Snowbirds

"Peekaboo," by Scott M Duncan in NE Ohio (Creative Commons BY-NC-SA license)

It was a fine early December day — 18 degrees with partial sunshine and a howling wind.  A new half-inch of snow covered the ground.  I counted the birds at my feeders because it was a Project FeederWatch day.  For over 20 years, two days a week from November until early April, I’ve been counting birds for this Cornell University Laboratory of Ornithology program.  On that day, I recorded a record 16 species of birds — 24 house finches, two American tree sparrows, a song sparrow, two white-throated sparrows, a swamp sparrow, 25 American goldfinches, 19 mourning doves, a pair of white-breasted nuthatches, a pine siskin, four tufted titmice, two black-capped chickadees, a male downy woodpecker, two red-bellied woodpeckers, a purple finch, and 50 dark-eyed juncos.

Fifty dark-eyed juncos!  It was a challenge to count them as they swarmed over the ground and back steps beneath the feeders, looking like giant black and white ants, and pushed the other ground feeders to the periphery.  I had hit an all time high junco count and the Project FeederWatch website questioned my number when I entered my results.  That’s because over half of FeederWatch participants report six juncos or less.  Last winter my average junco group was 40.2.  The other bird species averaged .5 to 3 except for pine siskins (17.8) and American goldfinches (17.2).  Furthermore, when we conducted our Christmas Bird Count on foot over our mountaintop property, we tallied 208 species.  And, by January, sixty juncos were visiting my feeders.

According to most sources, winter junco flocks consist of 15 to 30 birds and settle on 10-acre territories.  During the day, they go from food source to food source, looking for a variety of wild seed sources to sustain them through the winter. The millet, milo, and cracked corn they prefer at feeders merely supplement the 5000 seeds they must consume every day from wild sources such as lamb’s quarters, thistles, broom sedge, ragweed, foxtail, and chickweed.  Our unshorn First and Far fields and home grounds provide a wealth of such seeds.

Junco tracks in Plummer's Hollow (photo by Dave)

Then, as the day darkens, several juncos seek shelter in our juniper tree near the feeders, but most head for our three-acre Norway spruce grove at the top of First Field.  One of my winter pleasures is sitting at dusk on Alan’s Bench, which is enclosed by spruces, and watching the juncos stream in from all directions.  At first they “zeet, zeet” to protest my presence, but they soon settle down beneath the sheltering boughs.

We aren’t far from the nearest breeding area for dark-eyed juncos — the Allegheny High Plateau — so I suspect that’s where our juncos, at least the earliest arrivals in late September, come from.  But as their numbers increase, many may be migrating from as far north as the boreal forests of Canada.  Traveling from 30 to 200 miles a night, how far juncos migrate depends on the weather, the lateness of the season, and the amount of body fat they have stored.  In Pennsylvania female juncos move southward ahead of males and adult females before young females.  In fact, adult juncos winter farther south than youngsters and those young migrate later than the adults do.  But we have plenty of the spiffy, dark gray to black males as well as the duller gray females and young, all of which have snowy white bellies.

When I first studied birds, our juncos were called slate-colored juncos.  But in the 1970s, ornithologists lumped five species of juncos into one and renamed them dark-eyed juncos.  However, the ornithologists designated those former five species — slate-colored, white-winged, Oregon, gray-headed and Guadalupe — as groups.  Our slate-colored junco is by far the widest distributed of the groups, breeding from Alaska to Newfoundland, as far south as Texas and along the Appalachians to North Carolina and northern Georgia.  Within the slate-colored hyemalis group are three subspecies— Junco hyemalis hyemalis, J.h.carolinensis, and J.h.cismontanus.  Here in Pennsylvania we have both J.h.hyemalis and J.h.carolinensis, the former in the northern glaciated and high plateau areas, the latter in the more southern portions of the state, especially in the mountains of Westmoreland County at the Powdermill Nature Reserve, where they have carried out field and banding studies of juncos since 1983. Of course, for mere amateurs like me, telling these subspecies apart in the field is impossible.

Because our juncos reminded European taxonomists of their reed bunting, they named them Junco, which means “reeds” in Latin.  Hyemalis is Latin for “winter.” But many folks still know dark-eyed juncos as “snowbirds.”  Other popular names include “black snowbird,” “common snowbird,” and “eastern junco.”  Henry David Thoreau, writing his journals in the mid-nineteenth century, referred to them as “blue snowbirds,” “slate-colored snowbirds,” and “slate-colored sparrows.” John James Audubon wrote in 1831 that “there is not an individual in the Union who does not know the little Snow-bird.”  Probably they were called snowbirds because most people only saw them in winter when the birds left the forests for parks, rural roadsides, farms, and today for backyard birdfeeders.

