Authors Posts by Matt Pelikan

Matt Pelikan

Matt Pelikan
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Tachinids are essential to human society

Not just another housefuly: It's hard to tell one Tachinid from the other 10,000 (or more) Tachinids. But they're all crucial to human civilization. – Photo by Matt Pelikan

This column is about some of the unsung heroes of the insect world. While you’ve almost certainly seen one, you’ve likely never heard their name. But without their role in controlling numbers of other insects — and I mean this quite literally — human society would have a hard time functioning.

I mean the myriad members of the fly family Tachinidae (most entomologists pronounce it “tak-IN-adee”). Tachinids, as they’re called, are numerous, diverse, and highly variable flies. Some 10,000 species have been described worldwide, and many tens of thousands more are surely out there, waiting for someone to notice their existence.

Flies, including tachinids, are hard to identify; pretty much all of the dozens of fly families have some members that look like your basic, generic fly: gray, hairy, and sporting no traits that stand out as distinctive. While there are certainly many distinctive flies, even experts can have trouble assigning a photographed fly to a particular family. Identification often relies on viewing tiny anatomical details under magnification.

But if I had to pick one feature as a mark of the family Tachinidae, I’d point to their bristly butts: The abdomen of a typical tachinid is well-endowed with strong bristles, and many times this trait is enough to put an unknown specimen into this family. (Actually identifying a tachinid to species, once you’ve recognized its family, is another, often harder task. But students of the insect world get quite comfortable with tentative or imprecise identifications.)

But despite enormous variation in the size and appearance of tachinids, members of this family share one crucial life-history trait that gives this group its importance: The larvae of tachinids (I’m trying to avoid the word “maggots”!) are parasites on other species of insects. From an egg laid on or near a suitable host, a tachinid larva hatches and, if it’s lucky, succeeds in burrowing into its host. Maturing inside the unfortunate victim, the tachinid develops by eating the living tissue of its host, and when mature, it eats its way out, finishing its maturation in another location but leaving behind a dead host.

Within this enormous family, there are countless variations on this basic theme. Some tachinids are highly host-specific, using just a single species or genus as their larval host. Others are quite ecumenical in their tastes, laying eggs on a wide range of victims. Immature flies use different methods of entering their hosts: some chew their way in, while others may be ingested (even while still in egg form) as their hosts-to-be feed. Many adult tachinids, much more genial than their larvae, visit flowers to eat pollen (helping pollinate the flowers they visit as a side effect).

Because a single female tachinid can lay dozens of eggs, and each egg is a potential assassin, these flies can exert a powerful downward pressure on the populations of their hosts. And a sort of feedback loop can amplify this effect over the course of a few generations: If a host species increases in number, more Tachinid eggs find their target, producing a much larger next generation of flies. Often with just a generation or two, the flies have parasitized their excessively abundant host back down to normal numbers.

While many types of insects (and even, occasionally, other types of arthropods such as millipedes) can host tachinids, as family these flies focus mainly on Lepidoptera — that is, on moths. Many moths have larvae that eat plants of concern to people (crops and ornamentals); and many moths are capable of staging huge population explosions (think of gypsy moths or the winter moths that have helped defoliate large tracts of Vineyard woodland in recent years). Tachinids are not the only things that control such outbreaks, but they can be among the most effective. Without the regulating role of these flies, human agriculture and horticulture would be far more difficult undertakings.

Tachinid flies are sometimes deliberately deployed as “biological controls” of problematic insects such as invasive moths introduced to new regions, away from the effect of the predators of their native range. While a few ecological catastrophes have resulted from well-meaning introductions of tachinids, with the flies decimating desirable species once they’ve brought their original target under control, biologists have learned a great deal from such situations. As more and more invasive insects get established around the world, the use of tachinids to control them will likely be an increasingly frequent human response. One tachinid, Cyzenis albicans, is currently being used (with promising results and no discernible bad effects) to control the invasive winter moth in our region.

I have no real sense of how many tachinids live on the Vineyard — certainly hundreds of species, maybe many hundreds. But members of this family turn up everywhere I go. You’ve probably mistaken some for common house flies. But in doing so, you’ve overlooked an important ally.

 

In the bird world, there’s a lot more to consider than looks and talent.

An Eastern phoebe. – Photo courtesy of Wikimedia Commons

The past week, featuring warmer weather and — at last! — the obliteration of most of the snow on the Island, saw a huge change in the bird life of the Vineyard. Sea ducks, after a winter in our waters, headed north in droves to breed. And on land, a strong wave of early songbird migrants hit our shores.

