Whither the Migration of Monarch Butterflies?

Though the number of butterflies in general was radically down this summer, I still saw the occasional monarch. Some appeared frantic. Were they searching in vain for a mate? Other times they'd pause on a flower to take a long drink of nectar. Sometimes I'd just see a flash of orange out of the corner of my eye. No other butterfly can match a monarch's nimble power in flight. The number of sightings, maybe ten in all, wasn't much changed from previous years.

Their longterm prospects, though, are very much in question. Chip Taylor, who has tracked migrations as closely and for as long as anyone, says that monarchs as a species will survive, but their fabulous migration will not. Last year's overwintering numbers on Oyamel fir trees in the mountains of Mexico was the second lowest ever recorded. Resilient as the monarchs are, it's hard to imagine the delicate dynamic of migration surviving the rapidly increasing disruptions of climate change.

Yes, climate has changed in the past. It's said that, before humans started altering the atmosphere, the earth experienced a progression of ice ages every 100,000 years or so. During the last ice age, glaciers extended south almost to what is now NY City. What we have now is change at a speed far beyond the capacity of species to adapt, as our machines pour a massive overdose of carbon dioxide into the atmosphere.

In a blog entry this past August, Taylor explained how extremes of weather can affect the monarchs' capacity to build numbers over the summer and migrate back to Mexico in the fall. Extended heavy rains in early summer can delay egg laying. Warmer temperatures in September and drought in October can impede a fall migration historically aided by cool winds out of the north. What we got this year was hot and dry, with three months of drought and warm weather extending into mid-November. That's a radical departure from anything I've ever witnessed.

Each year towards the end of October, I start looking for news about the migration south to Mexico. The first headline I found confirmed my suspicions: "This fall's monarch butterfly migration through Texas doesn't look promising." Then, finally, a report on-site at the roosting grounds in Mexico. Though a few had been straggling in over the past few weeks, the first largish group of 2000 monarchs wasn't reported until Nov. 21. In past years, monarchs would predictably arrive en masse in the first week of November. Then, after the monarchs had settled into their roosts, the Biosphere Reserve would be opened to tourists mid-month. This year that opening was cancelled, stranding those tourists who had traveled far to witness a unique example of nature's splendor. This is not the only destination being compromised in a world being heated in part by global tourism. There are different ways to show love for nature. Touristic love, which I was a part of in the past, becomes more ironic by the minute.

The radically dry, warm weather we've experience this fall has a lot to do with the increasing instability of the jet stream--high winds out of the west that normally feed us a steady stream of contrasting weather, but can get blocked and diverted north or south, causing weather systems to linger indefinitely. The jet stream is driven by the difference in temperature between the tropics and the arctic. As the arctic heats more quickly than lower latitudes, the temperature gradient is reduced and the jet stream becomes more malleable. 

Consider the extraordinary ambition and brilliance of the monarch butterfly's eastern migration. Huddled overwinter in the mountains of Mexico, its numbers head north in March, then each succeeding generation--usually four total--fans out from Texas to harvest the richness of flowers and milkweed foliage from the whole eastern half of the U.S. and even up into Canada, before somehow knowing how to navigate all of that embodied richness back to their little hideout in Mexico. Over the past million years, the distance flown would have contracted during ice ages, then expanded as the glaciers withdrew. I think of the monarch migration as akin to a rubber band, stretched northward by the supply of nectar and milkweed, then contracting back down to Mexico for the winter.

The vast territorial expansion each summer is surely dependent on numbers. Otherwise, how will the monarchs find each other to mate as they spread out across the continent? Though much different in behavior, the passenger pigeon was also dependent on big numbers. Its demise, more than a century ago, was due to radical habitat change and a wanton harvest and slaughter that Aldo Leopold described as "trigger-itch." Now, our itch is to take photos, and our intention is to preserve. And yet, we watch as the collateral damage of a machine-driven economy accumulates.

A post on the Monarch Watch Blog describes the Symbolic Monarch Migration that school kids in Mexico, the U.S., and Canada take part in. Kids in Mexico send paper monarchs to kids up north in the spring, and vice versa in the fall. Monarchs ignore country boundaries. They are telling anyone who takes time to listen that our interests don't stop at the border, what we do affects people and nature far away. 

One halcyon autumn day when I was a kid, walking across the broad lawns surrounding Yerkes Observatory in Wisconsin, I was astonished by the sight of countless thousands of monarchs flying above me. There was a thrilling collective energy to their flight, not dutifully unidirectional towards the south but instead more like a dance. They seemed to feed off of each other's proximity and energy--an uncanny mix of whimsy, skill, and determination. 