Dark-eyed junco by Tom Davis in Wilmington, Delaware (Creative Commons BY-NC-SA)

Not only do juncos visit more feeders across the continent than any other species, but also they are incredibly abundant — an estimated 630 million strong.  Because they flock together during the winter, their winter social behavior has been a popular subject for researchers.  In these flocks, males dominate females, and within each sex, adults dominate youngsters.  You can observe this at feeders when birds lunge at other birds and flick their tails, exposing their white outer tail feathers.  Those males with the most white in their tails are the most dominant.  Usually, this behavior occurs in early morning or late afternoon when they are feeding more heavily, especially when it is very cold or snowy.  Those dominant birds feed in the middle of the food area, and it’s up to the subordinates to look out for predators.  They also get less to eat, which is a problem if food is scarce, but if food is abundant, both subordinates and dominants thrive.

By March, junco males have joined our spring bird chorus, their trills making a “lovely tinkling chorus… as if a myriad of woodland sprites were shaking little bells in an intensive competition” Canadian naturalist-writer Louise de Kiriline Lawrence once wrote.  The males leave ahead of the females and by late April, our last junco is gone. By the time the females arrive on their breeding grounds, the males have established a two to three- acre territory.  At first, they chase returning females.  But if one stays on a male’s territory, he begins courtship by fanning his wings and tail, continual hopping, and picking up nesting materials.

Those males with the most white in their tails are most attractive to females.  They also have the highest testosterone levels.  But do they make the best mates?  According to researchers Ellen Ketterson and Joe McGothlin, that depends.  Those males with the highest testosterone levels attract older, more experienced females because their songs are sweeter.  They also produce more offspring.  However, they are not very good fathers, and their offspring are smaller when they hatch and die at higher rates.  The fathers are too busy displaying and chasing after other females to feed their mates or offspring as often as the less testosterone-charged males.

The dominant males also die sooner. Often, they are too busy showing off to be wary of predators. In addition, their elevated testosterone increases their stress, which leads to the production of a hormone called “corticosterone,” That hormone gives them quick energy even while it breaks down protein, leaving them with atrophied feathers, muscles, and organs.

Junco nest in Vermont, by Kent McFarland (Creative Commons BY-NC license)

Despite this dominant male junco angst, most pairs practice social monogamy and raise two families a year.  The female chooses the nest site and builds the nest.  Most sites are constructed on or near the ground in a bank or rock face, especially if grass or other vegetation overhangs it.  The nest we found in Little Pine State Park along the Lake Shore Trail last May was in a road bank under a bower of dried leaves caught in several small branches.  My husband Bruce, 13-year-old granddaughter Eva, and I saw a bird fly out of the bank.  Eva quickly found and photographed the nest woven of dried pine needles, twigs, and grasses, which contained four pale blue eggs strongly marked with brown squiggles and a brown blotch at the large end.  We stood quietly, waiting for its owner to return, and soon heard and then saw a scolding junco nearby.  The park, a forested gem with a small dammed lake in Lycoming County, provides excellent habitat for nesting juncos.

Cordelia Stanwood, an amateur ornithologist and photographer who lived in coastal Maine during the early twentieth century, wrote that “the nest site varies according to its situation.  I have seen juncos brooding amongst the roots of a growing clump of gray birches, partially under stumps and rocks, below a tuft of leaves, in a brush heap shaded by small evergreens, beneath bracken, and many within the side of a bank or knoll, the wall of a knoll covered with bird-wheat moss, or the side of a steep bank just under the overhanging sod [which] seems to be the most typical site for a junco nest.  A depression is made or enlarged in the side of the bank or knoll, and the moss or overhanging sod form a natural roof.”  Exactly, except that juncos also build unusual nests such as on a ledge beneath a house gable in Nova Scotia, in a half-pound tobacco can lying on its side in Saskatchewan, in a wind-vane bird feeder mounted on an eight-foot iron pipe in Olean, New York, and, for two years, in a hanging planter in Trucksville, Luzerne County, Pennsylvania.  The second year the female nested in April while Christmas greens were still in the planter and nested a second time, after the first nestlings fledged, in the planter when the greens were removed.

The female incubates the three to five eggs 12 to 13 days while the male warns of danger, keeps small birds from the nest, and tries to discourage eastern chipmunks, which are major nest predators.  Red and gray squirrels, deer mice, white-footed mice, jumping mice and weasels also threaten eggs and nestlings in some areas.

After the junco eggs hatch, usually within a few hours of each other, the nestlings quickly mature as both parents stuff them with mostly insects and spiders.  At 12 days of age, they leave the nest, although if they are disturbed, they can run off at nine days old.  Fourteen days later, they are able to fly well and feed themselves.