Among these was one of my personal favorites, the eastern phoebe. Drab birds, smaller than a robin and belonging to the flycatcher family, all our phoebes generally arrive almost at once: just a few days after the first report of the spring, virtually all of our breeding phoebes are here.

Flycatchers as a group are among the dullest songbirds, and the eastern phoebe, grayish brown on the back and off-white underneath, is dull even by flycatcher standards. You might say that the lack of distinct field marks is the most reliable field mark for this bird — though its habit of bobbing its long tail up and down is a valuable behavioral clue. To my eye, a phoebe glimpsed quickly has a faint yellowish cast; this is a subtle and perhaps illusory trait, but a useful one for a birder. Overhead, a phoebe shows rather squared-off wings and a narrow-based tail with a distinct notch at the end — again, subtle but reliable cues to the bird’s identity.

Still, you’re more likely to hear your first phoebe of the year than to see it. These are chatty birds, often giving a sharp “chip” note and singing (if that’s what you call it) from the moment they arrive: a sneezy “PHEE-bee” is the best this bird can manage. But it’s a welcome sound in late March or early April. While the bulk of the singing is done by the male, I believe that this is a species in which the females also sing.

More so than nearly any other bird, the phoebe tolerates, or even prefers, life around humans. The species originally nested, and sometimes still does, in wholly natural settings, building its mossy nest on a rocky ledge or at the base of a tree branch. But when humans began building barns, sheds, and houses in the phoebe’s world, these birds were quick to recognize an opportunity. These days, a typical phoebe nest is tucked up tight under the eaves of a human structure, safe from the weather.

A pair of phoebes often starts multiple nests, sometimes getting them all well along toward completion before deciding which one to lay eggs in. This habit may help fool would-be nest predators, and in a seasonal human community like the Vineyard’s, it may give the birds some flexibility in adjusting to changing patterns of human activity as the season progresses: if the frequency of disturbance around one nest gets too great, the birds simply forget about that one and focus on a nest in a quieter spot.

The arrival of these birds seems to coincide quite precisely with the first real blooms of insect life, often in the form of swarms of ephemeral flies. But as the spring advances, phoebes show remarkably varied tastes in their insect prey. As with most flycatchers, phoebes prey heavily on bees and wasps. But studies of their diet have shown that they happily eat beetles, flies, and moths, with even the odd tree frog or salamander thrown in. They’re also able to handle vegetable food, mainly berries — an ability that helps them survive if they’re caught by unexpected wintery weather.

Most of a phoebe’s prey is taken on short aerial sallies: The bird perches on a twig, locates its target by sight, launches its attack, and often nabs its prey on the first attempt. The bird’s bill, broad with a distinct hook at the tip, is a formidable cruncher of bugs. But phoebes also pick food — spiders, or insect eggs and larvae — from branches or structures, and they will even forage on the ground, tossing dead leaves aside to search for arthropods.

Phoebes enthusiastically try again if they lose their first clutch of eggs, and if they fledge their first set of young, I believe, they’re capable of pulling off a second brood. Our nesting phoebes will be with us into the early fall, with adults leaving before the young of the year. And while we don’t get many transient phoebes here in the spring, fall migration can bring large numbers of phoebes from farther north. The species continues to pass through well into October, and a few individuals even try to winter in our region, with some surviving until spring at least in mild seasons.

Their ecumenical diet means that phoebes eat many insects that humans consider beneficial. But they eat harmful insects with equal zeal, and like most insectivorous birds, they adjust their diet to take advantage of any prey species that gets especially common. So the phoebe is a powerful force for balance, tending to regulate insect populations. This makes them helpful birds from our perspective, and if you have a pair nesting on your house shed, consider yourself fortunate.

 

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Springtails are relatively unknown, but not unimportant.

If you see insects jumping in the sand, they're probably springtails. But they're not insects. – Photo by Ab H. Baas

Here’s another column on an important group of animals that you’ve probably never heard of: the springtails (Collembola to biologists). Tiny and six-legged, springtails are superficially similar to insects, and in the past have sometimes been treated as an order with the class Insecta. But the current view elevates Collembola to a class of its own, a separate lineage that diverged from insects some 400 million years ago, retaining primitive traits from a shared ancestor while the insects evolved more complex forms.

