Silver linings

The past two mornings I’ve awoken late, and haven’t gotten out onto the front porch until well past daylight. That’s O.K., though, because both mornings I’ve had the unparalleled pleasure of listening to a winter wren sing while I drank my coffee. It’s a liquid, seemingly endless burble — appropriate for a bird that spends most of its life as near to running water as possible. It nests in cave-like hollows under stream banks, especially under the boles or root balls of fallen trees, and probably the rotting end of the big butternut tree that came down a few years ago makes the stream below my front porch at least passingly attractive to winter wrens. (Ultimately, I expect this one to nest farther down-hollow.)

Winter wrens never used to breed here. They were, as their name suggests, winter visitors. But then in December of 1992, a big, wet snowstorm before the ground had frozen brought down over 100 trees in the deepest part of the hollow, many of them right on the banks of the stream. When we cleared the road — a multi-day task — we made the decision to let the logs lie down slope from the road, kissing off many hundreds of dollars worth of lumber. That spring, we were rewarded by our first-ever breeding winter wrens. It’s quite likely that these were the first members of their species to breed here since 1813, when the hollow was clear-cut for the first time. You need a pretty mature, unmanaged forest to get winter wrens. Our elderly neighbor Margaret McHugh, who died in 1991, mentioned at one point, ten years or so after the gypsy moth invasion of 1980-81, that the woods in the hollow was beginning to look awfully messy to her. “I don’t remember ever seeing this many logs on the ground,” she said — with great disapproval, of course. To most people, a dead tree is a wasted tree if it isn’t being put to some human use.

My father told the story of the winter wren at a big, statewide gathering of landowners enrolled in the Forest Stewardship Program that we hosted in the late 90s. “How do you put a price tag on the song of a winter wren?” he asked rhetorically, to great effect. Many of the other landowners shared our biocentric values, and were thrilled at this ready-made parable. But some of the foresters in attendance were clearly bothered. “What if you only harvested some of the logs? How many dead trees do these birds really need?” one of them asked. Well we did harvest some of the trees — the ones upslope from the road.

The return of the winter wren is just one of a number of positive changes here since I was a kid, and I thought it only fair that I highlight a few others after yesterday’s gloomy post. I spent today trying to throw together a sort of balance sheet — a quick-and-dirty assessment of major changes to biodiversity in Plummer’s Hollow from 1971-2007. There’s no denying the negative impact of white-tailed deer, earthworms, invasive plants, and poor land-use. In the last category, the near-clearcutting of the former McHugh tract destroyed 100 acres of the richest woods in the hollow (we were only able to acquire that property after the damage had been done). But other apparent disasters, such as the snowstorm I just mentioned, had a silver lining. The invasion of the gypsy moths in 1980-81, for example, killed a lot of mature oaks, especially on the drier ridgetops, but it created a lot of valuable new wildlife habitat. Red-bellied woodpeckers suddenly appeared and became year-round residents. My brother Steve began to notice more longhorned beetle species than ever before.

We have no shortage of interior forest-dependent bird species, including some that are declining elsewhere, such as cerulean and worm-eating warblers. There may be only half as many wood thrushes as there used to be, but we still have quite a few. And three species linked to more mature forest environments have become regular breeders in the hollow: black-throated green warbler, Acadian flycatcher, and solitary or blue-headed vireo. So the winter wren isn’t the only species that benefits from a hands-off management philosophy.

The Carolina wren is another avian newcomer within the past 20 years, though unlike its cousin, it prefers forest openings and dooryard habitat. The expansion of its range northward is most likely a response to the warmer winters associated with global climate change. A cold winter like the one we just had kills much of the Carolina wren population off, and it takes several years for them to rebound. Another southern species just getting established in our area in the last few years is the black vulture, which now seems to nest in the adjacent valley. We see them soaring up and down the ridge from time to time.

Common ravens were occasional visitors in the 70s; now they are year-round residents. Other breeding bird species we’ve confirmed in the last two decades include golden-crowned kinglet, black-throated blue warbler, and wood duck. And it’s hard for me to remember now, but wild turkeys were once scarce, too. Now they’re all over the place.

Many perennial wildflowers in the hollow have multiplied since I was a kid, probably a result both of maturing forest conditions and, in the last decade, of declining white-tailed deer numbers due to our successful hunter program. Purple trillium, Solomon’s-seal, yellow mandarin, pinesap, and mayapple are all more numerous, and wood betony and spring beauties have made their first appearances within the last ten and three years respectively. Some plants that used to be abundant when I was a kid virtually disappeared when deer numbers skyrocketed in the 80s and 90s, but are now beginning to rebound, including blackberries, raspberries, staghorn sumac, black elderberry, and Joe-Pye weed. The deer-sensitive red elderberry, never a common species in the past, has recently begun to appear all over the place in moister woods, and wild hydrangea and maple-leafed viburnum probably also owe their recent increase to the decline in the deer population.

