The 4 AM American Robin chorus is accompanied today by hip-hop. A bicycle flashing blue lights—on a speaker, I would guess—is playing some musical rap as its owner wheels it slowly about the murky streets.
Today is my last major breeding bird foray of the year. I’m planning to cover the northwestern side of the hotspot, always an exercise I put off because of the difficulty of getting there. At least the air quality has improved: the smoke disappeared overnight, to be replaced by muggy heat.
As I step out the front door at 4:35, Barn Swallows start chittering as if they’re skimming Pennsylvania Avenue, but I can’t see them anywhere. I cut through the bank lot and the junkyard, then cross the tracks under the I-99 overpass to access the corner of our property at the base of Sapsucker Ridge. There’s a more circuitous route I could take, but I want to get to the sit spot before the out-of-town chorus starts up, so I fight my way through a cindery thicket of tall privet following deer trails until I reach a rusty fence that seems like it was once purposed to keep deer from the interstate. I swing up over a partial break in it and continue through more privet until I finally reach an old road that once belonged to a nearby industry whose buildings were obliterated by the Tyrone Bypass, precursor to I-99, some 55 years ago.
The grassy road is just inside our property boundary with the Pennsylvania Department of Transportation and provide an excellent vantage point over Tyrone and points beyond. I snap out the chair and wait as Indigo Buntings get things going on the first day of the second half of the Plummer’s Hollow 200 (current total: 187 species).
The dawn chorus here consists of a few seconds of bird and a few seconds of truck, then bird, then truck: the four lanes are directly downslope, so I catch the traffic coming and going. And the trains! They roar through from both directions, five over the course of forty minutes, seemingly louder here than down below.
Right around five, a Song Sparrow joins in, then the first Gray Catbird cranks it up from a tree below me, just off the highway. More buntings, more Song Sparrows, a Northern Cardinal, more catbirds: the chorus here is distinct from the balcony, and so far, less diverse. The first Cedar Waxwing flies over at 5:35 to perch in upslope trees, and after a few minutes more, I can see Chimney Swifts crisscrossing the sky from here to the distant wind turbines on Sandy Ridge, the outer flanks of the Allegheny Plateau to the west, rising 1500 feet above Tyrone and considerably higher than Brush and Bald Eagle mountains at the Gap.
A Carolina Wren sings from across the highway, then the first of the day’s 88 Red-eyed Vireos. A Fish Crow potters about the downtown streets, and seven Mallards fly out of the Gap and veer south, following the valley. I’ve got a long way to go, so at six, I’m underway again.
Rose Hill
You may remember my mentioning that the two ridges holding up the sides of Plummer’s Hollow—itself composed of crumbly Juniata Sandstone—are comprised of erosion-resistant Bald Eagle Sandstone from the Ordovician period, forming Laurel Ridge on the east, and Tuscarora sandstone from the Silurian period on the west. On other ridges, the Bald Eagle forms ‘benches’ below the level of the Tuscarora, but here, close to that one-billion-year-old suture in the Earth’s crust that is marked by the Tyrone-Mount Union Lineament, things are different. A cluster of strike-strip faults allows the Bald Eagle-Brush mountain ridge to bend southward around the lineament; where the faults occur, irregularities allow road easier passage over the Tuscarora rock fields, such as to my south at Skelp (the ‘Skelp cut’) and to the northeast as well near the village of Bald Eagle. Smaller irregularities, known as fractures and fracture traces, create weaknesses in the rock that allow water, gravity, and other forces to do their work on the folds. A major weakness right at the TMU allowed a river to carve the Gap in the first place, and a stream to carve its way headward to create Plummer’s Hollow, perpendicular to the TMU. Over where I am this morning, the density of fractures led to slumps and collapses of the Rose Hill shale onto the Tyrone Bypass. I am about to have to cross the largest one, the ‘Big Slide.’ It’s a grassy, flat-bottomed bowl with cattail wetlands at the bottom and steep, shaly slopes covered by black locust. Our property border runs along the upper side.
As I approach the Big Slide, the unmistakable call of a Hollywood eagle issues from the forests above, and a Red-tailed Hawk glides out of the forest and across the interstate, disappearing into the fog southward. The grassy area itself is alive with the species I’ve already heard today, but nothing else: no Common Yellowthroats, no Field Sparrows, no Red-winged Blackbirds, no House Wrens or any other field or marsh birds one might expect to see in an area this size. I struggle up the far side through privet and barberry, and finally reach the old road system again, first constructed in the 1800s to reach iron mines and stone quarries.
Boulder Streams and Fossil Ores
Like many Appalachian ridges, Sapsucker has a distinctive form—steep at the crest, which is covered by Tuscarora bedrock, then draped by ‘rock slides’ composed of Tuscarora sandstone boulders, often glittering with white and pink quartz and coated by ancient lichens. The slides are sometimes called ‘talus slopes’ but in reality are boulder streams. The rocks all broke off the higher parts of the ridge in the freeze-thaw conditions of the Pleistocene, when we were so close to the continental glaciers that the extreme weather almost literally melted the mountains down. Tens of feet of elevation were lost as the hillsides slumped, and the streams of boulders, moving at imperceptibly slow speeds over thousands of years, blanketed the younger Silurian formations underneath them. At their steepest parts, the streams are bare rocks with at best clumps of scraggly birches, mountain laurels, ferns, and moss, but lower down, as the slope becomes gentler, the cover becomes thicker and the forest more diverse, thanks to the topsoil that has been able to accumulate.
