Every year, there’s a certain day when I finally believe that spring is coming. It’s not necessarily on March 20^th or 21^st, whenever the calendar decrees the season has arrived. Nor is it that first warm day after a long winter, the time I spot the first hardy crocus, or even the first dawn that’s greeted by the songs of Robins, Cardinals, and other birds that have been silent—or absent—all winter.

No…that day comes the first time I walk in a local park and hear the Pinkletinks calling.

Or, as we know them, Spring Peepers (Pseudacris crucifer), the minuscule frogs whose calls fill the late-winter woods in our area. “Pinkletink” is what they’re affectionately known as on Martha’s Vineyard. (I suggest we appropriate this glorious name.)

The rhythmic, high-pitched Peeper chorus begins as early as late February in the Northeast, even before the skunk cabbage sends out its first shoots. It emanates from the hundreds of frogs that can gather in small ponds (frequently temporary ones created by melting ice and snow) and other wetlands. Here males call for mates, vying for the females who will choose them.

While I’ve enjoyed this chorus for many years, it wasn’t till this spring that I began to wonder: How can these tiny creatures be out and about when the snow has barely left the ground and temperatures at night still frequently fall below zero? After all, they’re as cold-blooded as any other amphibian and reptile, most of which don’t emerge till much later.

The answer is antifreeze. Like overwintering insects and seeds, Peepers produce chemicals called cryoprotectants—often glucose and glycerol, the same chemical we use to keep our cars from freezing. They allow the frogs to survive in leaf litter or under loose bark during the coldest months and become active again as soon as the weather thaws.

You might be able to spot a recently emerged Spring Peeper as it makes its way to a nearby pond. But you’d better have sharp eyes: Peepers reach no more than an inch and a half in length and weigh in at between a tenth and a fifth of an ounce. They’re brown or tan with a darker cross- or x-pattern on their backs. (It’s the cross that gives this species, its scientific name; crucifer means “cross-bearer.”)

Once the males reach a pond, they carve out a tiny territory and begin to sing. The result may seem like an undifferentiated wall of sound to us, but it’s actually just one part of a fascinating process.

Nearly always, three frogs whose territories adjoin sing in competition. The one with the deepest voice usually begins a round of calls, and the one with the loudest, most persistent sound (not always the same individual) is most likely to attract a female.

Yet this “survival of the loudest” process comes with one major complication: The territories of singing males are haunted by “satellite males.” These individuals don’t sing at all; instead, they hang around the periphery of the other males’ territories, hoping to intercept—and force themselves upon—females as they hop in to choose their mates. As many as 15% of all the males in an assemblage may be satellites, and they often succeed in their goal.

Studies have shown that these silent males are often smaller and less robust than the males they preempt. Therefore, they’d rarely be a female’s choice. Yet this widespread behavior seems to offer the whole species a surprising evolutionary benefit.

Spring Peeper populations have ebbed and flowed during the series of Ice Ages that swept across northern North America over the past two million years. At the depths of the freezes, the surviving populations have often become isolated from each other, sometimes for thousands of years. During these long separations, the species split into several different lineages, which scientists have been able to identify through DNA analysis.

With the retreat of the most recent Ice Age (about 18,000 years ago), separate Peeper lineages rejoined each other. These populations hadn’t diverged enough to form separate species, but even now they often feature significant differences in size and voice. Researchers have found that satellite males often originate from a different lineage than the predominant one in their area. Meanwhile, females prefer to stick with the males from their own original population.

When a smaller satellite male takes the place of the stronger one a female would have chosen, it would seem to directly challenge the evolutionary philosophy of “survival of the fittest.” The result, however, may bring greater diversity and strength to the species as a whole. Simply by increasing the gene pool, this mixing of lineages can help reduce the risk of harmful mutations, increased susceptibility to disease, and other threats common in populations that are inbred.

Regardless of her mate, a fertilized female typically produces about 900 eggs in a single clutch. These are hidden amid vegetation and leaf litter at the bottom of the pond, where they hatch in 6 to 12 days. Surprisingly, the tadpoles then take an unusually long time (as much as three months) before maturing into frogs. Every year, vast number of young Peepers perish when their temporary ponds dry up.

Even so—and despite the ongoing wetland pollution and development that have reduced their population in some places—Spring Peepers remain a common species in undisturbed and regenerating woodlands throughout our region. As long as we continue to give them the space they need, our noisy Pinkletinks should serve as an unmistakable harbinger of spring for a long time to come.

Copyright © 2021

By Joseph Wallace

My wife and I were walking along a familiar path in Rockefeller State Park when we glimpsed a sudden movement at the edge of the trail. A small animal, something quick, agile, and unpredictable, dashing around on the forest floor so quickly it was hard to focus on.

What on earth was it? My brain cycled quickly through the possibilities. Not a mouse, mole, vole, or rat. Maybe a Red Squirrel? No: Aside from the size, the little creature at our feet—pausing for a moment to stand on its hind legs and glare at us, showing off its white belly—was all wrong for a squirrel.

Then the animal dove into a pile of brush, and its speed and strange, almost snakelike motion revealed the answer. It was a Short-tailed Weasel, just one of six members of the family Mustelidae native to New York. Its local cousins, the Long-tailed Weasel, American Marten, Fisher, American Mink, and North American River Otter, can also all be seen in the Hudson Valley.

