October

In this part of the world, everyone knows what October is about: it is the season for fall colors. Our forests are species-rich, and the leaves of the various trees turn different colors in their own time. This means that October offers an ever-shifting patchwork of yellow, orange, red, bronze, and brown. Neither the onset nor the duration of fall colors is predictable, but the order of leaf senescence is fairly reliable, with the black walnut first, and the birches and some oaks among the last. Disconcertingly, the parade of color is especially vivid and long-lasting in town, where the local trees are supplemented by ornamental cultivars and species that have been selected and bred for showy fall leaves and colorful berries. Add in the serried ranks of potted purple, yellow, red, and white “mums” (chrysanthemums) for sale at every grocery store and gas station, and October is a kaleidoscope of color. Meanwhile, the hard business of earning a living in the natural world goes on. Squirrels, chipmunks, and other small mammals are stocking up before the winter begins in earnest; the last butterflies and honeybees of the year forage valiantly for nectar on any day with a shred of warm sunshine; and many birds are on the move to warmer climes.

Two of this month’s essays explore the lives of birds. The first examines the strange business of late-season birdsong, focusing mainly on a resident, the Carolina wren (“Autumnal Songsters”), and the third essay considers one of the migrants, the orange-crowned warbler, which passes through at this time of year (“A Relocating Crown”). Trees figure large in the other essays. I consider the black walnut tree, whose fruit is harvested avidly by squirrels (“Black Walnut Bonanza”), and I finish with some thoughts on the ever-changing forest landscape in our region (“In the Carbon Sink”).

Autumnal Songsters

We are moving inexorably away from summer and toward winter. The squirrels are endlessly burying black walnuts and other goodies in our lawn, the leaves of our red maple have a reddish tinge, and I have been busy sweeping up box elder leaves from the driveway. The crickets are still with us, but their singing is getting ever fainter. By day, the main sounds are the tooth chattering of squirrels . . . and the song of the Carolina wren.

The full song of the Carolina wren reverberates around our backyard. A wonderful three-note pidaroo, pidaroo, pidaroo is repeated very quickly over two or three seconds, then silence, then back to pidaroo or interspersed with a frantic buzz. These sounds feel out of place. They belong to the spring, when the birds are disputing nesting territories and impressing their lady loves, before they are overwhelmed by the hard and mostly silent labor of parenting. Now that the young are fledged and parental responsibilities are done, the male Carolina has returned to his blazing song.

One type of explanation belongs to the “can’t help it” category. In early spring, long before the temperatures rise, our local birds respond to the rapidly increasing day length by producing lots of testosterone. This potent hormone compels them to sing loudly, fight off intruders, and court females with great fervor. Birds detect the lengthening days not through their eyes but via a light detector, called the ventromedial hypothalamus, deep in their brain. This tangle of nerve cells contains a pigment called the vertebrate ancient opsin—or VA opsin for short. The opsins are a remarkable family of proteins that change shape depending on whether it is light or dark. The best-known opsins are in the eyes of birds and mammals, including humans, and they are used for seeing. The VA opsin functions differently. It calculates day length from the period in every twenty-four hours that light filters through the very thin bird skull and outer brain tissues to the ventromedial hypothalamus. What’s more, this birdy molecular calendar is wired to trigger a cascade of downstream changes in the brain when the time is right, resulting in the overwhelming testosterone surge.

This argument claims that the bird brain calendar has its limitations. It responds to rapid changes in day length, whether it’s increasing or decreasing, causing the ventromedial hypothalamus to tell the bird’s body that it is time to breed as we pass the late September equinox. The bird starts to get all testosterone-y and starts to sing. Other cues, such as declining temperature, protect the bird from being too stupid, starting to build a nest, for example. (Digressing briefly, bright streetlights and other artificial lights are bad for birds because the extra light confuses the VA opsin in the ventromedial hypothalamus, telling them that the season is more summery than it really is.)

There is increasing evidence that this “can’t help it” argument may not be the total explanation. The interspersing of song and the buzz-like calls we hear is usually not the male mixing and matching, but male-and-female duetting. He sings pidaroo, pidaroo, pidaroo, and she responds with a zzzzzzzzzzzzzzzzzzz. They are telling each other that the kids are off their hands (or wings, perhaps) and it’s all still good. They can hang out together through the winter. The duet is also alerting potential interlopers that this backyard and this female are not up for grabs.