Then they are on their own and later join winter flocks.  It they are lucky they will evade a host of predators, including accipiters — especially sharp-shinned hawks — shrikes, owls, jays, feral and domestic cats particularly near bird feeders.  More than once in the winter I’ve watched a sharpie catch, kill, pluck, and eat a junco near our feeders.

But such occasional predation doesn’t seem to shrink our junco population.  Because they are such generalists in nesting habitat — breeding in coniferous or deciduous forests — and in winter habitat continent-wide, as well as in their food choices, dark-eyed juncos should remain a ubiquitous species for decades to come.

Dark-eyed Junco by Birdfreak.com, Rockford, Illinois (Creative Commons BY-SA license)

A Fruitful Year

Some years are more fruitful than others.  Last year was one of those years.  From mid-June until mid-August I never set out for my morning walk without slipping a pint jar into my pocket.  I wanted to be prepared to pick first the low bush blueberries, then the huckleberries on the powerline right-of-way, and later, in August, the blackberries that overhung the Far Field Road.

But for nearly three weeks in July, most of my berry-picking centered on our home grounds where, for the first time in more than two decades, black raspberries escaped most of the ravages of deer and the attention of black bears and produced a crop that I could barely keep up with.

Video of Marcia picking raspberries in 2008. (Subscribers must click through to watch.)

Back in 1971, when we first saw our place on a Fourth of July weekend, I couldn’t believe the abundance of black raspberries growing in the backyard. Over the years, as the deer herd increased, the black raspberry canes decreased. Then, the bears appeared. Those canes that survived the browsing of the deer, namely those growing on the steep slope below the front porch, were trampled by bears overnight and stripped of their almost-ripe fruit.

The ubiquitous white-tailed deer

During the last several years, our hunters have trimmed the deer herd and the black raspberries have begun to recover.  Last summer we had a perfect storm of berries — patches outside the kitchen door, below the front porch, surrounding the springhouse, on a steep slope beside the guesthouse, and in the guesthouse backyard.  Secondary patches thrived beside the driveway and in our side yard.  Every hot, humid morning I was out early, picking several quarts.  Although some went into the freezer for winter fruit salads, we ate most at our meals, either alone or combined with blueberries and huckleberries, depending on whether I had the strength and will to pick both in one day.

The word “fruit” comes from the Latin fructus meaning “that which is used or enjoyed,” and we certainly did both with our wild berry crops.  I did most of the picking.  Occasionally, I was rewarded with more than berries.  Once in the patch outside the kitchen door I found a song sparrow nest that contained four greenish-white eggs heavily blotched with brown.  While picking blueberries on the powerline right-of-way, a tiny American toad hopped in front of me.  Hooded warblers serenaded me as I harvested blackberries on the Far Field Road.

With all the bears on our mountain, I was surprised that they left the black raspberries alone and that I never encountered them amidst the blueberry and huckleberry shrubs.  No doubt, the incredible abundance of wild berries everywhere on our mountain kept them busy.  I, after all, ranged only a mile or so in search of berries, but I knew of other patches on neighboring properties that had as much or more berries than our property and that were not picked by humans. And the bear scat on our trails certainly showed evidence that they were enjoying berries as much as we were.

Not only did the wild fruit crops palatable to humans thrive.  So too did those palatable to birds and animals, such as the red-berried elder, also called mountain elder. This beautiful, native shrub likes cool, moist, rocky woods and blooms in April.  On steep slopes, where deer cannot reach to browse its twigs and foliage, red-berried elder thrives, bearing pyramidal clusters of berry-like drupes here by the sixteenth of June.  Our son, Dave, photographed chipmunks eating them, and I have watched rose-breasted grosbeaks gobbling them up.

chipmunk with red elderberries

The naturalist-writer Henry David Thoreau once wrote in Faith in a Seed, “If you would study the habits of birds; go where their food is, for example, if it is about the first of September, to the wild black-cherry trees, elder bushes, pokeweed…” The “elder” he meant is the common elder, those shrubs with flat-topped, clusters of small, white flowers that  are even more popular wildlife food.  By early September, those shrubs inside our three acre deer exclosure hung heavy with the umbels of purplish-black, berry-like drupes, and I flushed two ruffed grouse feeding on them.