Springtails have simpler bodies than insects, with fewer segments to their legs and abdomens. They lack the external mouth parts of an insect. And critically, they lack any sort of respiratory system; oxygen enters their bodies by diffusing through their “skin.” As a result of this primitive means of breathing, Collembola are necessarily small; diffusion can’t supply oxygen to a large body, and most springtails are only a millimeter or two in length. And because the body covering needs to be permeable to oxygen, it’s permeable to other things, as well, such as moisture: Springtails are largely restricted to moist environments because they’re at constant risk of dehydration. (They’re also vulnerable to insecticides and other toxins, which can readily be absorbed into a springtail’s body.)

Despite these limitations, Collembola occur widely, including on the Vineyard, and are often mind-bogglingly abundant. Along with another primitive life form, the roundworms or nematodes, springtails are considered to be among the most numerous animals on earth, many billions of tiny organisms adding up to a huge amount of living tissue and, therefore, major ecological importance. Collembola live in damp soil, on decaying wood, or sometimes in crevices on tree bark; they live by eating bacterial and decaying organic matter. Operating at such a small scale in moist environments, springtails are in constant contact with fungi, and their most important ecological role is helping spread the spores of fungi, including beneficial ones that form vital partnerships with plants. Without the direct and indirect actions of springtails, the natural world would be a distinctly less fertile place.

Most springtails (here’s how they get their name!) have a spike-like organ, called a furcula, extending from the tips of their abdomens. The furcula normally bends forward under the animal and locks in place against the body, but it can be put under tension and then released: As it snaps straight, the furcula launches the whole springtail into the air. The animal has little or no control of where the furcula will send it, but these leaps are dramatic and help a springtail avoid disturbance or predators. If you encounter a swarm of tiny, leaping, insect-like critters in early spring, odds are good you’ve found some springtails.

On a mild day a couple of weeks ago, I rummaged for signs of life in a narrow strip of litter, exposed as the snow melted, along the walkway in front of my office. A beetle larva, the nymph of some kind of roach, a crab spider … and finally, a tiny, gray object, perhaps two millimeters long, that popped into the air and landed on a flagstone. My first springtail of the season!

The tiny size of the animal challenged the abilities of my camera, and bad photos were all I could manage. But comparing the shots I took to better photos on the Internet, I concluded that I had found the common and widespread springtail Tomocerus vulgaris (like most obscure arthropods, it has no common name). It’s only the second species of Collembola I’ve found on the Vineyard (but then, I’ve barely looked); the other, Hypogastrura nivicola, is commonly known as the snow flea. Even more resistant to cold than most springtails, Hypogastrura gets its name from its habit of swarming (sometimes by the thousands) on the surface of snow.

As far as I know, the Vineyard’s Collembola are essentially unstudied. This is not a large group (depending on the source, there are between 3,000 and 6,000 species worldwide), but I’m sure the two species I’ve found represent a very modest portion of the springtails that are here. Very likely, human activity has significantly altered the Island’s Collembola. For example, because these animals can’t tolerate dry, sunny sites, the sheep-farming days of the 19th century, which largely deforested the Vineyard, must have wrought havoc among our springtails. And because of their soft and permeable body covering, springtails here and everywhere surely experiences stress from acid rain and even background levels of pesticides and other chemicals.

And yet, Collembola has felt little need to evolve during the past 400 million years (the oldest fossils and amber-trapped springtails closely resemble modern species). Despite their small size, simple anatomy, and susceptibility to the chemical environment surrounding their bodies, springtails have found a plan that works for them. They’re here to stay.

How wildlife weathers a wild winter (or not).

Barn owl. –Courtesy Wikimedia Commons

Temperatures in the low 40s last Sunday, with a forecast for more days above freezing this week, make it possible to imagine speaking of the winter of 2014-15 in the past tense. This past February ranks among both the coldest and the snowiest months in living memory, and the Wild Side, naturally, is eager to see how this convergence of miseries will affect the Island’s wildlife.

Carolina wren. –Courtesy Wikimedia Commons
Carolina wren. –Courtesy Wikimedia Commons

Everything that winters routinely on the Vineyard, of course, is capable of coping with some measure of snow and cold. And for many of these species, the ones that ride out winter by hibernating, the harsh season will have less effect than one might imagine. Once dormant, many of these species can survive far deeper cold than we’ve experienced. Mortality may be further lessened by the fact the season’s two irritants have worked, in some ways, at cross-purposes. A deep layer of snow serves as thermal insulation, moderating and stabilizing the temperature at and below ground level, where many overwintering insects reside.

