Anyone who’s ever spent time walking through Northeastern wetlands in late winter is familiar with skunk cabbage (Symplocarpus foetidus), one of the earliest flowering plants to appear each year. To this lover of spring, its appearance feels like a joyous harbinger of the glories to come.

Even so, I’ve never paid much attention to the plant itself. It wasn’t until I took a walk recently among the swamps, streams, and wet forests of Pruyn Sanctuary and spotted the purple-and-white foliage emerging through patches of snow and ice that a simple question occurred to me for the first time.

How does the skunk cabbage do it?

Or, more specifically: What enables it to be first, growing so luxuriantly when most plants have barely begun to produce their first buds? The answer—as so often with the natural world when we look at it closely—is fascinating, even astonishing.

Symplocarpus foetidus, it turns out, doesn’t emerge earlier than most other wildflowers because of extra-tough leaves, some kind of antifreeze in its veins, or sheer force of will. It erupts through the snow and ice because, unlike any other plant in our region, it carries its own heating system. It actually functions like (for want of a better term) a warm-blooded plant during those cold late-winter days.

The skunk cabbage generates heat through the process known as thermogenesis, which in fact closely resembles the process used by mammals and other warm-blooded creatures. The process begins with starches the plant has stored in its roots and rhizome (the part of the stem that lies underground), all in preparation for the slightly less cold days of late winter.

Often weeks before most other plants are active, the starches begin to break down, a process that produces a significant amount of energy—i.e., heat. It then exudes the heat through its pores (called stomata) in a process called cellular respiration.

Scientists have found that, over the short term (usually a week or two), a skunk-cabbage plant can warm itself and the earth around it dozens of degrees above the temperature of the surrounding air. In addition, this little engine warms the nearby soil, making it more hospitable to the plant’s growth.

In researching this piece, I discovered that the skunk cabbage wasn’t through surprising me. I’d always assumed that the glossy, mottled purple-and-white shoots that emerge first are leaves. They’re actually leaf-like structures called spathes, which enclose spike-like stems called spadices. (Singular: spadix.) The plant’s abundant clusters of yellowish flowers grow on its spadix, and the leaves—a less glossy green—appear later.

As so often, the answers to some questions about the world around us only lead to more. For example: Given that the skunk cabbage’s flowers are pollinated by insects, are there enough bugs around in late winter to do the job?

There are, in fact, insects that hatch out at the same time that the cabbage blooms, including its pollinators, flies, stoneflies, and bees. By sending out its flower spike so early, the skunk cabbage is functioning as a classic “early bird.”

The plant’s skunkish odor—most noticeable up close—may also help the plant attract its pollinators, many of which typically feast on carrion and rotting vegetation along with nectar. Even in a season where there may be few insects about, the cabbage makes its presence known to the ones that have hatched.

Even the skunk cabbage’s temporary “warm-bloodedness” plays a part in its ability to thrive under challenging conditions. As well as giving the plant a jumpstart on spring, its self-generated heat may help its insect-attracting odor spread more widely through the air. And once the pollinators approach, the greater warmth within the spathe tempts them inside, where the flowers—and pollen—are.

My walk in Pruyn Sanctuary inspired me to learn about this unique native plant. Even so, for me the best thing about seeing its early leaves—I mean spathes—emerging from the winter earth hasn’t changed at all. To me, the early emergence of skunk cabbage will always mean one thing: Spring is coming. Copyright © 2020 by Joseph Wallace

I admit it: I take Black-capped Chickadees for granted. I mean, I like them: They’re cute, a dependable and confiding visitor to feeders, and one of the few birds that may actually fly over when I show off my “pishing” birdcall to skeptical friends. Even so, to me at least they’ve always been more Old Reliable than Must See.

But it turns out that, as with most things, we miss a lot when we underestimate chickadees. These familiar little birds have much to teach us about taxonomy, speciation, even the evolutionary roots of birds’ learning ability.