Because common elder blooms long after the last frost — in late June and early July — it always produces a bumper crop of fruit.  “Many species of wild birds are attracted to the ‘banquet table’ which the common elder spreads in the fall,” William Carey Grimm wrote in The Book of Shrubs, such as gray catbirds, American robins, eastern bluebirds, northern cardinals, rose-breasted grosbeaks, eastern towhees, red-bellied woodpeckers, brown thrashers, and wood and hermit thrushes.  But because white-tailed deer browse on its twigs and foliage, the “common” elder has become uncommon in many areas. What the deer don’t eat, the sprayers of roadsides, drainers of swamps, loggers of stream sides, and abolishers of fencerows destroy, because this is a shrub of fencerows and waysides that flourishes in rich, moist soils along streams and swamps.  Those in our exclosure grow along its moist border, reaching a height of seven feet, while those that grew along our stream at the edge of our First Field wetland are gone because of deer browsing.

Wild black cherry trees are not deer food so we have many in all stages of growth including large trees. As early as the second of July, I flushed a brown thrasher fledgling that was eating wild black cherries from a medium-sized tree at the edge of First Field.  But it was mid-August before most of the cherries in the forest began to ripen.  Then they were loaded with fruit, some of which were green, some red, and some black.  Common grackle flocks quickly discovered them, and during an evening walk, my husband Bruce and I watched hundred of blackbirds stream over First Field and land on Sapsucker Ridge, their black bodies silhouetted against a golden sky as they ate cherries.

Cedar Waxwing in an ornamental cherry tree (photo by m. heart, Creative Commons Attribution-Noncommercial license)

The following day, Tim Tyler, one of our hunter friends, was cutting out black locust trees on First Field when he discovered a cedar waxwing nest with four pale gray eggs spotted with brown in a locust tree.  He immediately stopped cutting there and left a small grove of six trees standing to protect the incipient waxwing family.

Thoreau wrote about finding a small black cherry tree in “full fruit” and hearing the “cherry-birds — their shrill and fine seringo — and robins… The cherry-birds and robins seem to know the locality of any wild cherry tree in town…” “Cherry-birds” are cedar waxwings. Had the waxwings waited for the cherry crop, which was unusually late because of a cold spring, before starting their family?  They do, after all, feed fruit to their nestlings. On the other hand, it could have been a second nesting.  Successful cedar waxwing couples often have second families, especially during good fruit-bearing years.

I kept an eye on the nest from a distance and always saw the female sitting on it.  But on the fifteenth of September, a cedar waxwing keened from the bare branch atop one of the tall black locusts above the nest site.  It looked around alertly, as male cedar waxwings do when they are on guard for their family. I peered at the nest through my binoculars and saw the female on the nest as usual.  Then she flew up toward the male and both of them flew off.  I took the opportunity to check their nest and found four nestlings.  One looked more advanced than the others did, but this sometimes happens with waxwings because often the female starts incubating before she lays all her eggs.

That was the only time I went near the nest, but I continued to watch it from a distance.  Soon the nestlings’ little crested heads were visible above the rim of the nest.  At least one parent was on guard in the tall locust whenever I walked past. Based on my calculations, that the female sits 12 days on her eggs before they start to hatch—a process that can take form 48 to 96 hours—and another 16 days as nestlings, I expected them to fledge around September 24.

Sure enough, on the morning of September 24, the cedar waxwing nest was empty except for a broken egg still holding smelly liquid and two squished wild black cherries.  The nest had been woven of wild grape stems, lined with dried weeds and plastered on the outside with fluffy white material.

In addition to cedar waxwings, I saw red-eyed vireos, blue jays, and scarlet tanagers harvesting wild black cherries, but the list of songbirds and other wildlife that feast on them is legion.  Thoreau mentioned gray catbirds, brown thrashers, eastern kingbirds, blue jays, red-headed woodpeckers, eastern bluebirds and northern cardinals as the most common birds that eat wild black cherries, in addition to robins and cedar waxwings.  Huge piles of bear scat studded with cherry pits on our trails testified to their popularity with bears. And the smaller animals, such as foxes, squirrels, and chipmunks, also ate the fruit.

A bower of pokeweed above Coyote Bench ripened too in September.  Pokeweed, known by many alternative names, for instance, pokeberry, poke, redweed, inkberry, and pigeon berry—can grow up to 12 feet tall in rich, moist soil.  Its long clusters of dark purple berries and large shiny seeds are popular with many songbirds, especially mourning doves, hence its name “pigeon berry.”  Philadelphia-based bird artist, Alexander Wilson, wrote back in the early nineteenth century that “the juice of the berries is of a beautiful crimson and they are eaten in such quantities by these birds [robins] that their whole stomachs are strongly tinged with the same red color.” I’ve watched eastern bluebirds harvesting the berries from pokeweed growing beside our house.