It is very possible that some of the singing at the end of the season can be attributed to juvenile males from the last brood. Apparently, Carolina wrens learn their song from their father, possibly starting lessons even before they are born. They begin to sing when they are about two weeks old. This is when they fledge. Carolina wren nestlings develop very quickly, fueled by all those spiders and caterpillars, but their first singing attempts are so pathetic that birders call it “subsong.” The youngsters hang around in their parents’ territory for up to another four weeks, presumably being very adolescent and annoying, but this behavior does give the youngsters more opportunities to hear Dad sing. Certainly, by the time the young males disperse from their parents’ territory, they are fairly good at the real song. It should be possible to distinguish junior from senior, though, because junior is careful to intersperse his pidaroos with the occasional pi-zeet, which is Carolina wren-ese for “I’m backing off; you’re bigger and better than me.”

I am pretty sure that all the offspring from the last brood have already dispersed from our backyard. Some of this year’s birds may even have bonded with youngsters from other nests, and those new pairs have started wandering around looking for a place to call their own—in other words, somewhere not already occupied by Carolina wrens. Other birds may have sounded or looked good to a recently widowed Carolina of the opposite sex who already has a territory. I guess that, in the Carolina wren world, this is striking it lucky.

The Carolinas are not the only birds with a song to sing in early October. The song sparrows are also in full voice. As with Carolina wrens, the resident song sparrows maintain their territory through the winter, and they are busy marking the boundaries with music. Other autumnal songsters have different things on their minds. The males of the house sparrows and the American robins are bellowing out their superior status to the winter flock, ensuring their preferential access to the next patch of food and their position at the center of the huddle when the first snowstorm comes, as it surely will.

I suspect that much more scientific research will be needed to understand fully why some birds sing in October, but I am sure that the answer is complicated. We should not look for a single explanation for the habits and behavior of wild creatures.

Black Walnut Bonanza

We have enjoyed several days of brilliant sunshine in this second week of October, along with clear nighttime skies. These conditions have driven us to search for our winter blankets and, more importantly, they have brought on the start of the fall colors. Pride of place goes to the black walnut tree, with foliage that has gradually shifted from pale green to lemon yellow as the week has progressed.

Every now and again, a black walnut leaf twirls gently down to the lawn in the crisp air. Then the peaceful, autumnal scene is disturbed by the loud thump of a heavy object falling from high in the tree to the ground. It is one of the tree’s many black walnut fruits from this year’s bumper crop. Each fruit is about two inches in diameter, the same weight as a small apple, and bright green until it darkens to a dull brown, which is caused by bruising from the thump and general wear and tear on the ground. Other fruits are denied the opportunity to end their days with a big crash followed by decay. That’s thanks to another disturbance: an incessant rustling in the tree. The local gray squirrels are chasing around the branches and checking the fruits. When a suitable one is identified, the squirrel clutches it in the forelegs, snips it off the branch with its sharp teeth, and maneuvers the great bulk toward its mouth. Somehow, the squirrel can then dash along the branch and down the trunk to the ground, its enormous booty held securely in its jaws.

Getting to the ground is only the end of Act One. Then comes the big decision: Bury the fruit or eat it? There’s plenty of space for burials on the lawn and in the flowerbeds. Our backyard is peppered liberally with squirrel scrabblings and walnut interments. Those buried walnut fruits will come in very handy during the harsh winter to come. Of course, the preferred outcome for the tree is for the squirrels to ignore the carefully concealed fruits, which need a long winter of subterranean damp and cold to germinate. If the gray squirrels left all their buried walnuts (that won’t happen!), our backyard would be jungle of black walnut seedlings next spring.