Currently, seven chickadee species are recognized in North America, ranging from the Mexican, which enters the U.S. almost entirely in the Sky Island mountains of Southeastern Arizona, to the Grey-headed, found only in Northwestern Canada and Alaska. Almost every spot in between has a chickadee species as well…though rarely more than one.

In divvying up the continent in this way, chickadees provide a vivid example of what Charles Darwin first demonstrated with the famous Galapagos finches and mockingbirds: How even subtle differences in geography, altitude, and food sources—like those found between New York with its Black-cappeds and Washington, D.C., where Carolinas are the rule—can cause a common ancestor to split into several different species.

Yet how split these species are remains an intriguingly open question. As a glance at a bird guide shows, the different chickadees all remain so closely related that they resemble those old “find seven differences between the two drawings” puzzles. (The Carolina Chickadee is only slightly smaller than the Black-capped; the Boreal has a brown instead of black cap; the Mountain Chickadee’s “chick-a-dee” call is a little harsher and faster than the Black-capped’s, and so on.)

Clearly these little apples haven’t yet fallen far from the family tree. But the real question is: Have they fallen at all? Because, confoundingly, in the small areas where Carolina and the Black-capped Chickadees overlap (a narrow zone running from Kansas east to New Jersey), it turns out that they interbreed freely…and produce plenty of fertile offspring.

Given that our longtime definition of “species” centers on the ability to produce fertile young, does this make Carolina and Black-capped the same species? And if so, how about their cousins, who appear no more distantly related? Could we actually be looking at a single superspecies?  

These are all good questions, though not ones that birders who keep life lists might want to hear. They’re also the same questions that are now being asked about many other bird and animal species long considered separate. (Perhaps most remarkably, polar and grizzly bears turn out to be able to produce fertile offspring, a finding that feels like a harbinger for the future as climate change brings species previously isolated by distance into close proximity.)

But chickadees do more than intrigue genealogists. They’ve also caught the attention of those who study communication—even among different species.

For many small songbirds, “mobbing”—and thus calling attention to—raptors and other potential threats serves as a survival technique. Around here, Black-capped Chickadees often lead the mob, their emphatic “chicka-dee-dee-dee!” calls serving as the first sign that a hawk or owl is in the vicinity.

Their mode of communication is more complex than that, though: The birds actually signal the seriousness of the threat. The greater the danger, the more “dees” the bird appends to the original “chicka.”

When the threat is dire indeed—as with songbird-hunting owls—the chickadee may sound off with more than a twenty loud “dees.” The intensity of the calls can serve as either a warning to hide or a summons to join the mob, dictates that both fellow chickadees and other species (such as nuthatches and Downy Woodpeckers) understand and take heed of.

Chickadees have even more to teach us. How they’ve evolved to ride out northern winters is, in fact, the tale of one of the most remarkable evolutionary adaptations in the animal world.

In spring and summer, chickadees are like many other birds, eating a mix of vegetable matter (mainly seeds) and insects. Unlike most songbirds, though, they don’t migrate to warmer climes in winter. Instead, they remain reliant almost entirely on seeds left over from the growing season, a food source that may be abundant one day, inaccessible or gone the next.

To survive these realities, chickadees have evolved the ability to cache seeds, hiding them in many different locations. Sometimes a single bird will cache seeds in more than a thousand different spots.

Caches provide certain food stores, no matter the weather, and using many sites guarantees that another opportunistic seed-eater won’t discover and plunder a chickadee’s entire supply. But this remarkable survival technique provokes a question: How do chickadees find all their hiding places? How do they remember?

The answer is that they rely on their hippocampus, an area of the brain responsible for spatial organization. Simply put, it’s the part that enables them to recognize and identify where they left something.

In many species, including humans, the hippocampus serves this same function. But most of us don’t have to remember a thousand different knotholes or patches of loose bark, much less as a requirement of survival. (Simply recalling where we left the car keys is challenging enough.)

So how do the birds accomplish this herculean task? Through a remarkable evolutionary adaptation: Each year in the fall, as the chickadee gathers its trove, its hippocampus grows as much as 30 percent. It is, in effect, making room for the new memories it will need to endure the winter.