Solomon's plume (AKA false Solomon's seal) in berry

Several of our spring wildflowers flaunted autumn fruit also.  In mid-September, I walked down our road and found twin orange berries hanging from the end of yellow mandarin stems.  A series of twin blue berries dangled beneath Solomon’s seal stems, bright red clumps of jack-in-the-pulpit berries bent over from their weight, and a string of pinkish-red berries hung from the stem ends of false Solomon’s seal.  Wild spikenard displayed upright clusters of wine-colored berries.  Even the small beginnings of maple-leaved viburnum shrubs had a few dark, bluish-black clumps of berries.

But the wild nut crops were thin or non-existent, probably due, in part, to a cold spell in late spring.  No wonder wildlife was busily harvesting the September fruit crops. Because nature often gives bounteously with one hand and takes with another, the more diversity we have in wildflowers, shrubs, and trees in our forests, the more likely the animals and birds are to find enough to eat even if a major food fails.
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All photos were taken by Dave in Plummer’s Hollow except where indicated otherwise.

An Enigmatic Warbler

Cerulean Warbler in Silver Maple swamp (by Petroglyph, on Flickr - CC BY-NC-SA license)

“Wee, wee, wee, wee, bzzz” sings my favorite yard bird.  For two months most years — mid-May to mid-July — the male cerulean warbler sings his monotonous song from dawn until dusk. The first year this happened, back in 2002, I worried that he hadn’t found a mate.  Why else would he sing on and on like some demented suitor?

Then I did a little research and learned that on their breeding grounds territorial male cerulean warblers are “vigorous and persistent singers, usually singing from the highest available forage,” according to Jon Dunn and Kimball Garrett in Warblers.

Other researchers reported that ceruleans often have favorite song perches in trees that leaf out late such as bitternut hickories, black walnuts and black locusts.  They hypothesize that the leafless trees allow the birds to broadcast their songs with little “acoustic hindrance” until late in the breeding season. And, in the case of our yard trees — black locusts and black walnuts — when they do leaf out their foliage is relatively thin.

Despite their glorious blue heads and backs, their white wing bars and bluish-black chest bands that stand out against their white throats, breasts, and bellies, male cerulean warblers can be difficult to spot high in the treetops.  And I can’t ever remember seeing the greenish-blue females with pale yellow underparts, which is why I thought the singing cerulean was an unrequited lover.

“A bird more difficult to observe I have rarely ever met with,” wrote a frustrated observer in 1919.  “Had it not been for the almost incessant singing, being heard almost constantly from daybreak until nearly dark, the task of identification would have seemed hopeless.”

Yet, in my case, seeing was believing, because for years I didn’t think we had breeding cerulean warblers.  In the 1970s and 80s cerulean breeding habitat was thought to be exclusively lowland open forests near streams or in old growth bottomland forests. Then one June day I saw a cerulean warbler in a tree beside the Far Field Road, and I wondered if they could be breeding on our dry mountaintop.

Cerulean warbler at nest (photo by US Forest Service - public domain)

As if in answer to my question, during the first Pennsylvania Breeding Bird Atlas Project, my son Mark confirmed breeding ceruleans on our dry mountaintop in 1986 despite the Project’s Handbook, which described cerulean habitat as “mature moist or riverside forests.”

Even since, I have found singing ceruleans somewhere on our mountain every spring and summer.  So far, the earliest return date I have recorded for them is April 30 and the latest singing date July 21.  They have sung above Greenbrier and Ten Springs trails in this century, a decade after a previous owner poorly logged that portion of the property.  But he did leave bitternut hickories, a few large oaks, and several tulip trees, which may have lured ceruleans.

Other ceruleans have sung at the upper edges of both the First and Far Fields, along the powerline right-of-way, in the Far Field thicket, beside the deer exclosure, in tall trees behind our old garden site, in the black cherry forest near the spruce grove, and along Laurel Ridge Trail — all dry ridgetop sites and all in edge habitat. I have not found them along our stream in our 100-year-old deciduous forest.

Luckily, Paul B. Hamel published an updated account of cerulean warblers, based on more recent research, in The Birds of North America in 2000.  In it, he wrote that ceruleans also breed in upland deciduous second-growth as well as mature forests at elevations up to 3,000 feet. But his 19-page article had many life history gaps, and he admitted that the cerulean warbler “has been little studied.”

Because they nest high in large trees such as oaks, they are difficult to observe.  What researchers do know is that despite expanding their breeding range into the Northeast from the Mississippi Alluvial Valley and Cumberland Plateau of eastern Tennessee, eastern Kentucky, and southern West Virginia, they are one of the fastest declining songbirds (70% in 40 years) in North America.