The cover on top of bedrock on hillslopes is called ‘colluvium.’ Like the alluvium in valleys that is deposited by rivers and allows farming, colluvium can have rich and deep soil. Here, the colluvium on Brush Mountain’s northwest slope drops down all the way to the Little Juniata River, or would if it hadn’t been removed to make way for the bypass.
In most places here, because Tuscarora colluvium covers the younger Rose Hill formation, the only places to see the Rose Hill’s shale and the fossils it holds is where the bypass slumps occur or where other human-caused disruptions have exposed it. Back in the colluvium woods, that means elongated mounds of it that were dug out from underneath the sandstone boulders 150 years ago to get at a layer of sandstone, a deeper layer of the Rose Hill containing what is known as ‘fossil ore,’ that is, rock containing hematite or iron ore.
Even before these colluvial slopes were accessed for ore (to little success—it was much less productive than other types of ore found in nearby limestones), haul roads had already been built for charcoal for the Juniata iron industry almost fifty years before the railroad came through. Before the Big Slide, one could still follow the original haul road from the Gap side of our property all the way around the mountain.
Even after the old-growth forests were converted to furnace fuel (2800s-1810s) and the hillside probed for hematite (1810s-1870s), the colluvium was not left at peace. Next came the building stone industries, and that is what turned the entire lower slope of the ridge, and even some of the steepest parts near the crest, into a maze of rock piles and crude trails. Whole buildings like the Armory in Tyrone, and many of the town’s home foundations, were built with rock from Bald Eagle and Brush mountains. Ganister—rock to line iron furnaces—was also taken out. Near the Big Slide, the landscape is so broken that original gentle slope of the colluvium has been lost in a pockmarked and pitted wilderness.
The good news in all of this is that the forest is diverse and old, so the birds—those that can stand the constant roar of traffic—are more characteristic of deep hollows than what you might picture along a major transport route. I am surprised, however, at the number of Wood Thrushes here, and as I go along and the forest gets older and larger, they are joined by abundant Scarlet Tanagers, Ovenbirds, Hooded Warblers, Eastern Wood-Pewees, and even Worm-eating Warblers, a species I would not have expected here.
The second slide—more of a slump—to the south is smaller and less steep than the first, but far wetter; so wet, in fact, that it is has a cattail marsh growing on its shaly, super-saturated rim. All around are thickets of barberry. I try to skirt the edge of the forest, but the invasives are mostly too thick, and the going is made even rougher, despite the old roads, by the tree-clogged drainage systems and decrepit fences associated with the bypass.
The Oldest Growth
At 7:30, I arrive at the southwest corner of our property. Half a grove of two-century-old giant red oaks dating from the original logging is still standing; the southern half was obliterated by a logger some years back. On the neighboring property, invasive ferns and grasses coat the forest floor under young trees; on our side, towering oaks and sugar maples are beset by vines and the forest floor is scattered with moldering logs. A colluvium boulder from far upslope, the largest rock in the hotspot, lies incongruously in one spot.
The near-old-growth pocket here, despite the interstate noise, is notably richer in avifauna than the surrounding woods. Several families of Hooded Warblers, Worm-eating Warblers, and Ovenbirds buzz and chip about the tangly light gaps, quite agitated by my presence.
So far, this hike has boosted hotspot breeding numbers for Wood Thrushes, tanagers, the above-mentioned warblers, Rose-breasted Grosbeaks, and Indigo Buntings, not to mention Northern Cardinals, Song Sparrows, and Eastern Towhees. But what it has also revealed is the utter lack of Field Sparrows and Common Yellowthroats, two species that are abundant just on the other side of the ridge, in First Field. I would have thought, with the amount of edge habitat and marshy spots all along this side of the hotspot, that field species would thrive, and I wouldn’t have guessed that deep woods species would be able to tolerate the noise.
July Feels Like July
Now it’s up and over. I pick a spot with smaller rocks to make the arduous climb to the ridge crest, but the 94% humidity makes it tough going. The middle level of the ridge is a quiet zone, with Worm-eating Warbler trills, Ovenbirds, and pewee laments fading below and the distant sounds of Black-and-white and Black-throated Green warblers from above.
I reach the crest and the first exposure to the hazy rays of the 8:15 sun right above the corner of First Field. The difference between Tuscarora and Juniata couldn’t be more stark: behind me, a woods of black gum, black birch, red maple, and oaks nearly devoid of understory, and in front, a jungle of mile-a-minute, barberry, stilt grass, and hay-scented fern draping the grape tangles and tumbled-down black cherries.
Purple Martins cavort over the spruce grove, which is popping with families of Chipping Sparrows, Indigo Buntings, Common Yellowthroats, Field Sparrows, Blackburnian Warblers, and Golden-crowned Kinglets. I head quickly downhill, past the houses and into the Hollow, ticking off other species for the July list: Northern Parula, Brown Thrasher, Eastern Bluebird, Yellow-throated and Blue-headed vireos, and so forth. Once again the Scarlet Tanagers, at 29, overwhelm the expected eBird numbers, and surprisingly, at 7, so do the Blackburnian Warblers. A Cooper’s Hawk, which apparently bred again this year, calls, sounding like it is being harassed by American Crows.
As I go deeper in the Hollow, passing through the territories of Louisiana Waterthrushes and Acadian Flycatchers, the gnats become nearly unbearable as deer flies, frustrated by my broad-brimmed hat, circle overhead. Ah, July!
After six miles and almost six hours, the morning ends back at the balcony with 64 species. As rain showers set in, I collapse to nurse my sore back.