Far worse for the tree is the alternative and frequent choice of the squirrel. All too often, the squirrel succumbs to temptation and consumes the walnut, here and now. Hungry or imprudent, the squirrel rushes to an open spot, where it can keep an eagle eye out for the approach of a greedy friend or relation. Then it swiftly tears the shell apart with its teeth. This noisy business, a bit like the loud crinkling of aluminum foil being scrunched up, can be heard again and again through the day. The hard, brown nut at the center is a substantial and energy-rich snack, and it is hastily consumed. Satisfied, the squirrel scampers off to climb back up the walnut tree. All that is left is a small pile of bright green walnut shell chippings. Over the following days, these fragments will turn brown and soggy and ooze a purplish liquid. Our backyard is littered with these neat little piles on the lawn, the deck, and the driveway. And there are many more mounds of discarded black walnut shells here and there at various stages of decay on the roads and sidewalks in our quiet neighborhood.

It’s worthwhile to spare a moment’s thought for the jaws of the gray squirrel at this time of year. The hinge-like joint connecting its lower jaw to its skull must be stretched to its limit every time the squirrel carries the large and heavy fruit. What’s more, the force applied through the squirrel’s jaws and teeth in order to break open the walnuts must be immense. Humans need a hammer to get into them. An alternative strategy for harvesting black walnuts is to leave the fruit in a bucket until they get mushy, at which point the shells just slip off. If you try this, be sure to wear strong, waterproof gloves; otherwise, your hands will be stained a deep blue-brown. Meanwhile, the squirrels have sore jaws, discolored teeth and paws, and a good stock of food for the winter.

Let us return to the black walnut tree because it is not only the gray squirrels that are causing a rustling in the foliage. The red squirrel is also very much in town. Earlier in the week, we watched several reds chase one another up, down, and around, all at great speed. Most likely, they were youngsters preoccupied with the tasks of playing and mock fighting. Unlike the gray squirrels, who continue the complexities of social interactions throughout their lives, this activity is short-lived for the reds. We haven’t seen them in the last couple of days, and I suspect that the youngsters have gone their separate ways to stake out their individual territories. All in all, most adult red squirrels lead lives of near-monastic isolation in fiercely defended territories. There are exceptions, though. A female allows males into her territory for a single day during early spring and again at midsummer, before shooing them away so she can raise her two litters alone. And in some rich habitats with plenty of food, the territories become porous and overlapping, although individual squirrels continue to avoid direct contact. Our observations over the years suggest that the conditions in our backyard favor strict territories.

The female red squirrel that owns our backyard is very busy. Her preoccupation is black walnuts, not her offspring. She careers around the tree, then nips off a suitable fruit, letting it fall to the ground. Then she races down and manhandles the great fruit back to her larder, located in the narrow strip between our garage and the garden fence.

When we checked the red squirrel larder earlier today, there were more than a hundred black walnut fruits, together with some spruce cones. The squirrel must have spotted us because she came racing down the spruce tree, chattering fiercely. We backed away to demonstrate that we had no designs on her hoard. Life is neither easy nor placid for the red squirrel, but if she can protect her store, then she will be set up for the winter.

A Relocating Crown

I am not writing about a worrying dental problem but a much more interesting and decidedly mobile crown in Allan H. Treman State Marine Park at the southern end of Cayuga Lake.

It was early on Sunday morning, and we had the trail almost to ourselves. As we swished our way over a carpet of yellow, brown, and red leaves in brilliant October sunshine, we passed solitary song sparrows singing out the boundary of their territories every hundred yards or so, and we heard the loud caroling of the occasional Carolina wren. It was calm at the lakeshore, and the narrow concrete spit extending from Lighthouse Point to the Cayuga Inlet Lighthouse bore a long line of birds: many double-crested cormorants, together with ring-billed, herring, and black-backed gulls. The gulls will stay with us all winter, but we anticipate that the cormorants will be departing for warmer climes before long.

But then there was a surprise. Near one of the song sparrows, another bird was flitting in the bushes. It was definitely small and decidedly nondescript, apart from a bright yellow patch under its tail. Its breast was perhaps a little streaky (it was difficult to be sure), and its beak was narrow and pointed. It was definitely a warbler, presumably taking a break on its journey south. A quick check through our bird book showed that only one species sports a bright yellow bottom: the orange-crowned warbler or, more colloquially, the orange-crown.