Can be seen, but rarely are. With the exception of water-loving River Otters, which sometimes appear—as if out of nowhere—in bold family groups in the Hudson River and the region’s lakes and reservoirs, mustelids are often extraordinarily wary. Weasels, Martens, and Fishers tend to stick to dense woods, while Mink prefer the forested edges of remote ponds. The truth is, if you’ve spent any time in the woods, you’ve likely been observed by many more mustelids than you’ve ever glimpsed.

Mustelids are native to every continent but Australia and Antarctica. Unlike the species in our region, members of the family can be found in a wide variety of habitats: Badgers, for example, prefer grasslands, Wolverines the frozen tundra, and aquatic Sea Otters the kelp forests of the Pacific Ocean.

Regardless of their habitat, though, nearly all mustelids share some essential characteristics, the ones we saw during our brief weasel encounter. Most are quick, agile, aggressive, and absolutely fearless. Together, these attributes make them peerless hunters, pound for pound (or ounce for ounce) among the fiercest of all carnivores.  

Much else about mustelids’ life story remains little known, however. They are hard to find and hard to study. Even radio collars (a go-to for field researchers hoping to follow elusive species in the wild) don’t usually work on weasels and other small members of the family. The problem: the animals’ extraordinarily supple bodies allow them to wriggle easily out of the collars.

Scientists do know, however, that the animals’ relentless energy requires constant refueling. Weasels’ metabolism is extravagantly demanding (their hearts beat at an astonishing 350-400 beats per minute), which means that each day a single individual must consume a third to half its body weight in food.

This constant need for fuel means that weasels can’t wait patiently to ambush their prey, as most wild cats do—doing so would take too much time. Nor can they pursue their prey until it slows or drops from exhaustion (a method often used by wolves and other wild dogs), because this would expend too much energy.

Instead, weasels roam their landscape and—upon seeing potential prey—attack it without hesitation, depending on their speed and agility to end the chase quickly. (And nearly anything they encounter can be a target; weasels will take on rabbits ten times their weight.) They then quickly immobilize their prey by severing its spinal cord with a single bite to the back of the head.

Weasels have evolved other distinctive—and controversial—habits to cope with their constant need to eat. Unlike many carnivores, which demand fresh meat, they often kill far more than they can eat in one sitting, caching the rest in “larders” (often found in burrows or rockpiles). The ability to store food today means that they might not starve tomorrow.

Unfortunately weasels can’t always tell wild prey from domestic. This has made them notorious among farmers for raiding henhouses and killing all the hens inside.

This reputation is at least partly unfair, as studies have shown that rats turn out to be the real culprit in many cases. In addition, weasels tend to keep farmyards and buildings clear of rodents, which carry disease and are extremely destructive to crops.

And even when weasels are responsible for killing chickens, it’s important to remember that they’re filling their larders, not engaging in purposeless slaughter. (Not that this distinction is any consolation to the farmer.)

Regardless, weasels’ hunting habits—along with their admittedly unsettling speed, snakelike movements, and ability to get into seemingly predator-proof places—have made their common name into a common insult. “Weasel” has come to refer to sly, sneaky, untrustworthy people, ones who will betray you with “weasel words” as they take advantage of you. You should never trust weasels…or even take your eyes off them.

While we weren’t concerned about betrayal that day in Rockefeller State Park, we did find it hard to take our eyes off the one and only Short-tailed Weasel we’ve ever seen there. But that was because we were watching a tiny, glorious predator, perfectly adapted to survival in the environment we were fortunate enough to share. And, even more impressively, it was a member of a fierce, independent family that has somehow managed to survive—and even thrive—in our crowded, human-dominated world.

Copyright © 2021

By Joseph Wallace

A few weeks ago, while scanning for ducks, unusual gulls, and other birds the Verplanck waterfront, a group of birders spotted a large, hump-snouted, definitely non-birdlike head sticking up from the Hudson River’s surface. It was a male Gray Seal, a rare species—even a rare class (Mammalia)—to glimpse in in these waters.

Rare…but not unprecedented. Late fall to early spring is seal season in the Hudson and its tributaries, and over the past few months waterfront observers and lucky kayakers have also spotted the more commonly seen Harbor Seals (a smaller, sleeker relative of the Gray) off Croton, Saugerties, and other locations. In recent years, other seal species, including Hooded and Harp, have also made appearances in the river.

The most remarkable of these sightings involve a Harbor Seal first spotted in the river and nearby Esopus Creek in Saugerties on August 21, 2019. The animal then spent 533 (seemingly contented and healthy) days in the area. It was last reported on January 14, so it may finally have departed, perhaps due to extensive ice floes in the Hudson or the muddy quality of Esopus Creek in this season. 

A white tag placed on the seal’s flipper when it was a pup—and reported many times during the animal’s subsequent wanderings—allowed scientists to track its journey. Rescued as an abandoned pup from an island in Maine, the seal was rehabbed by the Mystic Aquarium Animal Rescue Program, tagged, and released off Rhode Island in the spring of 2019.

The young animal then traveled 80 miles up the Connecticut River before encountering an impassible dam, where it reversed course and headed back to the ocean. It eventually ended up in New York Harbor and then the Hudson River estuary. Traveling upriver, it reached Saugerties, where it decided to stick around for a while.