The carpet of hayscented fern on drier slopes is a relatively new phenomenon here; I remember being excited by the first big beds of it back in 1978 and 79. Though native species, hayscented and New York ferns are behaving like invasives throughout Pennsylvania, spreading like wildfire and impeding the germination of other plants, including trees. A combination of deer herbivory and chemical changes in the soil (due mostly to acid precipitation) seems to be at fault. But at the same time, other, less aggressive ferns are doing well, too. Rattlesnake fern and cut-leafed grape fern both used to be rare, but they’ve become fairly common in the hollow now. It’s my impression that we also have a lot more cinnamon and interrupted ferns than we used to — both spectacular plants.

Where reptiles and amphibians are concerned, we seem to be doing O.K. Wood frogs have declined precipitously in recent years, but as I just explained in a post at the Plummer’s Hollow blog, that may be our fault for making their preferred ephemeral breeding pool a little too permanent, allowing predatory newts to gain a foothold. I’m not aware of any threat to wood frogs generally — though with so many other amphibian populations suddenly crashing around the world, one can’t be too sure. Eastern box turtles, on the other hand, are declining in many places due to habitat fragmentation and illicit collecting for the pet trade, so the fact that our population seems to be holding steady is very good news. We regularly find juvenile turtles, much to our surprise, because we have no shortage of mid-sized mammalian predators that like to snack on the eggs and young turtles.

Changes in mammal diversity here have been the most noticeable and dramatic in the past 35 years. Throughout the 70s, for example, there were no black bears on the mountain. We kept bees up until the mid-80s without a problem. Then the hives were destroyed by bears two years in a row, and we’ve had resident black bears ever since. In recent years, we’ve had two mother bears sharing this end of the mountain and raising litters of up to three cubs at a time. This reflects a state-wide increase in the black bear population, thanks to careful stewardship by the Pennsylvania Game Commission. Two other mammals are also much more common now than they used to be, bobcat and porcupine. Other than one, iffy sighting back in the 70s, bobcats were pretty much nonexistent here when I was a kid. But in the past three years, our hunter friends have begun seeing tracks, and two autumns in a row have had good sightings.

The porcupine population peaked about five years ago, I think, and started declining after that. Part of the reason for this decline may be the recent arrival of another species, one of the few that’s fast enough to flip and kill a porcupine: the fisher. This larger relative of the mink had been completely extirpated by trappers over a century ago, and was re-introduced first to West Virginia, then to north central Pennsylvania. We had our first sightings of a fisher in the hollow two years ago, which might seem like yet another vindication of our decision to foster mature forest conditions wherever possible. Fishers are supposed to be a mature-forest-reliant species. But apparently people are seeing them all over the place, and they are turning out to be much more flexible than the biologists had thought. In the second sighting in Plummer’s Hollow, a hunter watched one chasing a member of another species that’s new here, the fox squirrel. I can’t help wondering whether these big, slow squirrels will be able to hang on with fishers getting established — not to mention coyotes, which arrived on the mountain just a year or two after the fox squirrels.

The coyote is a new animal altogether, never resident in the east until the latter half of the 20th century. It’s not quite a substitute for the extirpated mountain lions and wolves, because it doesn’t prey on adult deer, but we’re still pretty excited to have it around. Eastern coyotes are larger than their western counterparts, having interbred with timber wolves in Quebec, but unfortunately they aren’t nearly as vocal. On rare occasions when I wake in the night to hear coyote song, I feel the way I felt this morning, listening to the winter wren: uncommonly blessed.

19 Replies to “Silver linings”

  1. when the weather allows for open windows
    I frequently listen to coyote songs
    in the deep of the night here
    in upstate New York

    a couple of years ago I was privileged to watch one trot across the back yard
    much bigger than I had ever thought coyotes were
    and a fantastic grin

    and last week Emily who lives with me
    on her way home on the back road
    spotted one at the edge of a field nearby
    stopped her car to sit and watch awhile

    there have also been bear sightings
    within the past few years

  2. Well, I’d be happy to trade some of our bears for a few of your coyotes! Though both are great to have around. Beautiful animals.

    All I can say is, though, you’d better keep those cats indoors!

  3. Interesting post. The Winter Wren is obviously quite fussy about its habitat in North America; over here, where it’s the only wren species, you find them everywhere—gardens, farmland, moorland, marsh. It’s vulnerable to cold winters, but usually it’s Britain’s commonest breeding bird.

  4. I’ve heard that. I wonder if DNA studies have been done to determine whether it is in fact the same species? (Though that’s still a subjective judgement, of course.) Out west, winter wrens apparently differ as well: their songs are a good deal longer than they are here. If it is all one species, it’s an unusually adaptable one. But I believe many birds are more adaptable than ecologists are willing to admit. I think reptiles and amphibians make much better focal species for conservation efforts, aside from the fact that they don’t always enjoy quite the public esteem that birds do.