A little more detective work was needed to work out where our orange-crown had come from and where it was going. The summertime distribution of the orange-crown is like an upside-down L, extending across the midlatitudes of Canada and Alaska and down the west coast of North America, inland as far as the Rocky Mountains. It’s a bit more complicated than that because there are four subspecies of orange-crowns. Our bird was almost certainly sub-species celata, the most drab of the orange-crowns. Our little celata could have flown straight down from northern Québec or it could have come across from Alaska on its way to Florida, the Mississippi Delta in Louisiana, or Mexico.

Orange-crowns almost always travel by night and are usually alone, but they will occasionally travel in small groups. As with the many other birds that migrate under cover of darkness, orange-crowns navigate using the stars. More specifically, they use the North Star: the one star that is stationary in the sky all night. The constellation of Orion is also useful because its apparent position shifts little as Earth rotates. Stargazing is a great way to navigate on a clear night, but it’s not so smart when it is cloudy. Nevertheless, our little birds can keep going, thanks to a second navigational system that is weather-independent; they can make use of Earth’s magnetic field. I am pretty sure this hasn’t been studied in orange-crowns, but other warblers, notably the European reed warbler, have tiny, iron-rich crystals of magnetite close to their nares (you could say in the nose). Any change in intensity and possibly direction of the magnetic field is communicated from these crystals to sensory nerve endings associated with the nares and beak, and the nerve impulses are transferred, in an instant, to the brain. Presto! The bird has information on where it is and where it is going.

So much darned cleverness has to be learned by the youngsters while sitting in the nest at the bottom of a scrubby bush in the forest—and during the short period between fledging and the four thousand–mile journey south: how to fly; how to find all those scrumptious beetles, caterpillars, and spiders; how to avoid the local hawks and any cats in the neighborhood; and how to recognize and, for the boys, reproduce the sweet, trilling song. On top of all that, they also have to learn how to read the stars. I suspect that interpreting the electromagnetic field generated as Earth’s molten iron core swirls around is hardwired in their little warbler brains. It’s a crash course for survival during their first two or three months of life.

There’s one more important issue to address about the little orange-crown that was hopping about in the bush last Sunday morning: Why is this ultimate LBJ (an honorary little brown job that is in fact gray) called an orange-crown? Almost none of the pictures and photos of the bird display brilliant orange headgear. Exceptionally, the entry for this species on the Cornell Laboratory of Ornithology (n.d.) website (All about Birds) has a photo of a male turning its head to the camera and displaying a diminutive pale orange patch on the top of its head. The accompanying text informs us that the orange patch can become evident when the bird is excited or agitated, but it is not usually visible.

I strongly suspect that the bird was named from a dead specimen, either shot or trapped, allowing detailed inspection of the diminutive orange patch. The authority was Thomas Say (1787–1834), whom I have encountered before as the much-lauded father of American entomology. Say was an intrepid explorer who identified and named the orange-crown while on an official expedition to the Rocky Mountains in 1819–20. He was also something of an idealist. In 1826, he was one of several hundred who joined the New Harmony settlement in Illinois with the dream of jump-starting a new moral world. Of course, the settlement collapsed in quarreling unhappiness by the end of the decade, but Say didn’t get involved with the inharmonious infighting. Instead, he focused on his natural history studies, including preparing his groundbreaking three-volume treatise on American entomology. He stuck around in New Harmony, even though the utopian settlement had dissolved, pursuing his natural history studies, until he succumbed during an outbreak of typhoid fever in 1834.

Meanwhile, the inappropriately named orange-crown today flourishes with the conservation status of least concern. There is nothing better for the orange-crowns than all that shrubby under-story that grows up after logging and is then left alone (thanks to the no-fire management policies of the last century).

Nevertheless, there is no place for complacency when it comes to the orange-crowns. There are many ongoing changes in the landscapes where these birds breed. Forest management practices are shifting to favor elimination of the highly flammable bushy under-growth where they nest, and the increasing incidence of intense wildfires and heat waves in the west are taking their toll. The prognosis for very few species can be assured in our rapidly changing world.

In the Carbon Sink

The area around Ringwood Ponds is a pleasure to visit in the fall. The trails weave through mature maple, birch, oak, and hemlock trees, with saplings of all sorts in the understory. Dead tree snags are riddled with woodpecker and insect holes, and windthrown trunks lie untouched on the forest floor, supporting a world of wood-decay fungi of various colors and shapes. Newly fallen leaves litter the ground, chipmunks and squirrels scamper around, and blue jays call from the upper canopy. It is a magical place with a timeless feel to it.