It’s impossible to know for sure if there are more seals in the Hudson now than in years past, but it seems likely. The river is cleaner and fishing regulations are stricter than they have been in decades, making the river a much more welcoming environment for these fish-eaters.

But it’s more than that: The seals that visit the Hudson are also part of a much wider phenomenon taking place all along the coasts of the northeastern U.S. and eastern Canada. Throughout the region, populations of both Gray and Harbor seals are booming, with some breeding colonies growing at an annual rate of twenty percent or more a year.

It’s important to realize that this encouraging trend merely represents seal populations reclaiming what had previously been lost. In historical times Gray Seals were abundant across the North Atlantic, while Harbor Seals—the world’s most widely distributed seal—thrived in northern oceans around North America, Europe, and Asia.

Unfortunately, what happened to these two species during the 19^th and first half of the 20^th century is a familiar story of human exploitation. In the United States and Canada, they became the targets of intensive hunting for meat, oil, and their skins. They were also culled, supposedly to protect local fishing stocks. (In Massachusetts as late as the 1960s, each seal nose turned in earned its hunter a $5 bounty.)

The consequences of this decades-long persecution were predictable: Seal populations plummeted. By 1970, the region’s entire population of Gray Seals, for example, may have dwindled from as many as 150,000 to as few as 5000 individuals, almost all off Canada. Both species were virtually extinct along the U.S. coast. 

In the 1970s, however, a series of laws in the U.S. and Canada granted both seals significant protection, and almost immediately their numbers started to rebound. The increase has been ongoing since then, and today scientists estimate that there are 140,000-150,000 Gray and 70,000-100,000 Harbor Seals off the northeast coast.

Even apart from Hudson River sightings, it’s easy to notice the increase. When I was a kid on Cape Cod, no one ever saw—or expected to see—a seal. These days, however, a quick scan from an ocean beach on the Outer Cape will usually reveal at least one Gray Seal rolling and diving just offshore.

And sometimes far more than that. In winter, my family and I have watched thirty or more Gray Seals congregate close to the beach, seemingly as interested in us as we are in them. (A reliable way of attracting a seal horde: Jump around or dance on the sand, something my own kids enjoyed doing when they were little.)

Along with the animals’ entertainment value and the fulfilling knowledge that we can still coexist with other large mammals, booming seal populations have had more complicated consequences. It all starts with the simple fact that there are a lot more humans around here now than there were the last time seals were so abundant, and thus a far greater demand for the fish that both seals and humans depend on.

With commercial fisheries and the sport-fishing industry both already under pressure, the increasing number of seals has provoked an outcry all up and down the coast. (Gray Seals especially have been known to take big Striped Bass and Bluefish right off lines within full view of the person who’s reeling in a catch…not a behavior designed to win friends.) Despite some scientists’ belief that seals have only a negligible effect on fish stocks, calls for renewed hunts or culls are rising.

Making the issue even knottier is a recent phenomenon that has drawn attention worldwide. Great White Sharks, which feed on seals, have followed Gray Seals close to the shores of Cape Cod, often to within a stone’s throw of the most popular beaches. More than 150 Great Whites were recorded around the Outer Cape in 2019 alone.

Several times in recent years, beachgoers have watched—and filmed—a Great White Shark as it killed a seal in the exact spot where they’d swimming just minutes before. And though attacks on humans are very rare, they aren’t unknown: In September of 2018 a surfer was killed by a shark off a popular Wellfleet beach.

Much of Cape Cod’s economy relies on tourist dollars. While some businesses have embraced the Cape’s new “come see the real-life Jaws!” reputation, most worry about the ultimate fate of a beach resort area where people don’t feel safe going in the water. Alongside calls to kill sharks, the chorus to reduce the population of seals has grown even louder.

So what’s to be done? For now, both seal species remain fully protected and the sharks unmolested. And Cape Cod’s residents and visitors are trying to stay safe through education, signage, aerial surveillance of offshore waters, satellite tagging of sharks, and other methods. (For example, high-tech buoys near some beaches ping a warning when a tagged shark is nearby.)

But the longer-term story remains to be written. Right now, both Harbor and Gray Seals stand as emblems of how, through strong regulation and careful management, we can help wild creatures survive in our increasingly crowded and complicated world. Yet they also illustrate one of myriad challenges we must face in the years to come: Once we’ve allowed a species’ population to recover, what happens to it—and to us—next? 

by Joseph Wallace
Copyright © 2021

It had already been a long night. I’d worked late, and after finally making it to bed had tossed and turned before finally slipping into an uneasy sleep.

I’d given myself permission to sleep late the next morning, but it turned out the choice wasn’t mine to make. At first light, a joyous song—“Teakettle Teakettle, Teakettle, Tea!”—rang in the new December day from just outside the bedroom window. A moment later, it was joined by a second. And then a third.

I lay there for several minutes, listening to the three vocalists vying to show who could greet the day most enthusiastically, before bowing to the inevitable and hauling myself out of bed. I knew who these songsters were (as, I’m sure, do many of you): Carolina Wrens, the definition of persistently noisy neighbors. There would be no more sleep for me that morning.

