non-native snowdrops and crocuses into blooming. How could anyone attribute the power of augury to such conventionally pretty things? Spring in the Appalachians is a blend of the radiant and the supremely strange. Nothing quite spells its arrival for me like the mad sky dance of the timberdoodle.