If the great migration were to be lost, monarchs would still persist in pockets further south, but they wouldn't be the same monarchs we've known and loved. Here's a post on how the loss of migration's rigors would change them.

How Are Monarchs Doing in 2024?

Several times a year, the question of "How are the monarchs doing?" rises in my mind. An internet search typically ends up at Chip Taylor's blog on Monarch Watch. There you will find thoughtful commentary and deep analyses, a mixture of good news and bad news, as this extraordinarily resilient species faces ever greater challenges. In 2024, overwintering numbers in Mexico were the second lowest ever recorded, with 2013 having been the lowest. Chip's more recent posts tell of a rebound this summer, as this robust and prolific species has increased its numbers during its migration, following the growth of milkweed north in a tagteam of successional generations, spreading into all corners of the eastern U.S.. 

I've had maybe five sightings of monarch butterflies this summer--a typical number. One appeared frantic, as if it had been searching the great outdoors in vain for a partner. Another was laying eggs on a patch of common milkweed at Mercer Meadows--a beautiful and hopeful sight. Another, pictured, was in my front yard on busy Harrison Street in Princeton, gathering nectar on a swamp milkweed. 

A few days ago, one was nectaring on a patch of narrow-leaved mountain mint near Herrontown Woods. I was treated to a surprising display of butterfly aggression, as several skippers suddenly ganged up to chase the monarch away from the mountain mint. 

Part of that competitive fervor may have to do with the scarcity of pollinator plants. In a 4.5 acre field, there were only two small patches of mountain mint. Since forests don't supply summer nectar, meadows like this are where monarchs and other pollinators are going to find food and each other. Many meadows and roadsides are being taken over by mugwort, Chinese bushclover, and other invasive species with limited utility for pollinators. Add that threat to all the others: habitat loss, climate change, indiscriminate herbicide use in people's yards and along roadsides. This meadow is preserved, but that's really just the first step in realizing the meadow's potential as habitat that can help sustain species like our beloved Danaus plexippus, aka monarch butterfly.

Related posts:

Growing Monarchs

Do Praying Mantises Eat Monarch Butterflies?

Other previous posts about monarchs

Ambush Bugs: Hidden Dangers for Pollinators

During an evening stroll in the backyard garden, with a big show of fireflies soon to come, we were admiring a common milkweed's blooms--like frozen fireworks at lawn's edge--when my friend spotted a honeybee on one of the flowers.

Isn't this the way it's supposed to be? You plant native wildflowers and the pollinators show up to feed ever so gratefully. But something didn't look quite right to me. The honeybee wasn't moving. 

Maybe it was memories of blog posts ten years ago--written after standing for hours gazing at the extraordinarily diverse community of insects and spiders drawn to boneset flowers--that caused me to take a closer look at that motionless honey bee. 

There, beautifully, mischievously, mercilessly camouflaged, hiding between the milkweed flowers, were two pairs of ambush bugs, mottled brown, black and white. The smaller of each pair sat atop the larger, apparently mating. Life is short for an insect, so it seems perfectly practical that one of the females, needing nourishment for whatever eggs come of the mating, had chosen that moment to snag the honeybee whose bad luck it was to visit those particular flowers.

Later, I returned to try for a better photo of the ambush bug and its mate.

By then, they had consumed what they wanted of the bee, dropping the remains to land ever so lightly on a leaf, one story down in the tower of milkweed.

Afternote: One could probably spend a lifetime exploring the mechanisms behind the camouflage of an ambush bug, as this quote from the Missouri Department of Conservation website shows:

"The colors of ambush bugs are worth mentioning. They can vary quite a bit within a single species. Most are gold, yellow, leaf-green, tan, brown, or white, often with dark mottled patches or bands. Apparently males are often darker or more spotted than females. It’s not clear whether individual ambush bugs change color like chameleons (and some crab spiders) to match the plants they’re resting on, or if they simply move to (or survive on) plants whose colors happen to match their bodies. It could be that they change color with each molt: young individuals, early in the season, being pale green, matching the new foliage of springtime, while older specimens become gold and black in later molts to match the flowers that develop in midsummer. The temperatures during egg stage may also affect the overall darkness of the insects."

Witnessing a Spongy Moth Outbreak Along the Appalachian Trail

I wasn't expecting to run into an outbreak of spongy moths (formerly called gypsy moths) in New Jersey earlier this week. The aim of driving up to the Stokes State Forest near Delaware Water Gap was to drop off my younger daughter Anna so she could resume her thru-hike on the Appalachian Trail. 

After a couple day visit at home, Anna was eager to continue her journey northward towards Maine. When we reached Sunrise Mountain Overpass, she asked if I wanted to hike along with her for a bit. 