Today, the boldly patterned, endlessly active, and bright-eyed Carolina Wren is one of the Northeast’s most familiar year-round species. But it wasn’t always this way. The first time I saw one, I was a teenager on Cape Cod, birding with my dad. When we spotted a buffy little bird perching on a nearby branch and letting loose with a ringing song, we had to pull out our trusty Peterson’s field guide to tell us what it was.

This was in the 1970s. The Carolina Wren was already breeding in parts of the Northeast back then, but its true home was largely the Southern states. (It’s the state bird of South Carolina.) In the decades since, though, the wren has steadily expanded its breeding range northward, today nesting as far north as Ontario and Quebec. It has also begun to overwinter in some of its northern range; hence the clamor that awoke me to a December dawn.

As with other “southern” species (e.g., Black Vulture) that now spend the winters here, the wren’s expansion is partly due to our warming climate. Other human-wrought changes to the environment, however, have also helped.

For example, the birds’ preferred habitat includes vine tangles, woodpiles, and secondary forest with dense underbrush below, all of which are in abundant supply in northern suburbs and parks. And, like many other birds that eat mostly insects and spiders during warm weather, the wrens switch to a mainly seed-based diet in the winters, and therefore can rely on backyard birdfeeders. (Where, I can report from personal observation, they shovel large quantities of seed to the ground while seemingly searching for the most delicious ones.)

Yet the story of the Carolina Wren’s recent success in our area goes deeper than the warming climate, habitat, and food supplies. Many of its most distinctive (and entertaining) advantages are specific to the wren alone.

For instance, most birds sing almost exclusively during nesting season, but—as we well know—not Carolina Wrens. Vocal all year round, and territorial, too, they are on the lookout for a mate at any time of year. And once they’ve paired up, they usually stay together for life.

This means no muss, no fuss, no wasting precious warm-weather days seeking a partner. Come the first hint of spring and they’re ready to get to work on the nest.

Nor are they picky about where they choose to raise their young. Although all Carolina Wrens nest in cavities, their definition of that word is exceedingly generous. Along with the traditional holes in trees, they’ve been known to choose boots, mailboxes, working light fixtures, the pockets of jackets hanging on nails, and a host of other “cavities”…and to raise their young successfully in every one.

The rewards of an early start and flexibility in nesting sites are dramatic. While most species raise only a single brood each year, Carolina Wrens can successfully rear as many as three—with as many as seven eggs each time—in a single breeding season.

In the north, severe and snowy winters will often cause wren populations to crash. But the birds’ ability to produce so many young means that these populations usually bounce back quickly. In fact, the number of Carolina Wrens in the Northeast has been increasing steadily during the past few decades. (Recent Christmas Bird Counts throughout our region turned up record totals of the species.)

While I confess that didn’t feel much affection for them as I lay awake that cold winter morning, Carolina Wrens have become among my favorite birds. By singing anytime, eating anything, and nesting anywhere, they seem like true survivors, ever ready to take on whatever challenges the dangerous world throws at them. That’s a bird I’m happy to sing the praises of—day, night, or crack of dawn.

By Joseph Wallace
Copyright © 2021

A skim of new ice in a calm inlet. A scattering of Bufflehead ducks, each shining like a black-and-white beacon amid the river’s silvery swells. Six Bald Eagles—no, eight—soaring and tumbling in the sky above the whitecaps.

These are among the highlights of a morning walk in Croton Point Park at this season. What they—and so much else, seen and unseen—all share is the presence of the Hudson River, which dominates not only the landscape but much of the cycle of life in our region.

What makes our area’s stretch of river such a haven? A variety of factors, chief among them water temperature. As near as Albany, the Hudson’s temperature has fallen to about 37 degrees. But the waters in and around Haverstraw Bay currently remain in the high 40s, a vitally important difference to many species seeking food and shelter during the coldest months.

Buffleheads, a common winter visitor in the bay and surrounding waters, are among my favorite birds. Their name—supposedly drawn from the fact that their heads, bulky for their size, resemble those of bison—is fun to say out loud. Their eye-catching pattern makes for a striking contrast against the silvery winter river. (In good light, the “black” on their heads and neck shines with beautiful purple-green iridescence). And the way they play peekaboo, disappearing instantly beneath the surface in dives that can last for many seconds, seems like a magic trick.

But perhaps the most appealing thing about Buffleheads is how intrepid they are. These tiny ducks are only about half the length of the Mallard and weigh little more than a pound, yet they are undeterred by the frigid air and icy waters where they make their winter homes.

They do grant one concession to the weather: They’re rarely seen on the open ocean, instead congregating in protected bays and rivers and near the coast. Here they find the snails and crustaceans that make up most of their winter diet.

We may never witness this around here, but it’s always fascinating to learn what “our” visiting birds are doing in other seasons. Buffleheads, for example, have evolved a fascinating breeding strategy on their nesting grounds to our north.

Unlike most ducks, they do not nest on the ground. Instead, they choose preexisting tree cavities, relying almost exclusively on holes originally excavated by Northern Flickers. Thus Bufflehead populations are dependent on birds they otherwise have little connection with…and on forestry practices that leave dead and dying trees standing.

While Bald Eagles are glamorous and easily identifiable, they are far from the only raptor you can see in this region during winter. (Red-tailed Hawks and the smaller Sharp-shinned and Coopers Hawks are fairly common, while several other species make rarer appearances.) But eagles stand out: They are so huge—and their population growth since the 1970s so spectacular—that even non-birders take notice.