Cerulean Warbler in Rondeau Provincial Park, Ontario, Canada (photo by Mdf, Wikimedia Commons - GFDL license)

In the same year that Hamel’s account was published, ornithologists Kenneth V. Rosenberg, Sara E. Barker, and Ronald W. Rohrbaugh of the Cornell Laboratory of Ornithology submitted An Atlas of Cerulean Warbler Populations: Final Report to USFWS: 1997-2000 Breeding Seasons [PDF]. Two hundred field persons, both volunteers and professionals, collected information on breeding ceruleans and the habitats and dominant tree species they preferred.  They canoed navigable waterways, drove along rural roads, hiked portions of the Appalachian Trail, and drove and hiked through forests and isolated woodlots from Illinois to Missouri, New Jersey to New England, eastern Tennessee to Ontario, Canada.

They located 7,669 cerulean warblers at 1,923 sites in 28 states and Ontario.  Not surprisingly, almost all the ceruleans were singing males.  They also searched 355 likely sites where they didn’t find any ceruleans.  Some states had many more volunteers than others. Unfortunately, Kentucky, which is thought to be a major breeding site in its eastern section, had very few volunteers.  But Tennessee, another important breeding area, reported the most ceruleans (1210), followed by West Virginia (1124), New York (1068), Illinois (1000), and Pennsylvania (548).

I was particularly interested in the Pennsylvania findings.  After all, Philadelphia-based bird artist, Alexander Wilson, first named and then painted the male cerulean warbler (Dendroica cerulea) after it was discovered in eastern Pennsylvania, and Titian Peale, another Philadelphia artist, painted the first female cerulean, which had been taken along the banks of the Schuylkill River in 1825.

Alexander Wilson's cerulean warbler

It turns out that eastern Pennsylvania is still a hotbed of ceruleans in the Delaware River Valley on both the Pennsylvania and New Jersey riverbanks with 90 birds. This was followed by the Jennings Environmental Center and Moraine State Park in western Pennsylvania (69), the Juniata River and vicinity (42) and Peter’s Mountain and State Game Lands #211 (29), both in central Pennsylvania.  The habitats included dry slopes, riparian and lake margins.

Despite the 90 in the Delaware River Valley and the 71 in central Pennsylvania, ceruleans have historically been most numerous in southwestern Pennsylvania. Intensive surveys in that area and adjacent West Virginia found 1,400 ceruleans in what the report called “the heart of the species’ range.”  Almost as many ceruleans were found on dry slopes or ridgetop sites as in riparian or other bottomland habitats.

I was especially intrigued by the Juniata River and vicinity number in Huntington and Blair counties, since our Little Juniata River that we cross at the bottom of our mountain whenever we go out is a tributary of the Juniata River and our home is in northern Blair County. I also noted that the favorite nesting trees in dry upland sites were white and red oaks, black cherry, and maples, all of which we have as 100-year-old or older trees on our property.

In addition, ceruleans seem to prefer a tall, but broken tree canopy and large wooded tracts of at least 50 to 75 acres, but 1,300 acres is considered optimal.  Still, while those ceruleans in the Southeast use large forest tracts, those in the Northeast often breed in much smaller forests.  And in eastern Ontario maple forests of 25 acres are adequate.  So cerulean warblers may be more adaptable than previously thought.

On the other hand, their numbers keep falling at the rate of 4% a year.  Habitat loss, both on their breeding and wintering grounds, seems to be the major reason for their steady decline. Here in North America on their breeding grounds in eastern Kentucky and southwestern Virginia, mountaintop removal to mine for coal is permanently destroying mountaintop forests where ceruleans breed.

Forestry practices, as they relate to cerulean warbler habitat, have also been studied in southern Indiana by Sarah M. Register and Kamal Islam, and they concluded that “cerulean warbler habitat needs appear to be supported by 20-30 year cutting cycles combined with uneven-age management and timber stand improvement practices.”  Furthermore, clear-cutting results “in immediate habitat loss for cerulean warblers and other interior forest dwelling birds that may take years to regenerate.”

John James Audubon's Cerulean Warbler plate

On their wintering grounds in the subtropical forests of the Andean valleys in Columbia, Venezuela, Ecuador, and Peru, shade coffee plantations that provide excellent habitat for ceruleans are being replaced by sun coffee farms which are more profitable.  Deforestation in those countries is also due to cacao and tea plantations as well as to the illegal coca trade.

In summary, Hamel says that “Land-use changes brought about by increasing populations in the breeding, migratory, and winter ranges of this species appear to be the underlying cause of the population decline of the bird…”

Here in Pennsylvania the current move to put industrial wind farms on our dry, forested mountaintops will lead to fragmentation of many of our best remaining wild areas, especially in the ridge-and-valley province.  This will not only affect cerulean warblers but many other forest-interior nesting birds.  What a pity it would be to lose what researchers in eastern Ontario call the “enigmatic Cerulean Warbler.”