It was as if she had invited me into her home, which the AT has been since she began in Georgia back in late February--more than 1000 miles thus far. Everything she needs is in her backpack--designed to be lightweight but still very substantial--as she hikes up and down mountain after mountain, rain or sunshine, cold or hot, following America's verdant eastern spine through North Carolina, Tennessee, Virginia, West Virginia, Pennsylvania, and now just the northwestern tip of NJ before heading into New York state. 

Most of the inspiring vistas she sees along the way are not tempered with a warning about venomous snakes, like this one at the parking lot. New Jersey is unusual in having venemous snakes in the north and south of the state, but not where we live in central Jersey. As for black bears, over three months she has seen only one and heard another. Though she started the hike on her own, there's now a group of companions with whom she camps each night.

As we hiked the rocky trail, we had to look mostly down to avoid the stones, stealing glances at the high quality woodland, free from invasive plants except for an occasional garlic mustard. We soon became aware, however, of an odd noise that sounded like a light sprinkle, despite the clear sky. When I turned back, leaving Anna to head north on her many steps towards Maine, I started taking a closer look at the leaves of oak, sassafras, and maple above. The well-munched leaves were surely a very generous giving of tissue by the trees to the local insect population. 

But what was that sound of rain with no rainclouds in sight? And why was the ground littered with fragments of green leaves? Whatever was eating the trees was being messy about it. 

Then I felt something very light fall on my head. I brushed it onto my hand, gave it a good look, and decided to call it frass, that is, caterpillar droppings. 

On the ground all around, the leaf litter had been in turn littered with this frass, raining down from far above.

Though most of the caterpillars remained unseen high in the canopy, a few were close enough at hand to get a photo. 

Back home, searching the internet, the caterpillar's identity quickly became apparent: spongy moth, also known as Lymantria dispar dispar, and formally known as "gypsy moth."

One source described exactly our experience along the trail:

"(Spongy) moths are invasive insect pests that can be destructive to trees, especially hardwoods like oaks. In May and June, each caterpillar can grow up to two inches long and consume 11 square feet of leaves. Signs of a (spongy) moth outbreak include bare tree canopies, droppings that sound like rain, and leaf confetti on the forest floor."

If you haven't heard of spongy moths, or haven't heard of them in a long time, it's because this highly destructive introduced species is no longer causing widespread havoc in our forests. thanks to the development of a remarkably successful, low-toxicity treatment. 

Imported into Massachusetts from Europe in 1869 with the intent of starting a new silk industry in America, the spongy moth escaped into the wild and was soon causing dramatic defoliations of forests. Though oaks are a favorite, spongy moths threaten a broad range of species, including both hardwoods and conifers. One source alphabetically describes its diet this way:

Preferred: Alder, apple, aspen, basswood, birch, hawthorn, oaks, tamarack, willow, witch hazel
Intermediate: Beech, dogwood, elm, hemlock, maple, pine, Prunus species, serviceberry, spruce, walnut
Avoided: Ash, balsam fir, cedar, red & white, locusts, mountain maple, pine, scotch

According to numerous articles found on the Papers of Princeton website, 13 years of intense spraying led to eradication of the spongy moth in NJ by 1932, but it reappeared in 1953 and by 1955 had again become a serious pest. In 1965, a small area near Mt. Lucas Road in Princeton was sprayed. As defoliation increased statewide through the 1970s, the most common treatment--carbonyl, also known as Sevin--became suspect due to its effect on honeybees. 

Letters to the editor describe heroic citizen efforts to round up and destroy the moths' egg cases. Elizabeth Carrick, chairman of the Woodfield Reservation Committee, described a successful outing by girlscouts in 1972. In 1980, Preston and Helen Tuttle reported on a hand collection campaign in the Institute Woods that included renowned faculty at the Institute for Advanced Studies:

During the past two weekends. 95 individuals, ranging from Girl and Boy Scouts to world-famous mathematicians, took part In all. 8.791 egg cases were collected or immobilized witn a hand held sprayer containing a mixture of creosote, turpentine and transmission fluid This was used to spray those egg masses that were above convenient scraping and collecting reach Egg masses collected the first weekend were given to the state Biological Controls Laboratory to feed spongy moth predators being developed by the state.

Destruction peaked in 1981, when 12 million acres were affected by defoliation nationwide. The biggest reason we haven't heard much about this hugely destructive pest lately is the utilization of a low-toxicity bacteria called Bacillus thuringiensis (Bt). First mention of it in local papers appears to have been in 1974. Bt is sprayed on foliage in the spring. When eaten by the caterpillars, it disrupts their digestive systems. By 1990, arborist Sam deTuro of Woodwind Associates, who used to have a regular column in the Town Topics, was combining the traditional chemical spray methods with a new formulation of Bt.