Fifty years ago, eagles had virtually vanished from the Northeast. Among the culprits were habitat destruction and pollution of the lakes and rivers the birds depended on for food. Most notoriously, though, pesticides (chiefly DDT) caused female eagles to lay eggs with thin, fragile shells, causing nesting failures that persisted for year after year.

Only when the birds were nearly gone did aggressive recovery efforts get underway. The banning of DDT, coupled with an aggressive reintroduction program using birds from healthier populations to the north and west, eventually reversed the decline and led to a new eagle population boom. Today, more than 100 pairs nest in the Hudson Valley, and even more visit in the winter.

In all seasons, the river is what attracts Bald Eagles to this region. As the winter comes on, and rivers and lakes further north start to ice over, the open waters of Haverstraw Bay (where the Hudson is at its widest) and to its south serve as a magnet for the region’s eagles.

During especially cold snaps, ice floes float up and down the Hudson with the tides. At these times, you can look out over the river—especially between Peekskill and the Tappan Zee Bridge—and see dozens of eagles either riding the floes or riding the air currents above them.

Not every creature that takes advantage of the river is as attention-grabbing as the Bald Eagle. During the warmer months, for example, the turbid waters and abundant vegetation of Haverstraw Bay provide a haven for young Striped Bass, among many other fish species. In the winter, though, while these young fish move south to New York Harbor, adult stripers congregate in the bay, where they find the water temperatures and salinity levels they prefer.

A less spectacular fish found in the bay at this season is the Atlantic tomcod. This is a species that thrives in cold water (its nicknames include “frostfish” and “winter cod”) and lives as far north as the Gulf of St. Lawrence and northern Newfoundland. Their mid- to late-winter spawning runs often take place under ice-covered waters.

Perhaps the most unexpected fact about tomcod involves the species’ response to General Electric’s dumping of PCBs into the river between the 1940s and 1970s. While this ongoing release of toxic chemicals had a disastrous and long-lasting effect on other species, the tomcod survived…and even thrived.

The cause of this unusual success: Rapid-fire evolution in action. A small number of tomcod had a rare genetic mutation that provided resistance to PCBs.  Via natural selection, the mutation quickly spread throughout the river’s tomcod population. In recent years, scientists have found that the mutation now occurs in 99% of all Hudson River tomcod, compared to only 10% of those found in other waters.

Unfortunately, not all threats to the tomcod have been overcome by evolution. This species relies on cold waters, and with the warming of the river due to climate change, the tomcod’s Hudson River spawning runs have diminished significantly in recent years.

Climate change is just one of the continuing threats to the health of the river and its inhabitants. Deforestation, pesticide and fertilizer runoff, and other effects of the nearby—and ever-growing—human population also pose ongoing challenges.

Other threats to the river’s denizens remain more mysterious. As local vultures—and anyone walking along the river in recent weeks—can tell you, a large die-off of Atlantic menhaden (also commonly called bunker) has been taking place in Northeastern waters—not only in the Hudson River, but all the way from Cape Cod to South Carolina.

New York’s Department of Environmental Conservation (DEC) is studying potential causes, but as of this writing has not released its conclusions. Scientists in Connecticut, however, have pointed to a recent bunker population boom as a factor. A boom, in fact, that is a direct reflection of the increased health of our inshore waters, thanks to more stringent regulation of commercial fishing limits and pollutants.

One result of these regulations: So many millions of bunker massing in our waters this fall that some were caught by dropping temperatures and dwindling food supplies before migrating south to warmer climes. The die-off, researchers point out, may seem dramatic to those onshore, but actually encompasses a minuscule fraction of an increasingly healthy fish population. New York’s DEC will soon confirm whether the Hudson River die-off can be attributed to the same causes.

Whatever the reasons prove to be, however, the menhaden die-off serves as a reminder that the river may dominate our landscape, but we still dominate the river. And that our responsibility to protect and manage it, and the creatures that rely on it, is a challenge for all seasons. 

By Joseph Wallace
Copyright © 2020

In George R. R. Martin’s Game of Thrones, the people of The Kingdom of the North build a 700-foot-tall wall between them and the wild lands to their north. Their crucial goal: To keep out the White Walkers, mysterious creatures with a propensity to invade and wreak havoc. When the wall is finally breached and the Kingdom invaded, the residents’ response is all-out war.

Every few years, our northern latitudes are also swarmed by beings that more typically reside to our north. Our response, though, is quite different: We welcome the invaders happily. We even feed them.

Of course, our visitors aren’t icy creatures bent on our destruction. They’re birds, mostly finches, that are known as “irruptive species.” This means that they have the habit of sporadically and unpredictably heading south (“irrupting”) in vast waves from their homelands in the northern boreal forests and the Arctic.

Luckily for those of us who have set up feeders, or who merely keep an eye out for birds, this fall and winter are shaping up to be one of the most spectacular irruption years in recent times. Several northern finch species have already started making regular appearances at local feeders (and throughout the Northeast and, often, across much of the Lower Forty-eight). Others seem to be on their way as well.

Here’s a quick guide to what you might be seeing now or have the chance to see during the months to come, when birds give us glimpses of the natural world to lighten the dark days of winter.