  5. Really interesting; can’t imagine what it’s like to have such a diversity of species around, and such big buggers too – bears even. Wish I had a N. American wildlife book to hand…

  6. According to Wikipedia—not my ideal source for this kind of information—they have done DNA tests, and the populations are genetically distinct but not sufficiently to be different species. Taxonomists all seem to be splitters these days, though, so it may only be a matter of time.

  7. Lucy – That’s probably the main reason why I’m not too interested in relocating to Western Europe (which otherwise has a certain amount of appeal): I’m not sure I could handle the lack of wildness. Maybe Romania, where they still have wolves…

    Harry – Thanks for doing the research I should’ve done. I just did a search on the Bioabstracts database through Penn State, and while I didn’t find anything too helpful on taxonomy, I did find this interesting abstract to a paper by Donald Kroodsma, the birdsong expert:

    The songs of the winter wren in North America are long and complex, but consist of highly organized and repeatable sequences of different song units. Eastern and western populations differ markedly in complexity of song types and overall repertoire size. Two eastern males sang only 2 song types; 1 intensively studied Oregon [USA] male sang at least 30 stable song types; temporal and frequency parameters also gave the impression of greater complexity within Oregon songs. At both locations, though, neighboring males sang nearly identical song units or (especially in New York) entire songs, indicating that vocal learning is fundamental to song ontogeny. The complex song of the winter wren may be a product of intense sexual selection in a polygynous mating system. Further data on both mating systems and song complexity in different populations are needed before this hypothesis can be critically assessed.

    –“Winter Wren Singing Behavior: A Pinnacle of Song Complexity,” Condor, 82(4): 357-365 [1980]

  8. maybe you can help me, Dave
    a bird whose “song” sounds like creaking
    and who songs at night
    I had the windows up last night
    and that’s what I heard . . .

  9. I enjoyed the post — lots of great information. To be honest, I hadn’t ever realized there were coyotes in the PA woods until one night two summers ago I heard one. I asked Stacy, “What the hell is that?” “A coyote.” “A coyote?! Is it going to eat us?”

    Now in real life I’m not this stupid, but I grew up near the forest and always had nightmares that a lion would jump out of the forest, prance (?) up to the back porch, and try to claw and scratch its way into the house. (Presumably, to eat me.) So this somewhat over exaggerated question stems from childhood nightmares, and gets asks about quite a few harmless forest creatures.

  10. Thanks for the comment. I think it’s a good thing to be honest about our fears. And some degree of fear of the natural world is healthy, and grades into respect and awe. Unfortunately, we tend to be rather too fearful of things like black bears, that are extremely unlikely to do us any harm, and not nearly fearful enough of things we can’t see, such as dioxin, mercury contamination, etc.

  11. I keep hearing “painter” or “catamount” (Eastern Cougar) reports in western North Carolina–I can remember bobcats digging up the culvert at the base of our yard when I was a girl.

  12. marly – There are a lot of cougar reports here in PA, too. Virtually all of them are bogus, I’m sure, but there are (at the least) a few released captives running around. I would love to see a breeding population get established. Cougars evolved with deer as their principle prey species, and the huge populations of whitetails we have now could certainly support a cougar population, especially in the wilder, less heavily roaded portions of the east.

    Laura – Wood thrushes are in decline throughout their range, apparently due in part to the increasing fragmentation of interior forest habitat and proliferation of edge-dwelling nest predators (cowbirds, crows, raccoons, skunks, feral cats, etc.). Another factor may be acid depostion. A recent study at Cornell found that woods with very acidic soils (as on most wooded areas in PA) are iffy for wood thrush breeding success, because the females need a lot of calcium in their diets in order to be able to make good eggshells. They usually get this by feeding on snails, but the land snail populations are heavily impacted by acid deposition (and also, I would imagine, by the radical diminution of forest litter in areas where the forests ahve been invaded by non-native earthworms). This is probably true for some other forest-interior songbirds, too; wood thrushes just happened to be the focus of that study.

    patry – Thanks for reading.

  13. Thanks, Dave. I know of the overall decline of wood thrushes, but was interested in their decline at your place, while others like the cerulean are increasing there.

    I have to read up on the non-native earthworms – I don’t have a clue what that’s about.

  14. their decline at your place, while others like the cerulean are increasing there
    I don’t know, but it seems to be in line with what I’ve heard from other people studying songbirds in more-or-less intact forest: many species that are declining generally due to the loss of such habitat continue to thrive in remaining large patches, while a few, such as the wood thrush, decline even there.

    The New York Times article from last week was a good introduction to the earthworm issue. It’s no longer available for free from the Times archive, but the text was preserved here.

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