Like the many mountains and valleys of the Appalachian Trail, moth numbers have risen and fallen dramatically through the decades. Spongy moth numbers in NJ reached a relative low in 1988, only to rise 19 fold in 1989. Another peak came in 2008, prompting aerial sprays of Bt in Princeton. 

Numbers have dropped since then, leading many of us to forget about spongy moths altogether. For that luxury, we have a state government program to thank. The New Jersey Dept. of Agriculture has been running a   spongy moth suppression program at least since 2007. In 2024, they planned to spray 3000 acres of local and state-owned land. The aim is to prevent repeated defoliation of forests. Trees that can survive defoliation one year may not be able to survive defoliation two years in a row. The state description sounds like what governments are supposed to do--work collaboratively to intervene in safe ways to protect us and our environment. LDD stands for the species name, Lymantria dispar dispar.

The New Jersey Department of Agriculture promotes an integrated pest management approach, which encourages natural controls to reduce LDD feeding and subsequent tree loss. However, when LDD cycles are at a peak, natural controls have difficulty in preventing severe defoliation. In these special cases, the Department recommends aerial spray treatments on residential and recreational areas using the selective, non-chemical insecticide, Bacillus thuringiensis.

The Department's LDD Suppression Program is a voluntary cooperative program involving New Jersey municipalities, county agencies, state agencies, and the USDA Forest Service.

17 miles down the trail, Anna was still hearing the curious rain of frass all around, Hopefully the state program of spongy moth suppression will continue to work--an all-too-rare example of successful containment of invasive species threatening our forests.

Below, some sights seen during my short hike on the Appalachian Trail:

Expanses of sedge meadow that can give healthy forests a natural park-like appearance.

The striped maple, Acer pennsylvanicum, is a little tree that grows all along the Appalachian Mountains.

If you hike northward on the AT with the spring, much of your journey will be graced with the blooms of Mountain laurel, Kalmia latifolia, abundant on rocky slopes.

Tent Caterpillars and the History of Black Cherry Trees in Herrontown Woods

Black cherry trees draw attention in early spring because of the "tents" that tent caterpillars weave on them. I was surprised to find out that these tents are sometimes mistaken for gypsy moth infestations. There's also some disagreement as to how damaging tent caterpillars are to the trees they feast upon, so I decided to do some investigation. 

First, some distinctions between tent caterpillars and gypsy moths. Tent caterpillars are native, feed primarily on cherry trees, build conspicuous tents, and do their feeding on the fresh, tender leaves just beginning to emerge in April. Gypsy moths are a nonnative species imported from Europe, start feeding in May on a very wide spectrum of hardwoods and even some conifers, and do not build tents. 

Gypsy Moths

The story of gypsy moths in our area is most easily grasped by looking at how many articles about them have been archived in the Papers of Princeton through the decades. Outbreaks of gypsy moths remained minor in New Jersey until the 60s, then grew into massive defoliations of forests in the 1970s. By the early 1980s, gypsy moth populations were beginning to drop, thanks to a natural virus, introduced parasites, and aerial sprayings. A naturally occurring bacteria called Btk proved safe and effective when sprayed on trees where gypsy moths were feeding. There was a recurrence from 2007-8, but numbers have dropped off since then. Though the forests largely healed, the trauma of past gypsy moth infestations lives on in people's memories. 

Tent Caterpillars

What we have this spring, and springs extending back through millenia, are native tent caterpillars making their tents. 

Some sources on the web suggest that tent caterpillars, despite the powerful visual of the tents and defoliated branches, don't do enough damage to a tree to worry about. I'd really like to believe that, but this young black cherry tree, now bearing eleven tents from which the caterpillars make forays, is almost completely defoliated. 

They say a tree can survive one complete defoliation, but if defoliated several years in a row, it becomes increasingly susceptible to disease and insect attack.

Meanwhile, our very hungry tent caterpillars have even followed a branch over to a neighboring pin oak, which now, too, is getting chowed down upon.

We pause to note a couple recurring themes in nature. One is that the tent caterpillars will shift to a less desirable food source (a pin oak tree) if their favored cherry tree leaves run out. Deer, too, will begin eating less desirable foliage if they run out of their favorites. Thus, an overabundance of deer in the 1990s almost wiped out spicebush in our Princeton woodlands, despite it being low on the list of deer's preferred foods.

The other example of a recurring theme in nature is that the tent caterpillar eats only one crop of leaves, then is done for the year, allowing the tree to recover. The worst thing a predator could do is be so effective as to eliminate its prey. 