Some insects, rather than entering deep hibernation, remain semi-active during winter, rousing themselves to feed and continue their growth during warm spells. For these insects, the most apparent effect of the winter will likely be delay in their life cycle. Instead of maturing and beginning to reproduce in early April, for example, the semi-active nymphs of the northern green-striped grasshopper will not get to work on the next generation until mid-May.

Brown thrasher. – Courtesy Wikimedia Commons
Brown thrasher. – Courtesy Wikimedia Commons

While a species like this grasshopper may not experience unusual mortality from a hard winter, there may still be consequences. Their eggs will be laid later in the season than usual; the weather may be hotter, and the days longer, than eggs or delicate young usually experience, which could translate to more mortality from desiccation. In other words, for some insects, this past winter may have indirect effects that won’t be evident until the next generation has matured.

For animals (mainly warm-blooded ones) that remain active during the winter, the past few weeks may have had profound effects. The insulating effect of snow is largely irrelevant for these animals; far from an advantage, snow cover vastly complicates the process of finding food. Combine that with low temperatures that drain the heat and energy from a warm body, and you have a recipe for stress and, for some species, high mortality.

Among birders, stories have been circulating of birds found dead in unusual numbers, and of unusual species turning up at feeding stations. The brown thrasher, for example, winters here regularly, though in very small numbers; evidently much warier than the related mockingbird, which flourishes amid human landscaping, thrashers generally occupy thickets in areas without much human disturbance. This year, though, has seen many reports of thrashers seeking out feeding stations, clearly driven by harsh conditions to overcome their usual aversion to humans.

How severe the effects are will vary widely from species to species. Barn owls, for instance, are notorious for suffering during rough winters. We are near the northern limit of their range, suggesting that our winter climate is, on average, about as demanding as they can tolerate. Barn owls are capable of successfully targeting their prey (mainly rodents) using hearing alone, which you might think would allow them to nail voles moving in tunnels beneath the snow. But there seems to be a limit to how much snow a barn owl can handle; they may simply not be large or strong enough to plunge through a thick layer. In any case, winters like this one invariably decimate the Island’s barn owls, conceivably even wiping them out entirely and leaving the Vineyard vacant until it is recolonized.

A more obvious avian victim of the winter will probably be the Carolina wren, a tiny brown bird that is ubiquitous in yards and gardens. Again, this is a bird near its northern limit, and it is a species for which significant snow cover apparently poses insurmountable challenges for foraging. Its song will be heard much less often this spring.

From the biological perspective, such high-mortality periods can be significant. The lucky survivors may find life especially easy in coming months, with few competitors for the best nesting sites and food resources. Both the wren and the owl can be highly fecund, producing multiple broods in a season. The result will be reestablishment of normal numbers within just a few years (barring more catastrophic weather) — but in genetic terms, changes may occur in a population growing back from such a small number of founders.

If the survivors benefited from some genetically determined quality, they will pass that on, perhaps producing descendants that are better suited to hard winters. But if it was mainly luck that determined survival, the “founder effect” may crimp the genetic diversity of the species, possibly leaving it more vulnerable to future challenges. So for many resident birds and mammals, this winter will go down as a “bottleneck event,” changing the genetic composition of the Island population.

The largest number of ducks often remain on the water just off land, but recent weather conditions have forced them into local bays.

A pair of greater scaup, more commonly known as bluebills, take the cold weather in stride. – Photo by Matt Pelikan

Regardless of how harsh a winter is, Martha’s Vineyard is always the seasonal home for a lot of ducks. Our productive bays, ponds, and shoals invariably attract scoters, eiders, mergansers, buffleheads, and other “sea ducks” by the thousands, sometimes the tens of thousands.

This invasion of avian seasonals may not be all that apparent to the non-birder: The largest rafts of ducks spend much of their time feeding or just bobbing on the swells a long way offshore, and even many thousands of ducks, spread out along our lengthy shoreline, doesn’t look like much if you’re not paying attention. But the right weather conditions hitting at the right point in the season can dramatically alter the picture, concentrating ducks in highly visible areas, swelling duck numbers, and changing the mix of species that is present.

A good, vicious cold snap in late winter invariably does the trick, especially if storms and heavy snow are involved. Sound familiar?

In a dramatic but utterly predictable phenomenon, the past few weeks have seen a notable increase in the numbers of certain duck species, coinciding with an equally dramatic change in duck distribution and behavior. As tough and hardy as these birds are, freezing water effectively represents a loss of habitat for them, and in weather like we’ve been having, large numbers of wintering waterfowl have suddenly moved south, concentrated on remaining areas of open shallow water, or both.