Then in the spring, as abundant new food sources appear and an unerring spatial memory is no longer such a high priority, the chickadee’s hippocampus will shrink down to its previous size. Until the next fall, when the process will repeat.

As I’ve been writing this, a chickadee has been making regular visits to the feeder out my back window. Now, as I watch it fly off in different directions with one safflower seed at a time, I know why. I’m also reminded of something deeper, more essential, about the world around us: Even in small, familiar, and—yes—adorable packages, it remains full of surprise, wonder, and unexpected new knowledge. © 2020 by Joseph Wallace

You don’t have to be a birder to notice the huge flocks—sometimes numbering 100 or more—of big, dark birds looming over downtown Croton-on-Hudson this fall and winter. Or to know what they are: vultures (often nicknamed “carrion crows” or “buzzards”), those notorious scavengers of road kill and other carcasses that seem to be increasing in number every year around these parts.

Their growing presence is all a glance will tell you about the local vultures, and for many people, that’s all they need to know. But—as with so much in the natural world—if you take a moment to look closer, you’ll see that the story of these big birds is far more complicated, full of surprising twists and turns.

First of all, Croton doesn’t simply have “vultures”: It has two different kinds, Turkey and Black. They’re actually pretty easy to tell apart. The more common TVs, brown-black in plumage, have long wings that slant upwards, forming a V, as they tilt buoyantly in even a slight breeze. BVs, a more recent arrival in our area, are darker (with silver-white patches at their wingtips), slightly smaller and squatter, and have a heavier flight. They flap much more frequently than their cousins.

And while they both have bare, featherless heads, Turkey Vultures’ are pink and Black Vultures’ grey-black. (Bare heads make for less mess when they’re delving deep in a carcass for succulent morsels—and aren’t you glad you know that now?)

But there are other, more fascinating differences between the species. Turns out they also boast dramatically different behavior, feeding habits, and dominance.

For example: Even though we see the two species soaring and roosting together, they don’t actually get along that well. Since Turkey Vultures are larger on average, a single individual can dominate a single Black at a feeding site. But Black Vultures have a way to counteract that size disadvantage: They team up. They form a pack…and a pack of BVs can almost always drive a lesser number of TVs away.

Secondly, while Turkey Vultures depend almost entirely on carcasses for their food (only rarely killing a sick or young animal), Black Vultures hunt live prey much more frequently. The pack mentality, more akin to wolves or lions than other birds, even allows them to bring down mammals such as skunks, calves, and young pigs.

But perhaps the most striking difference between the two species is that they use two entirely different senses to locate carrion.

Black Vultures, like most day-flying predatory birds, rely on their keen eyesight. When foraging or hunting, they soar (and flap) high in the sky, scanning the ground below.

Turkey Vultures, however, use a far rarer—almost unheard-of—method: They employ their sense of smell. Recent research has shown that the vultures possess an olfactory bulb (an area of the brain that processes odors) far larger than that of Black Vultures. In fact, their olfactory bulbs are larger as a proportion of brain volume than those of nearly 150 other bird species studied.

This and other anatomical differences allow Turkey Vultures to recognize ethyl mercaptan, a chemical produced when a dead mammal has begun to decay. The vultures can detect this chemical sooner after death than any other carrion-eater, making them most often the first to the feast.

The same adaptations mean that foraging Turkey Vultures tend to fly low over the canopy, which gives them a better chance of catching that first whiff of ethyl mercaptan. And the Black Vultures? While they soar higher, scanning the ground with their keen eyes, they’re also keeping a close eye on their cousins flying closer to the ground. When a Turkey Vulture locates the carcass first and descends, down swoop the BVs as well. (And then sometimes attack in a pack to drive away the bird that first located the meal.)

Perched on their rooftops and tree limbs, Croton’s carrion crows seem little more than a group of silent, hulking nuisances. But like almost everything in nature, they actually paint an extraordinary portrait of adaptation, competition, and survival. One that rewards a closer look.

Joe Wallace