The introduction of a new insect, though, could throw off this balance of predator and prey. If another insect, say, a gypsy moth, came along and defoliated the same tree yet again in the same growing season, that tree would be in big trouble, having twice committed energy to manufacturing a whole crop of leaves, only to have them eaten. One question is whether the gypsy moth outbreaks in the '70s and '80s killed more of one tree species than another, causing changes in forest composition still noticeable today.

There's a lot of caterpillar behavior whose purpose is not immediately obvious. A week ago, caterpillars were crawling about on the outside of the tent, turning this way and that. My best guess was that they were expanding the tent by adding another layer of silk, but no strands could be seen coming from their bodies as they moved about. 

And why are these caterpillars clustered on the side of the tree, outside of their protective tents? Wouldn't they be easy picking for the birds that are said to consume them? 

As their spring residency has continued at the Barden in Herrontown Woods, the tent caterpillars have spun not only isolated tents but also enveloped the trunk and limbs in a silken web reminiscent of the webbing people drape on their shrubs for Halloween. A closer look reveals that the caterpillars have spun silken highways upon which they commute from tent to the "pasture" of the canopy. These highways are only one lane wide, requiring a caterpillar to temporarily step aside if it meets another coming the opposite direction. Some silken highways are suspended in air, like overpasses--a great way to smooth out the rough terrain of a black cherry tree's "black potato chip" bark. 

A tree colonized by tent caterpillars, then, has elements of occupancy, transport, and exploitation not unlike the human footprint on the land, with our homes, highways, and farm fields. A big difference being that the tent caterpillar's settlement is seasonal--more like the impact of nomadic tribes than our permanent villages--giving the tree a chance to recover.

Another big difference between tent caterpillars and other builders of shelters--bees, ants, birds, mice, people--is that the caterpillars don't seem to bring anything back to the shelter other than their bigger, well-fed selves. They aren't adults bringing food back to the young. The caterpillars, like super resourceful children, work collectively to raise themselves, then leave the tree on their own to pupate and turn into adult moths. 

A nice writeup about tent caterpillars (Malacosoma americanum) found at ThoughtCo.com states that the broad side of the tents faces the sun, and that the caterpillars make three forays per day, returning to their tents inbetween. That will be something to check out next spring.

Surprisingly, the subject of wild cherry trees in what is now the Barden (formerly a pine plantation) came up more than 50 years ago, in Richard J. Kramer's book about Herrontown Woods. 

"Wild black cherry, which grows to magnificent size in the Allegheny Mountains, is a poorly formed tree in Herrontown Woods, occurring mostly in areas which were recently open fields. Its best growth has been in the pine plantation, where specimens are 30 to 40 feet tall and possibly may develop into good-sized trees. Apparently these black cherries were able to develop along with the young pines after these were planted in the open field. Although the birds do bring seeds of the cherry into the forest, the many seedlings and the few saplings that occur there grow poorly and remain shrub-like."

Gone now are most of the pine trees in the pine plantation, and those larger cherry trees are nowhere to be found. Our 12 little black cherry trees in the Barden, all saddled with tent caterpillars, must be the descendants of the larger cherry trees Kramer describes. Only one large black cherry tree is known to exist now in Herrontown Woods, almost completely free of tent caterpillars, growing next to Veblen House. Have tent caterpillars contributed to keeping the black cherry trees of Herrontown Woods from achieving full size, in the past as well as in the present?

If we wanted to relieve the cherry trees of the spring burden of hungry caterpillars, we could remove the tents and remember to crush the egg masses laid by adult moths on small branches in late summer, as suggested in this useful post about the insect. 

But as insect numbers continue to decline, the role of trees as food for native insects grows in importance. And if the cherry trees remain small, that will allow more sunlight to reach the many wildflowers growing in the Barden. Leaving the tent caterpillars to grow undisturbed can serve as an experiment, to see if they continue to flourish year after year, or if nature's array of predators, pathogens, and parasitoids finally up their game and reduce the burden these trees now bear.

The Lost Forest of Rogers Refuge

This past November, I received a request to look at a lost forest in Princeton. 

The request came from what may be the oldest open space organization in town--the Friends of Rogers Refuge. Dating back to 1967, FORR has been working with the town, and the water company that owns the land just down from the Institute Woods, to sustain the refuge's role as premier habitat for a tremendous diversity of birds.

Over the years, I've been able to witness and collaborate with a progression of leaders who have overseen stewardship--the Southerlands, Tom Poole, the Spars, the Varians, and most recently David Padulo. 

At annual meetings, discussions have tended to focus on the refuge's central feature, the surprisingly extensive marsh--how to keep it wet enough and protect it from the super-aggressive Phragmitis.

But this year, concern now extends to the floodplain woodlands surrounding the marsh--also vital bird habitat. One of these woodlands, thriving four years ago, has lost its trees.