In particular, scaup (“bluebills” to many Islanders, especially those who hunt) typically start the winter in large numbers not far north of us, on ponds both inland and coastal. Scaup also winter routinely in modest numbers on the Island’s Great Ponds. But when the ponds on the southeastern coastal plain of mainland Massachusetts, across the water in Barnstable County, or on the Vineyard itself, lock up, rafts of scaup (there are two species, but never mind) must relocate.

Favored destinations include openings of embayments and other shallow but productive sites where tidal flow or even vessel traffic keeps the water open. And so, for example, scaup flocks have recently turned up on a small unfrozen portion of the Lagoon, where they are readily visible from the municipal boat landing.

These birds are surely reserving the right to move farther south: Ducks can easily travel hundreds of miles in a day if they feel the need. But clearly scaup wintering in our region have committed, in some dim, birdy way, to a strategy of investing as little energy as possible in migrating. If they can stick out a week or two in temporary quarters, conditions will likely moderate and allow them to begin the move back toward their breeding grounds. Their boldness may translate to an early arrival, and perhaps a better chance of reproducing than birds that moved farther south.

Other species have been on the move, too, though some species are more affected by harsh winters than others. Scaup and some of the smaller sea ducks, notably buffleheads, prefer to feed in relatively shallow water, which of course is what freezes up first. Hence, we get a surge of these species. Common eiders, in contrast, don’t care much at all about the weather: Massive, famously insulated, and comfortable in deep water whether feeding or resting, they often don’t seem to react at all to a cold spell.

Overall, then, duck numbers have increased, more so with some species than with others. And ducks in general (but again, some species more than others) have gravitated to a limited number of sites, many of which, happily for a birder, are easily accessible.

Last Thursday inside the opening of the Lagoon, I found about 250 scaup (mostly in one large raft, closely packed as is typical of bluebills), two dozen common goldeneyes, roughly 30 red-breasted mergansers, 50 buffleheads, and smaller numbers of another four or five species. A single Barrow’s goldeneye, uncommon on the Vineyard, was the highlight of the mix.

Similarly, as the noon ferry unmoored in Woods Hole on Saturday, a dozen species of ducks were visible from the weather deck. Again, scaup were by far the most common: Several flocks of a couple of hundred each were stretched out along the waterfront, where, I think, they were picking mussels or other edibles off the submerged portions of seawalls and pilings. The Woods Hole channel itself was alive with long-tailed ducks, goldeneyes, and common eiders.

Waterfowl concentrations like this are short-lived, dispersing as soon as conditions moderate, and they don’t occur every winter by any means. But they offer a chance for good looks at a diverse mix of ducks — with, if you’re lucky, something unusual thrown in. For me, they’re also a reminder of how specific the seasonal needs of a migratory species can be: It may only matter for a few days or weeks, but the overlap of productive waters and fast currents offers a temporary refuge that tides these birds through a harsh season.

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Some kinds of bugs are notorious for finding their way indoors during the coldest months.

Running crab spiders run their prey down by bursting from ambush like tiny eight-legged cheetahs. – Photo by Matt Pelikan

For someone who enjoys the study of insects and spiders, deep cold and deeper snow represent mighty hard times. I’m pretty much reduced to hoping for a thaw.

But there are a few arthropods that turn up quite regularly in winter — inside houses. Some kinds of stinkbugs, leaf bugs, and ladybugs, which naturally seek sheltered enclosures in which to overwinter, are notorious for finding their way indoors and popping out during the coldest months. Cellar spiders, as their name suggests, often prefer a basement to any natural environment, and these gangly critters can be found inside in various numbers year-round.

But during much of the winter, the bug hunting inside is no better than it is outdoors. So I was pleased when a spider recently tumbled out of a ceiling fixture in which I was changing a light bulb. Long-legged, pale brown, subtly speckled, and with a body about the size of a dried kidney bean, it lowered itself just in front of my face on a strand of silk.

It’s very possible I feel differently about spiders than you do. I can’t say I totally lack the visceral fear most people seem to feel about spiders; handling anything other than a small one makes me mildly uneasy. But my main reaction to a spider is curiosity: These are remarkable animals, coming in an astonishingly wide range of forms and exhibiting life histories that vary just as dramatically. And they play a vital ecological role in regulating the populations of a huge range of prey species. So my interest was piqued.

Caught by surprise on a stepladder, with a screwdriver in one hand, I was not in a position to snag this spider when it bailed out in front of me. And when it hit the floor, it put on a remarkable burst of speed, dashing sideways to concealment under the baseboard radiator.