Those same researchers managed to find and observe 201 cerulean nests in a second growth, 80 to 90-year-old deciduous forest of mostly sugar maple, bitternut hickory, and ash trees from 1996 to 2001.  They discovered that cerulean nest-building, by the females, takes four to seven days, egg-laying seven days, and incubation 10 to 12 days.  While the females do all the incubating and brooding, the males and females feed the three to four nestlings.  Their major predator was the blue jay.  Other studies mention cowbird parasitism as a threat, but in Ontario, despite high cowbird numbers, the researchers never observed ceruleans feeding cowbird nestlings or fledglings.  The couple of nests that had cowbird eggs were abandoned by ceruleans.

Cerulean nests are usually constructed of bark fiber, fine grass stems, weed stalks, and fine hairs.  They decorate the outside of their nests with gray or white material, such as gray shreds of bark or spider webs.  Cerulean females anchor their nests on horizontal deciduous tree limbs 30 feet or higher from the ground beneath clumps of leaves.  Researchers both in Ontario and the Mississippi Alluvial Valley have banded ceruleans and have had banded birds return to the same breeding area at least two years in a row.

That convinces me that the particularly vocal cerulean warbler who sang in our yard in 2002 and 2003 was the same bird.

Cerulean Warbler, Shawnee State Forest, April 26, 2008 (by semillama on Flickr - CC BY-NC-ND license)

Narnia Interlude

In winter, it’s all about the weather, especially in February when we are liable to experience a confusing mixture of balmy, spring like days, sleet, freezing rain, and snow.  Last February 1 the predictions were so dire that all the public schools and colleges were closed.

The “tick-tick” of sleet against our windows began at 4:30 in the morning, and by dawn our brown earth was once again white — a hard, crusty white — that sent birds into the feeder area by the dozens — four common redpolls, 24 American goldfinches, a blue jay, a pair of red-bellied woodpeckers, another of northern cardinals, seven quarreling house finches, nine American tree sparrows, three white-throated sparrows, 12 dark-eyed juncos, three tufted titmice, a pair of black-capped chickadees, another of white-breasted nuthatches and 21 mourning doves, one of which dragged a shredded tail along behind it.

Once two white-tailed deer ran along the flat area below our back porch, paused to glance behind them, and then bounded on up Laurel Ridge.  I stood watching at the window for many minutes, hoping to see what had sent them off in a panic, but no other creature appeared.

From 27 degrees at dawn, the temperature gradually rose and the sleet changed to freezing rain, encasing every tree branch in ice. More and more gray squirrels were finding and invading the wooden feeder. I counted six that morning. I knew they were hungry too, but that day I was counting birds, not squirrels, for Project FeederWatch, a citizen science project of the Cornell University Laboratory of Ornithology, and the squirrels scared off the birds both intentionally and unintentionally. I, in turn, intentionally chased the squirrels.

Expecting the electric power to go at any minute, I worked in the kitchen all morning, baking coffee cake, making soup for lunch, and mixing and baking granola. But since our back kitchen door looks out at our bird feeders hanging from the back porch, I also was mesmerized by the birds at the feeders and on the ground, their comings and goings, the changing cast of characters, the alarm calls, the birds the others fled from, mostly blue jays and, to a lesser extent, the red-bellied woodpecker that swooped down like a bomber pilot and landed on the porch post, its rapier bill looking more threatening than it was. Common redpolls were more phlegmatic than the other finches, mourning doves more nervous, flying up at the least excuse in a sudden explosive rush that startled the rest of the birds. Tufted titmice and black-capped chickadees slipped into the feeders whenever the American goldfinches and house finches allowed them.  Although the northern cardinals arrived as a pair, the male pecked the female away from the food, a sure sign that he was in winter-survival mode and not ready to initiate courtship.

One of the red-bellied woodpeckers was actually orange-bellied as I noticed when it was on the ground, yet all the guides and articles I consulted, including the definitive Birds of North America, insist that their bellies are red.  The others I’ve seen are red, but this one was not.  Could it be the food it was eating?  After all, house finches can be orange and even yellow if they don’t eat red berries, because their diet determines their color.

By noontime rain splashed from the gutters and against the bow window.  Beads of water drops froze at the bottom edge of every branch as the thermometer stood at 30 degrees Fahrenheit.

Near sunset, the rain stopped, and Bruce and I crunched through the granular, snowy ice in the glittering forest with its tree branches dangling icy raindrops. And the feared electric outage?  Much ado about nothing.

The next morning, on Groundhog Day, Punxatawny Phil saw his shadow.  That seemed unlikely because at dawn it was 28 degrees and overcast.  In any case, we always have more than six weeks of winter still ahead of us on that date, regardless of what P.P. predicts.