This was not a forest classically lost to logging. The trees were not cut down but rather strangled over the course of several years, then left standing, each tree a monument to its past life. 

Few have seen the now ubiquitous strangler, the Emerald Ash Borer accidentally introduced to the U.S. from Asia. It's larvae work quietly under cover of bark, feasting on the ash trees' circulatory tissues. 

That a whole forest could die speaks to how common ash trees once were. The most numerous tree in Princeton up until just a few years ago, comprising more than 10% of the tree cover, the ash tree's skeletons can be found throughout the canopy of residential and open space lands. Ash were particularly good at colonizing abandoned fields, to the point of dominating one area of what is now Rogers Refuge. 

As the botanist in an organization of birders, I was asked what the longterm prognosis for this lost forest might be. Winnie Spar, Joe Melton, and I walked the red trail to have a look.

One striking feature is what I call "poison ivy trees." These are dead trees, still standing, that have been scaled by poison ivy vines, with their classic "hairy is scary" stems. In order to bloom, poison ivy must climb a tree, sending out lateral flowering shoots along the way. The branch-like laterals give the tree the look of still being alive, even though all the leaves are now poison ivy. The flowers produce berries that, birders will enthusiastically tell you, serve as important food for birds.

Another feature of a lost forest is the shrub growth that now thrives on the infusion of sunlight previously claimed by the tree canopy. Much of this shrub growth, unfortunately, is nonnative and inedible to wildlife, like this Asian Photinia. At least it can be said that the invasive shrubs are not as thick at Rogers Refuge as they are at the Institute Woods just up the hill.

A few other native tree species fill a small portion of the void. In early November, the occasional silver maple and pin oak still had many of their leaves. Mixed in were a couple elms, and a red maple. 

Used to the numerous red maples at Herrontown Woods on the other side of town, I was surprised to find instead an abundance of box elder of every size growing in this broad floodplain of the Refuge. Related to maples, box elder are not the most statuesque of trees, but their soft wood can make good bird habitat. They now stand as the main hope for rebound in this patch of former forest. 

The walk being with such knowledgeable birders, attention never strayed far from bird life. We saw a couple pileated woodpeckers, a coopers hawk and a couple other larger hawks. Winnie kept up a running monologue about the status of this or that bird. Mockingbirds have been around for a long time, but the catbirds keep them out of their territories when they are present. While a warming climate is causing many birds to extend their ranges northward, ravens, surprisingly, are moving south. She's seen some in the Refuge. Warblers love something about the spicebush flowers, whether it's the flowers themselves or an insect in them. Blue gray knatcatchers were mentioned, along with many other bird names that didn't register in my botanical brain.

There's a lot of concern that last year's fires in Canada have been very hard on migrating birds that nest up there. A woman who catches and tags migrant birds had been having very few birds coming back down from Canada, but her catch/tag/release activity, conducted on Sundays, was hampered by rains every weekend this fall. One day she got only ten birds, total. 

But then Winnie is quick to add that she saw Cape May Warblers in the Refuge for the first time, several in fact, with immatures, and they too nest in Canada. Winnie is one to accent the positive, while acknowledging that migrant bird numbers are down 50-90%. 

This lost forest, the decline in bird numbers, accelerating changes in climate, democracy under threat--in many ways, America is losing its memory of what it once was. The soil, for its part, holds memory through the seeds that remain dormant within it. Back when the seed bank--this stockpile of seeds yet to sprout--was dominated by the seeds of native species, succession as an ecological phenomenon featured an orderly and predictable progression of species, from grassland to shrubland to mature forest. But the soil under our feet has lost its memory, whether by plow, development, intense browsing, or displacement of native species. Invasive lesser celandine, poisonous to wildlife, coats the ground in the spring, followed by inedible stiltgrass and its billions of seeds in late summer. Invasive shrubs and deer combine to limit native species and thwart the once timeless process of succession. Though the tree canopy is still dominated by natives, these are under increasing attack from introduced insects and disease.

Even healthy trees can be overwhelmed by vines of porcelainberry and wisteria.

Given the circumstances, it's fair to ask what sense there is in persevering. What I find is that the native growth force, if often smothered and badly abused, remains intact. When given a chance to prosper, native plants and wildlife still can thrive. In Rogers Refuge, we've seen a tremendous rebound of spicebush since the town began culling deer to reduce browsing pressure. That in turn has improved habitat for birds. FORR has paid contractors to successfully set back the Phragmitis and porcelainberry. 

Through periodic interventions over a number of years, the Varians have virtually eliminated the one patch of invasive Japanese knotweed at Rogers Refuge. 