Over the next week or so, I saw the spider several times, sometimes clinging upside-down to the ceiling, sometimes in a corner of the ceiling and a wall, where it wove sparse, seemingly random nets of invisibly fine silk. These looked to be intended simply as a comfortable place to hang out; they were too small and disorderly to have any hope of catching an insect. Whenever I tried to get a close look at my new friend, it rappelled to the floor and disappeared.

Finally I caught it unawares as it idled on a wall. I stealthily went for my camera, turned on all the lights in the bathroom, and took a few shots. Then, very slowly, I moved my hand close to the spider, and when I gave it the gentlest of nudges, it transferred to my hand. I one-handed a few more photos, then brought the spider down to the baseboard radiator and, with a puff of breath, blew it under. That was the last I saw of it, but I bet it’s still around.

The pictures, taken in dim, artificial light, were poor, but I got to work on my favorite arthropod ID web site, BugGuide.net. Scanning representative photos of spider families, I explored groups that had members resembling my little buddy. One pronounced characteristic turned out to be especially useful: The longest legs were the second ones from the front, an unusual thing in spiders, and strong evidence that mine belonged to the family Philodromidae, or so-called “running crab spiders.”

A fairly diverse family of about 30 genera and 500 species worldwide, running crab spiders typically show the speed and habits I had observed. They run their prey down by bursting from ambush like tiny eight-legged cheetahs, reserving their silk for other applications like egg sacks, simple structures like the corner perches I observed, and lines for descending.

One very large genus of this family is named Philodromus, and it didn’t take to long to determine that my spider was a member of this group. Its relatively plump body meant that it was a she. And it turns out that Philodromus, as a genus, tends to be more or less adapted to cold. Some species have found to be capable of not just moving, but capturing prey, at temperatures slightly below freezing. But tolerating cold doesn’t mean you like it, and unsurprisingly, Philodromus is another of those bugs that tends to invite itself indoors during the winter.

So there you have it. A classic Philodromus sighting! Unfortunately, the species in this genus are all very similar, and while I can narrow the identity of mine down to a half-dozen or so, I doubt I’ll ever be able to give her a species name. But I was grateful for her visit.

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Experience a multitude of seasonal cues.

On many winter days, bicycling offers a chance to notice subtle seasonal changes. – Photo by Kristofer Rabasca

OK, it’s true that late January is an odd time to write about bicycling on the Vineyard. But there are good reasons why the topic is on my mind.

In addition to my lifelong fascination with nature, I’ve loved bicycling since before the training wheels came off. I’ve raced bikes, cross-trained on them, toured on bikes, ridden them for fun, and now I’m a year-round commuter on two wheels. And as I try to cut back my use of fossil fuels, more and more of my interaction with nature involves two-wheel transport.

From the naturalist’s perspective, biking has three main sources of appeal. The first I just mentioned: If you’re concerned about the ecological health of the planet, finding alternatives to petroleum-powered transport starts to look like an ethical duty. But the other two reasons have a lot more to do with fun.

For one thing, a bike is faster than walking but more flexible than a car. On the Vineyard, some of the most interesting places for a naturalist to visit are out of reach of a car, but large enough so the speed of a bike is a convenience. The state forest, in particular, lends itself to bike-bound naturalizing, with a network of fire lanes that are manageable even on a road bike and easily traversed by a hybrid or mountain bike. At well over 5,000 acres, the state forest is far too large to cover in a day by walking. You won’t cover all the fire lanes on a bike, either, but you can survey a lot more habitat on wheels than on your feet.

But the main advantage of a bike is that it leaves you much more connected to your surroundings than a car does. Released from your sheet-metal cage, traveling at a slower and more civilized velocity, you can see, hear, and smell the natural world from a bike. You can feel subtle changes in microclimate. How much you actually detect, of course, depends on your skill as a naturalist, and it’s a regrettable fact that the ability to read nature, like any other sophisticated ability, takes time and effort to develop. But whatever your skill level, you’ll notice more while biking than driving. I’ve been naturalizing as long as I’ve been biking: with a birder’s ears and a sharp eye for bugs, I have no problem identifying bird songs or spotting, sometimes even identifying, roadside butterflies as I ride.

Which brings me to late January, a point in the year that my naturalist self finds especially stimulating. The days are lengthening, and the rate at which they get longer is accelerating (it peaks at the spring equinox). The air is warming: We’ve passed the statistically coldest date of the winter (around Jan. 20), and while there is plenty of cold yet to come, the trend is irrevocably toward milder air (and better biking weather).