PINE SISKINS

Most years, you won’t see a single one of these cousins to the familiar American Goldfinch. But when this heavily streaked smaller finch does choose to invade, it really invades. One day a few weeks ago we had at least thirty Siskins in and around our feeders at one time. (In the face of numbers like that, even House Sparrows give way!)

Pine Siskins don’t usually stray far from the boreal forests that are their home. This year, though, because of a comparative meager cone crop in the conifers they usually rely on for winter food they’ve headed south—not just to New York, but in big invasion years like this one, even as far as Mexico and Guatemala!

One interesting note: Unlike most small songbirds, which migrate at night, Siskins were always thought to be diurnal migrants. At the height of invasion waves this fall, though, they’d been seen flying by night as well. Perhaps there are simply too many of them to fit into the daytime flight paths!

PURPLE FINCH

A moderately close look is all it takes to tell a Pine Siskin from a Goldfinch, but identifying this visitor can be a trickier proposition. At a glance, Purple Finches look a lot like the House Finches that are among our most frequent feeder visitors. But Purple Finches are generally heftier, with fewer streaks, a richer purple color on the head and extending further down the breast (though both species’ colors can be variable), and a larger, straighter beak.

Females Purples can be easier to tell apart from their House counterparts. Along with heavier, darker streaking, they often have a bright white “eyebrow,” which makes for a clear ID.

Purple Finches have been regular at local feeders for several weeks now. Like the Siskins, they’re in search of food, but the causes are different. During nesting season, Purple Finches favor the Spruce Budworm, a moth whose caterpillar can defoliate and even kill large swathes of spruce and fir forests. In years of extensive outbreaks, like this one, the finches enjoy great breeding success.

Come fall and winter, with no Budworms available, the bumper crop of birds has to travel south to find food. Our feeders provide them with a welcome opportunity.

EVENING GROSBEAK

For us, a backyard visit by three of these relatives of the familiar Rose-breasted Grosbeak was one of the delights of the fall. They were the first my wife and I had seen south of Vermont, and even there these colorful birds are not a common sight.

Evening Grosbeaks are easily told from other feeder visitors by their size, their yellow-dominated or -tinged coloration (in a season when even goldfinches are drab) and their huge, yellow-ivory bills. They’ve moved south for the same reason as the Purple Finch: Spruce Budworm outbreaks led to an increased—and now hungry—population.

REDPOLLS and CROSSBILLS

There are two Redpoll and two Crossbill species, all of which are only rare winter visitors to our area. But in this remarkable invasion year, Common Redpolls have already been spotted in Croton Point Park, and both Red and White-winged Crossbill species not that far north of Westchester. 

For many years, I thought that spring migration was the best time to pay full attention to birds. Chasing after the species returning to nest or simply passing through, getting to glimpse their variety and vivid colors after a long, bleak winter, was intoxicating.

I still love spring migration, still love the chase. But over the years I’ve learned that all times of year can be intoxicating for birders. Especially now—what I used to consider the “off-season”—when any day can bring a new, unexpected, and welcome invader from the north.

Copyright © 2020 by Joseph Wallace

Recently my wife and I took an early morning walk in Croton Point Park. Again and again we were reminded that, while most of us humans remain stuck near home, for countless birds this is peak season for arrivals and departures.

Some of the species that were familiar sights in the park all spring and summer—such as the Purple Martins that raised their young in the condos near the front entrance—are have long since headed off to warmer climes. Others that we think of as year-round residents—like Black-capped Chickadees and Common Grackles—are still here, but with an unexpected wrinkle: Most are not the same individuals we saw all summer, having arrived from further north while “ours” have flown south.

Meanwhile, the group of birds known as passage migrants—species that neither breed nor winter here, including most warblers, vireos, and shorebirds—continue to stop off to rest and feed before resuming their own journeys south. And a handful of fascinating species that merely winter in our region (like the Lapland Longspur, which nests in the High Arctic) have also started to arrive.

Because so many migrating birds are small and garbed in drab fall plumage, they can be easy to miss. But any observant visitor to Croton Point is nearly guaranteed to spot perhaps our most spectacular recent arrivals: birds of prey, which seem to be overflowing the park these days.

On our recent walk, we were lucky enough to get good looks at two closely related hawks from the group known as accipiters: the tiny Sharp-shinned and larger Cooper’s Hawks. Be careful with the ID, though: A large female Sharp-shin isn’t much different in size from a small male Cooper’s, and they also share comparatively short, broad wings and long, banded tails.

As is true for most Northeastern raptors, populations of these handsome hawks crashed by the 1970s due to DDT use, but they have since recovered spectacularly. Both species thrive in suburban woodlots, where they hunt smaller birds. (They can even take up long-term residence near bird feeders, putting pressure on local songbird populations.)

On our walk, we watched a Cooper’s Hawk chase—and be chased by—another regular denizen of the park these days: a Northern Harrier. This distinctive raptor (look for the long wings held in a “V” shape, prominent white patch on its rump, and roundish, owl-like face) makes for a memorable sight as it quarters low over the hill.

The Harrier is considered threatened In New York State. As so often, the main threat to the species is habitat loss, in this case the filling of marshes and conversion of unmowed grasslands to other uses.

Other frequently seen species in the park are clearly not threatened in our area…but they were not that long ago. Famously, for example, both Ospreys and Bald Eagles also saw their populations crash due to DDT, to the extent that by the 1970s some scientists thought they might go extinct in the Northeast.