But this landscape is far from timeless. It is obvious from the terrain that it hasn’t always been like this. The trail takes us along eskers, ridges of now well-stabilized sediment that was deposited by the Wisconsin ice sheet as it receded between ten and twelve thousand years ago. The dips on either side of the eskers form temporary ponds that usually dry up in the summer and are reformed with snowmelt each spring. Another unambiguous sign of the past ice ages are the several kettle holes: round depressions scoured out by a block of glacier ice that became covered in sediment and then melted. These kettle holes gave the place its name: Ringwood Ponds. Amphibians love the site for its ponds and swamps, and the Big Amphibian Courtship Concert takes place at Ringwood Ponds every spring (see April, “Spring Peepers”).

As the ice sheet and glaciers receded, the barren land was colonized by plants and animals, ultimately leading to forests. I wish I could add that our old-growth forest is the direct descendant of those first postglacial forests, but there is a complication. That complication crossed the Bering Strait from southern Siberia to North America between eleven and twelve thousand years ago, and it then reproduced and dispersed, eventually reaching what is now New York State about nine thousand years ago. I am writing about humans.

These humans gave rise to the Indigenous peoples of North and South America. In our region, they engineered the landscape with fire. Regular, purposeful burning of the forests killed fire-sensitive trees and the understory, leaving a park of magnificent trees with thick, fire-resistant bark. These trees were mostly nut-producing red oak, shagbark hickory, and sweet chestnut, along with pine and hemlock. There was no need to bushwack your way through undergrowth when hunting for deer, and the groves of nut trees supplemented the corn and bean crops grown in small clearings. It appears that this type of landscape engineering was sustainable and supported relatively large human populations. In the first written records kept by Europeans in North America, the land in this area was occupied by the Gayogohó:nǫ^? (pronounced Guy-yo-KO-no), which means “from the swampy land” (Jordan 2022).

There are a few very steep and inaccessible places in the local region where the mix of tree species is best explained by human engineering that predates European settlement, but Ringwood Ponds is certainly not one of them. To understand Ringwood Ponds, we must consider the complications of human history. European colonists did not settle in our patch of New York State until after the American Revolutionary War (1775–1783). The local Indigenous people had backed the wrong side (the Brits) during the war. As retribution, they were driven out, and the land was given, in ten-acre packets, to veteran American soldiers. In the eyes of most Americans, Indigenous people had no legal ownership of the land because they did not enclose it. The white settlers chopped down the forests to farm crops and establish sheep pastures. These ventures were ultimately unsustainable because the soil, scoured by glaciers, was poor and the agricultural methods were primitive. Within a few generations, residents started to move to the western frontier, meaning the rich river basins of Ohio, and then even farther west. The abandoned farmland in New York gradually reverted to forest. Fragments of stone walls, which had been built to enclose sheep, and the foundations of cottages are evident all over the place in the forest.

The forest at Ringwood Ponds is designated as old growth because it has not been logged since the 1860s. Much of the forest in this area is more recent than that, including trees that have grown back over farms that were abandoned well into the twentieth century.

This brings me to the carbon sink of my title. The forests of New York State and New England represent an important sink for the carbon dioxide in the air. As the trees grow back over old agricultural land, they suck in carbon dioxide, trapping the carbon in wood that is laid down as they grow. However, as we see in the old-growth forest at Ringwood Ponds, trees eventually die and their wood is consumed by fungi and insects, converting much of that carbon back to carbon dioxide. There is excellent evidence that the amount of carbon dioxide New York State forests are gobbling up (in other words, the strength of the carbon sink) is declining because the forests are maturing with increasing numbers of dead and decaying trees.

What this means is that New York State is a strong carbon sink not because it has lots of forest but because much of that forest is young and actively growing. What’s more, our forests are merely recouping carbon lost from the land by deforestation over the last few centuries. It is sobering to think how the consequences of how we manage the land takes effect over very long periods of time—often longer than we can readily comprehend.