And the natural world responds to these cues — subtly at first, then not so subtly, as birds, plants, insects, and other wild neighbors start to tool up for the season of growth and reproduction. Every season, this process catches me a little bit by surprise, and each little sign of the progress of the season lifts my spirits.

In effect, my daily commute represents a repeated sampling of how the season is progressing along my route. I’ve already heard my first chickadee, titmouse, and house finch songs; soon cardinals will be tuning up; and the sonic landscape will, day by day, grow richer and more interesting. New birds will arrive. Plants will break dormancy. Insects will emerge. As the weather improves, I’ll starting taking the scenic route home sometimes, adding in a few miles of state forest bike path or back roads. A high percentage of my “firsts for the year” will be seen or heard as I spin silently along on my bike.

Honestly, year-round bike commuting is not for everyone. Some winter days can actually be comfortable for a short ride with appropriate clothing on, but many days are not: bicycling in 15 degrees and a strong headwind is unpleasant, period. And riding in rain or snow requires either fortitude that goes beyond even my own, or else the option of driving to work or working from home.

But for anybody who enjoys observing nature and can handle a few miles on a bike, I’d strongly suggest looking for chances to combine the two. And think about starting on a nice late winter day, as the world is waking up. You can bring binoculars, field guides, and a camera in a bag or backpack. You can cover a lot of ground. And you can feel sure that you’re experiencing a multitude of seasonal cues being missed by the folks in the metal boxes.

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How does a bird like an oriole, essentially a tropical species that disperses northward to breed during the summer, handle the deep freeze?

Winter, generally speaking, is a season I could live without. But I’ve always had a fascination with the ways wildlife responds to adversity, and the early January cold snap represented a fine opportunity to contemplate this subject. After several days of merely cold weather, the mercury bottomed out on the night of Wednesday, Jan. 7. Our porch thermometer in Oak Bluffs dipped to slightly below zero before sunrise Thursday morning; reports from elsewhere on the Island suggested that virtually the entire Vineyard hit zero or below.

My first thoughts were for a particular bird implausibly lingering at this latitude: a first-year male Baltimore oriole that has been frequenting feeders in West Tisbury for several weeks now. A familiar sight and sound on the Vineyard in summer, when they nest in deciduous trees across the Island, Baltimore orioles are ill equipped for winter. With long, pointed beaks, they’re optimized for eating insects, and struggle to eat the seeds that represent the bulk of the available food supply in winter.

Accordingly, orioles are strongly migratory. The heart of their winter range is Central America, though the species is regular in Florida and the West Indies in winter. But oddly, the Baltimore oriole is a bird that has always been prone to lingering in the North in small numbers, and in recent years, it seems like this imprudent behavior is growing more common. Perhaps not quite annual on the Vineyard in early winter, Baltimore orioles are approaching that degree of regularity, and the sight of one of these orange avian gems in early January is no longer much of a surprise.

The West Tisbury bird (it seems that only one individual was involved) was reported from several feeding stations, eating suet and doing its best with seeds. The last report I heard came from early on the morning of Jan. 8, so it survived the night of the deepest cold. Whether it lived beyond that is not clear, and even if it did, it may have relocated. So we may never know its fate.

How does a bird like an oriole, essentially a tropical species that disperses northward to breed during the summer, handle the deep freeze? The availability of a reliable food source, preferably with high-energy options like suet, is surely a critical element. Given enough calories to keep its internal furnace running, a bird can withstand surprisingly low temperatures, and the kindhearted birders providing food for the West Tisbury oriole were surely keeping it alive.

The real sticking point for such a bird is nighttime, when the temperatures dip to their lowest and when

How does a bird like an oriole, essentially a tropical species that disperses northward to breed during the summer, handle the deep freeze?
-Photo by David Brezinski, U.S. Fish and Wildlife Service

protracted darkness makes it difficult or impossible to forage for ten hours or so at a time. About the only thing an oriole or similar species can do to survive the night is hunker down in a sheltered spot, fluffing out its feathers for maximum insulation and probably settling down on its perch so that its bare legs and feet, vulnerable to frostbite, are covered by belly feathers. At first light, feeding as heavily as possible is critical, and if conditions allow, soaking up whatever warmth can be gleaned from the winter sun is a help.