We pick our spots, time our interventions strategically to have the most impact for the least amount of effort, and look for opportunities. Despite the tragedy of losing ash trees, the new openings in the canopy could potentially allow native shrubs to grow, flower and bear in ways they haven't since being shaded out decades ago. 

Our inherited environmental mindset is that nature, if protected from intentional depredations like logging and draining, will heal itself. As FORR's webmaster Laurie Larson points out, "when Charles H. Rogers and the Southerlands started birding the “Water Company” in the 60s and 70s it was a landfill." The initial fight was to put an end to dumping. But now, at Rogers Refuge and many other places, the main depredations (invasive species, climate change) are unintentional, and the healing must be helped along by intentional effort. That effort could seem a sacrifice, but the primary feeling is one of gratitude, for the chance to work with nature--the greatest and most generously creative collaborator of all. 

Where Have All the Spotted Lanternflies Gone?

Well, it's happened, at least in our neck of the woods.

Billed as a major calamity, the spotted lanterfly invasion has gone "poof" this year. Yes, the spotted nymphs could still be found clinging to the stems of Ailanthus sprouts at our Barden in Herrontown Woods. 

And a few adults were later seen perched on the rachis of Ailanthus leaves. We pulled the sprouts out of the ground to deprive them of this haven. Hard to say where they went after that.

Writing a post about lanternflies three years ago, I learned that numbers of the invasive insect had dropped in some areas of Pennsylvania five years after first being seen. Lanternflies first showed up in Princeton in 2018, and here we are five years later, with what appears to be a dramatic drop in numbers.

It's true that people gave themselves over to squashing the pesky bugs--leafhoppers, actually--in spirited ways. (This photo shows one of the more creative approaches.) Some think the unusual weather has had an effect. Insect numbers overall have been down, be it the pollinators on backyard flowers, the odorous house ants that used to invade our kitchen, or spotted lanternflies. But my guess is that it has been the full-time predators, feathered or with eight legs or six, that are to be most congratulated for stemming the explosion of spotted lanternflies. 

Just follow the trail of colorful wings that brightened a walk up towards Veblen House one day.

The most powerful contrast for me is between the invasions of emerald ash borer and spotted lanternfly. Since the emerald ashborer arrived, about ten years ago, I have yet to see a single adult ash borer in Princeton, and yet the devastation they have brought to the ash tree is all around us. The lanterfly, on the other hand, has been seen everywhere, and yet I can't point to a single plant that has died due to their appetites. We humans are visually oriented, but it's the invisible threats--be they an invasive insect or even more significantly an overdose of carbon dioxide--that most endanger our world.

Four Kinds of Honey Bees in Northern Thailand

These bee hives look like something Winnie-the-Pooh might stick his paw into. The hives are made of hollowed out sections of tree trunk. The photo was taken by my daughter Anna, who was traveling this summer in southeast Asia. 

To escape the heat, she and her boyfriend headed up into a mountainous region in northern Thailand called Chang Rai, where the residents drink three kinds of tea and grow four kinds of honey. She was surprised to learn that the black, green, and white teas all come from the same plant--the same species of tea. But the four kinds of honey are not made by the same kind of bee. This is four kinds of honey made by four species of bees. Thailand, it is claimed, has the greatest bee diversity in the world, including half the world's species of honey bees, and in this tiny village the various honeys they produce are an important part of the diet. 

There's the honey we're familiar with, and then there's another one that tastes like apricot jam. A third, produced by the stingless bee, has a fermented fruity flavor like Kambucha. 

Another species, the asian giant honey bee (Apis dorsata), can't be kept in a hive, so villagers climb trees to reach the honey. Wooden footholds are placed in the tree trunk to expedite the climb. The giant honey bees don't stick around all year, but instead migrate up to 200 kilometers, returning to the same branch six months later.

The asian honey bee (Apis cerana) produces less honey than our honey bee, but is much easier to take care of. 

A Brief Account of Life in a Mountain Village in Thailand

Their first night in the village, they were surprised to be awakened at 3:30am by the robust crowing of roosters, so raucous that the whole village has little choice but to rise and begin its day. Chickens run loose, apparently free of local predators that might consume them before people have a chance to. Once a year, a tiger passes through the area, apparently without raising much concern.

The town runs on solar energy, but lest one think this mountain village an idyllic integration of humanity into nature, daytime brings cooking fires and the burning of refuse. The villagers are conditioned to the resulting stew of smoke that can linger in the valley, but it registered as noxious and toxic to Anna. 

Some of the refuse is plastic, which we're all told releases toxins when burned. What plastics do the villagers have if they grow their own food and have few possessions? Though they cook delicious meals most days, there are times when villagers may not feel like cooking, and so pull out store-bought noodles and tomato sauce, the plastic wrappings from which end up getting burned in the refuse pile. 