Of course, that’s not what happened. The banning of DDT, careful protection, the cleaning up of the Hudson River, the building of nest platforms for Ospreys and, especially, New York’s Bald Eagle reintroduction program all bringing both species back in spectacular fashion. Even a short visit in the fall will usually feature at least one Osprey, often carrying a fish as it stokes up for its southward journey. And late fall through winter is prime season for eagle-spotting, as birds from further north move down this way in search of open water.

Surprisingly, the most spectacular sightings during our walk didn’t involve huge, showy birds like the eagle or Osprey, but one of the region’s smallest raptors: the American Kestrel. In little more than an hour, we saw more than a dozen of these slender, fierce little falcons, many of which are stopping off en route to the southern U.S. or Central America.

At one point at least half a dozen Kestrels rose into the air at once to dive-bomb a passing Cooper’s Hawk. To see so many birds of prey in a single moment was stunning and heartening.

American Kestrels remain one of the most common raptors in the United States, with a population estimated at 4 million individuals. However, this is also a species in rapid decline, populations having decreased by at least 50% nationwide in recent decades.

One challenge for any efforts to slow the Kestrel’s decline: No one can be sure exactly what’s causing it. Most likely, it’s a combination of factors: habitat loss that results in fewer places to hunt; overuse of neonicotinoids and other pesticides; plummeting populations of grasshoppers and other large insects, which are among the Kestrel’s main food sources; and competition from European Starlings, House Sparrows, and other species for a dwindling number of nesting cavities.

The view of so many different raptor species, ranging from tiny to huge, during a single walk feels like an unexpected gift. But it’s one that also demands we think more deeply about the inextricable ways our birds’ fates depend on the choices we humans make, both now and in the future. And, just as crucially, how vital it is that places like Croton Point Park remain refuges for raptors—among so many other birds—during this time of comings and goings, and always.

“Nature abhors a vacuum,” is how the famous phrase goes. Whenever I see it, though, I always think it’s missing a follow-up sentence: “And evolution is the process that allows nature fill that vacuum.”

As I research topics for this blog, I always marvel at how every imaginable ecological niche is filled with living things beautifully suited to its demands and rewards. Animals and plants that have evolved in size, shape, and behavior specifically to be able to survive, to thrive, there.

With all their diversity, birds provide endlessly vivid examples of this phenomenon. Just in our area, a few moments’ looking around might reveal a Ruby-throated Hummingbird hovering as it drinks nectar (wing beats per second: 50); a Turkey Vulture soaring effortlessly on thermals as it searches for carrion (wing beats per second: 0); an American Robin yanking up worms (that it’s heard wriggling beneath the earth) from a manicured lawn; and a Barn Swallow darting and twisting with stunning agility as it gobbles up tiny flying insects.

Four members of the same group of living things, each species so different and so perfectly adapted to the niche it fills. And since they are all so commonly seen, so familiar, it’s easy to forget how distinctive their adaptations are.

To me, though, among the most extraordinary niche-filling feat in birds is less visible: The life cycle of shorebirds, the sandpipers and plovers that move through our region each spring and fall.

Or maybe that should read spring and “fall.” Because not only is southward shorebird migration happening right now, it’s already been going on for several weeks. Along with reminding us of how imprecise our definitions of nature’s timelines can be, these little birds also tell a vivid story of adaptation and survival.

Not all shorebird species we see are passage migrants. The Killdeer (a plover), for example, nests in this area at such locations as Croton Landing and Croton Point Park. Some individuals actually spend the entire year here without migrating at all.

But the vast majority of sandpipers and plovers we’re spotting these days on local riverbanks, beaches, and mudflats are merely stopping to rest and refuel before heading on. They’re following an unusual—and unusually challenging—schedule, one demanded by the characteristics of the ecological niche they have evolved to fill.

The story of one shorebird species, the Semipalmated Sandpiper, is both dramatic and characteristic. These tiny birds—6 or so inches long and weighing less than two ounces—nest on the Arctic tundra of North America. They spend the winters, however, in South America, sometimes as far south as Tierra del Fuego. (Roughly a 9,000-mile trip each way!)

As if that isn’t demanding enough, some Semipalmateds take off from the New England coast and don’t land again till they reach South America. This nonstop hop, completed without food or rest, can cover 2,500 miles.

The challenges don’t end there. Naturally, summers on the tundra are extremely brief, as is the Semipalmated Sandpipers’ access to the food sources (insects, crustaceans, marine worms) they depend on to survive and raise their young.

Therefore, while the birds don’t arrive till May, nesting season has to be finished by early July. (If their first nest fails, they do not try again.) Unlike more temperate species, neither adults nor the newly fledged young can take weeks to build their energy before heading south. They have to start their journey almost at once.

That’s why, by early August—when some less itinerant local nesters are still raising their second broods of the season—Semipalmateds start to show up here and in migration stopovers across the U.S. (Those whose nests failed up north may start appearing even earlier.)

And they’re far from the only species on a tight schedule. The Least Sandpiper—the smallest shorebird in the world, less than 6 inches in length and weighing in at a single ounce—is another marathon flyer, nesting on the tundra and wintering as far south as Chile. And, while both Greater and Lesser Yellowlegs don’t have as far to travel—they nest in boreal forests and wetlands and some winter over within the U.S.—they have also started to pass through our region.