By late afternoon, I stopped waiting for the promised sun and went out into an ice-shrouded world that glowed a faint pinkish-gray beneath a clearing sky.  A red-tailed hawk took off from the edge of First Field, and I followed it with my binoculars as it wove its way through the trees overhanging the field and finally settled on a tree branch halfway up Sapsucker Ridge.

Only tree branches had been pruned by the ice so I could appreciate the glassy, shining shell encasing every grass stem, sapling and tree branch.  The crust held the deer and me up as if it was a roughly-frozen lake.  Coyote Bench was white and overhung with saplings bowed by ice.  Fat tree trunks were hoary with ice, like scenes from C.S. Lewis’s Narnia in his book The Lion, the Witch, and the Wardrobe, where the White Witch ensures that it is always winter. Unlike the four children in that tale, though, who were caught in endless winter without proper clothing, I was dressed warmly and embraced the beauty of the ice instead of fearing it.

A large tree branch that had broken and fallen under the ice load, stood upright in the icy-snow on the Far Field Road. Shards of ice littered the road and crunched beneath my feet.  The spruce grove was frozen and dark, the trees bowed and anchored to the earth by ice.  Dark-eyed juncos and northern cardinals that had sought shelter within the evergreens chipped at me in the gathering dusk.

The following day, I still found a Narnia-frozen world along Greenbrier Trail.  Clouds moved across patches of blue sky on that soft, silvery, silent, Sunday morning.  Once I stopped my crunching walk and heard the clarion call of a hairy woodpecker, the whooshing of a flushing ruffed grouse, the calls of tufted titmice and northern cardinals, and, of course, the inevitable traffic noise from Interstate 99 below because of a strong inversion layer due to the heavy fog in the valley. Despite the weather, there was much toing and froing along the highway, and I wished that I could share the “beauty of the earth” and “the glory of the sky” on the mountain with those folks enclosed in their machines.

A soft mist hung over Laurel Ridge.  Along Greenbrier Trail on Sapsucker Ridge, every branch and berry shone in its glassy cocoon.  But when I ascended to the top of the ridge, every icy twig and branch bristled with hoarfrost.  The valleys were still wrapped in fog even as the sun began to emerge from the floating cloud cover and sent shadows over the snowy, ice-covered mountaintop.

Looking across at the end of Laurel Ridge, I could see the hoarfrost line reaching down only a hundred feet or so.  The ice glittered and glowed as the sun winked in and out.  Hoarfrost clung to patches of rough bark that stood out on the trunks of oak trees.  Prickles of hoarfrost even stuck to smooth-barked striped maples. Droplets of ice that hung from the undersides of many branches shone in the sunlight. But other icicles hanging from branches were also encased in hoarfrost.  Striped maple keys, enclosed in ice and outlined with hoarfrost, dangled from red or gold, hoarfrost-covered branches like shiny, beige Christmas ornaments. Hoarfrost even whitened the needles of pitch pine trees that overhung the ridge.

Mine were the only human prints on the trail, the cloven hoofs of deer the only animal tracks that were heavy enough to make an imprint like mine, or even to break through the ice.

At 10:30, as the sun shone more and more determinedly, a gray squirrel crossed the trail in front of me. Ice creaked in the treetops and shards crashed down as the temperature rose.  Ice-covered large tree trunks, patched with green lichens, and fallen trees, glistened in the thawing warmth.

I found a red-eyed vireo nest filled with snow, it’s outside a sheen of ice, anchored on a low-hanging red maple tree limb.  As the sun shone fully, I looked across at Sinking Valley, but all I could see were the tops of distant mountains, blue above the billowing white fog.

A shard of ice hit me on the back of the head, and I realized that a hard hat would have been in order.  A blue jay called in the distance.  As I crossed the powerline right-of-way, a portion of fog momentarily lifted, kaleidoscopically revealing what looked like a toy town below. Ice shrouded every rock along this section of the heavily-wooded trail. Mountain laurel leaves were bent and ice-shiny.

Black-capped chickadees sang and called in the spruce grove.  An American crow flapped quietly overhead as I descended First Field to the accompaniment of melting, dripping ice.  All the black locust tree trunks glowed lime green under their ice cover, lending color to the beige edges of the field.

Fog rolled up from the valley, briefly enveloping the area where I had walked.  A northern cardinal glowed red in an ice-covered multiflora rosebush.  Tufted titmice, a red-bellied woodpecker, downy woodpecker, white-breasted nuthatches, and black-capped chickadees called from the forest on either side of the field, invigorated by the melting warmth of a February thaw.

Within an hour, the glory was gone.  The sun shone warmly, and the temperature reached a brief 43 degrees before retreating to the thirties in late afternoon. And I was back to chasing squirrels from the feeders.