This is not much different from my own experience growing up in a small village in Wisconsin in the 1960s. One of my chores was to burn the garbage, plastic and all. In autumn, we'd rake some leaves into piles to jump into, and others into piles to burn. We'd toss acorns into the glowing core of the fire and wait for the popcorn-like explosion. On brisk, sunny fall days, the whole village became suffused with what registered as a sweet and endearing aroma of burning leaves. Even after moving to a city, the 1930s house we moved into had an incinerator in the basement for burning trash. And in the 70s and 80s, when I played jazz gigs in smoke-filled bars, it was not until the next morning that I'd notice the wretched smell of stale smoke in the clothes I had worn. 

There have been efforts to promote cleaner air in remote mountain villages around the world. Some students, before entering Princeton University, sign up to spend a "bridge year" in a foreign country doing good deeds, one of which is helping build cleaner burning stoves for villagers in Peru and elsewhere. You'd think the villagers would be grateful for a home less choked with smoke, and maybe they are, but the capacity of the body to become conditioned to abuse is both impressive and exasperating.

Lots of interesting reading out there on bees. Here's some info about eight species of honey bees around the world.

Monarch Butterfly Update -- July, 2023

How many monarch butterflies are people seeing this year? I've seen a grand total of two thus far. Neither paused for a photograph, so this picture is from a past year. 

On July 11, I saw one flying crazily at the Barden. They are expert and often seemingly whimsical flyers, but this one's flight was unusually frenetic. At double the usual pace, it would approach flowers but not land on them, leading me to speculate that it was looking for a mate rather than nectar. A useful Q&A post at JourneyNorth.org suggests that these episodes of particularly erratic flight are induced either by a predator's attack or by a male chasing a female. But the frenetic flight made me instead imagine what it is like for monarchs when their numbers are few, and the search for a mate consumes more and more of their energy. Might a fruitless search at some point become frantic?

A few days later, I saw a monarch in a pasture near Herrontown Woods, flying at a more measured pace. 

There were a few common milkweeds growing in the pasture, but I was particularly happy to discover a couple specimens of green comet milkweed (Asclepias viridiflora), growing there as well. It's a species I've only seen twice in Princeton, the other incidence being a few individuals in the Tusculum grasslands. 

It's common to think that monarchs gain all their sustenance from milkweeds, but in fact the adult butterflies obtain nectar from a broad range of flowers. Otherwise, they would starve after the milkweeds have finished blooming. The caterpillars, however, are highly particular, and will only eat the foliage of milkweeds. The milkweed foliage is around all season long for the munching, though a lot has to happen for the foliage to actually be put to use. A female needs to lay eggs, and those eggs need to elude predation long enough to hatch. I have not seen an actual caterpillar in years, nor much evidence of milkweeds being consumed, but clearly a few are surviving somewhere.

To get a more in-depth report on the status of monarchs, my go-to is the savant Chip Taylor, who blogs at MonarchWatch. In a June 14 post, writing about whether monarchs will be listed as threatened or endangered, Chip Taylor wrote openly about the eventual end of the great monarch butterfly migration. It's believed that the monarch itself is not likely to go extinct, but that the migration--involving the portion of monarchs that participate in the fantastic journey north from the mountains of Mexico up into the U.S. and Canada, then back to Canada in the fall--is increasingly vulnerable. According to Taylor,

"As applied in this case, extinction refers to the loss of the monarch migration and not the species per se. Given the link between the increase in greenhouse gas emissions and increasing temperatures and the world’s slow response to these changes, yes, the monarch migration will eventually be lost."

It's important to note that those who raise alarms about the climate crisis are the optimists. It is optimistic to face up to a grave risk, and call for action to save what will otherwise be lost. Denial and dismissiveness are rooted in pessimism. They take a gloomy view of 1) our capacity to recognize dangers and 2) our capacity to act collectively to prevent catastrophe. Taylor's recognition of the high likelihood that we will lose the migration raises an obvious question, which he hastens to answer.

"If the monarch migration will be lost eventually, why make great efforts to sustain it? Faith. We have to have faith that the world will come to its senses and work collaboratively toward the reduction of greenhouse gases to save the natural systems that sustain us. There is hope. The rate of increase in CO2ppm has declined in recent years."

Another answer is that, the longer the migration can be maintained, the longer humanity has to "come to its senses." 

It is stunning, knowing the extraordinary power of carbon dioxide to influence the earth's climate, that society has left it unregulated. As individuals, cities, and businesses, we remain free to pour as much of it as we please into the atmosphere. Until that giant hole in our regulatory protections is patched, the vast majority of people will not change their behavior.