It’s always a little bit of a shock to see the first shorebirds showing up in midsummer, when the last thing I want to think about is the changing seasons. But it also reminds me that migration (and the avian evolution that underlies it) is a fascinating—and remarkably complex—spectacle, filled with surprises and moments of enlightenment. And that we get to witness it, in all its complexity, every spring and fall.

By which, of course, I really mean “fall.”

Copyright © 2020 by Joseph Wallace

Ever since the first flowering plants emerged about 130–140 million years ago, they and those that eat them have been engaged in a kind of evolutionary arms race. As plant-eaters chase them down, plants, which obviously can’t run away, have developed other ways to defend themselves and the flowers and seeds that sustain their species.  

Plants play defense via such obvious physical attributes as tough leaves, thorns and spines, and the sheer abundance of the seeds they produce. (One vivid local example of this last survival strategy is the cottonwood, which blankets some neighborhoods in “snow” every spring.)

Another widespread adaptation is also effective: Many plants have a bitter taste, and some are poisonous. They’ve developed an astonishing array of chemical compounds that serve to teach anyone who dares to eat them not to do so again. Scientists have identified more than 3000 separate alkaloids (one group of such compounds), and a single plant can produce 30 or more.

Humans being human, we’ve learned to use some plant toxins for our own purposes: For remedies (e.g., digitalis derived from foxglove plants and used to treat heart problems), in “recreational” drugs (the psychoactive ingredients in cocaine), and as seasonings for our foods. (Capsaicin in chili peppers is meant to deter you from eating them.)

Other animals have also learned to put these toxic chemicals to use. In one remarkable example, small tropical insects (most likely ants), far from being harmed, store plant alkaloids in their own bodies to use as a defense system. But it doesn’t always work: Certain frogs still gobble the ants down, having evolved special glands to sequester the same toxins in their skin. These are the Dendobatid frogs, commonly known as poison or poison-dart frogs, and some of them are so toxic that merely holding one can cause serious neurological, respiratory, and other effects in humans.  

The never-ending battle between plant and plant-eater has also led to the development of microhabitats. These are tiny ecosystems populated by insect species that share one central trait: the ability to eat a plant that most species find toxic. We can find one vivid example of this phenomenon in our own gardens and fields right now.

Not many years ago, milkweeds were considered merely denizens of vacant lots and untended roadsides, no more or less remarkable than a hundred other weeds. What changed their status, of course, was the besieged Monarch butterfly, whose caterpillars eat milkweed…and only milkweed.

Milkweed sap contains chemicals known as cardiac glycosides, which are toxic to most insects and animals and can cause serious symptoms in humans if consumed in large quantities. The sap is also thick, sticky, milky, and hard to clean off your hands, and it can burn if it gets in your eyes. Very few species will dine on a milkweed plant more than once. 

The Monarch caterpillar and some other species, however, find it delicious. These species benefit from their specialized tastes for a simple reason: When most plant-eaters find your chosen food toxic, you don’t encounter much competition for resources.

Yet the benefits of an all-milkweed diet run far deeper. Like the rainforest ants and poison frogs, Monarch caterpillars and butterflies store the plant toxins in their own cells, which makes them as poisonous as the plants they depend on. In a further evolutionary development (also shared with many poison frogs), they’re boldly colored. Predators of all kinds seem to recognize their yellow- or orange-and-black markings as caution flags: Avoid!

Another common milkweed resident, The Milkweed Tussock (or Tiger) Moth, whose caterpillar has bright orange-and-black tufts and adult a tiger-striped abdomen, shares both the Monarch’s toxicity and warning colors. Fascinatingly, though this color palette warns predators away from the caterpillars, it’s useless against the bats that prey on the night-flying adult Tussock moths. So the moths have evolved a secondary defense: They have special organs that emit clicking sounds, alerting the bats to the moths’ bitter taste.

Similarly, both Large and Small Milkweed Bugs boast bold orange- or red-and-black patterns. So does the Red Milkweed Beetle, a member of the longhorn beetle family. (Remarkably, in this species the base of the long antennae actually bisects the insect’s eye, which gives it its genus name: Tetraopes, meaning “four-eyes.”)

Not every insect that takes advantage of the milkweed microhabitat needs such evolutionary adaptations, however. Some just like to spend time there.

Unlike the sap, milkweed nectar contains no cardiac glycosides, and the abundant, long-lasting flowers are popular with a wide variety of butterflies, moths, bees, and other pollinators. Inevitably, the presence of such insects also brings creatures that prey on them.

The Golden (or Goldenrod) Crab Spider, for example, can frequently be found amid milkweed flowers. There it sits quite still, waiting to ambush an unwary bee, butterfly, or other visitor.

As with so many inhabitants of this microhabitat, the spider’s life story contains some unexpected details: It is one of only two spider species in North America that can change color to match its background. It can be white with green or purple patches (good milkweed camouflage), or bright yellow (preferred in another favorite habitat, goldenrods.)

Researching this essay, I was amazed by how much I hadn’t known about the milkweed’s world. But the truth is that microhabitats exist everywhere—in leaf litter, the soil beneath your feet, the trees on your street—and they’re all just as intriguing. I’m looking forward to exploring more of them soon…and telling their stories here.

Joseph Wallace