So much for the how; the other question is why? Migrants that linger into winter are often injured or sick birds, not fit for undertaking the journey south. But many, perhaps most, of the birds like the West Tisbury oriole appear perfectly healthy, and it seems probable that they simply lack the instinctive impulses that should trigger migration. The outcome of failing to migrate is usually not a happy one for the individual bird. But from the larger perspective of an entire species, defective instincts are probably a good thing: that’s the sort of variation that allows a species to adapt to climate change or the loss of traditional wintering areas, with the occasional misdirected bird surviving to discover new sites or strategies for surviving the cold months. Defective migrants, in other words, may be part of the evolutionary strategy of birds.

Interestingly, some species are more prone to linger than others. The orchard oriole, for example, is a close relative of the more common Baltimore oriole, but unlike the latter species it is almost unheard of in the Northeast in early winter (though it often turns up on the West Coast as a vagrant). Likewise among the warblers, some species, such as black-throated blue warbler, seem to linger with some regularity, while others — say, bay-breasted — seem to bail out for warmer climes with complete reliability. To some extent, migratory patterns may explain the differences, with the species that winter farthest to the south least prone to linger. But in the absence of actual records, it would be hard to predict reliably which species would be most likely at our latitude in winter.

In any event, I’m rooting for the West Tisbury oriole. He’s got high-quality food sources and even a few heated birdbaths available, if he can find them. And he’s demonstrated great tenacity and resourcefulness — even if he missed the memo on migration.

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Is it a spear? Some sort of ancient weaponry? And where might its owner be? – Photo by Danielle Zerbonne

The great outdoors can produce baffling mysteries. MVTimes Wild Side columnist Matt Pelikan tries his best to solve them. Got a question for the Wild Side? Send it to onisland@mvtimes.com.

Dear Matt,

Found this on the beach behind my office. When I brought it in and showed it around, I was surprised how many people had no guesses as to what it is. An interesting find! My question is, are horseshoe crabs in trouble or what? I know their mating is monitored and also that they are chopped up for bait by the truckload at a Vineyard Haven business. What’s the deal?

Hi,

As menacing as this object looks, it’s a harmless piece of the anatomy of an equally harmless arthropod, the horseshoe crab. Not actually crabs, these odd-looking animals are more closely related to terrestrial spiders. There are four species worldwide; ours, the Atlantic horseshoe crab, occurs on the East Coast and in the Gulf of Mexico. Named for its overall body shape, the horseshoe crab is one of the most ancient creatures still extant, with a lineage dating back about 450 million years.

The aftermost body segment of these primitive sea creatures, the spike-like “tail,” or telson, guides, stabilizes, and helps right a horseshoe crab as it skims over the sea floor (often upside down!). The telson may also contain sensory organs to help the crab keep tabs on surrounding conditions. But the spike plays no role at all in self-defense, and indeed, except for its robust shell and a fringe of small, movable spines along its back edges, a horseshoe crab is defenseless.

Or you might say that being prolific is the defense strategy of the species. Horseshoe crab eggs are eaten in large quantities by a wide range of other animals, and young crabs are likewise tempting prey. But horseshoe crabs are highly prolific — they simply lay enough eggs, about 80,000 per female according to most sources — so that some are sure to escape being eaten. And by concentrating their egg-laying into narrow time windows, horseshoe crabs overwhelm the ability of predators to consume eggs. Mature crabs come ashore to spawn primarily around full and new moons (associated with particular high tides) in spring, mating and laying eggs near the wrack line.

Though horseshoe crabs have survived ice ages, mass extinctions, and the evolution of advanced predators, overharvest by humans (spawning crabs can simply be picked up off the beach) has threatened their survival in some regions. Horseshoe crab blood is a valuable resource for the biomedical industry, and for years crabs were harvested and drained of their blood. Current methods are less lethal — the crabs are generally caught, partially bled while still alive, and released; survival is said to be high, but the process must surely stress the crabs. On the Vineyard, horseshoe crabs are harvested mainly to be cut into bait for the conch pot-fishery, said to be the Island’s most valuable fishery.

Since other animals feed heavily on crabs and crab eggs, the decline in horseshoe crab numbers has echoed through the marine ecosystem. In particular, migrant shorebirds traveling along the East Coast of North America rely on crab eggs for fuel, timing and routing their migration to exploit the spawning cycle of the crabs (most notably along the shores of Delaware Bay). Without enough crab eggs to feed on, these birds may be unable to complete their northward migration, or, if they can reach their Arctic breeding grounds, they may have insufficient energy reserves for successful reproduction.

Horseshoe crab conservation measures, such as prohibiting harvest at the times of peak spawning or prohibiting the taking of females, have been put in place in several key states and may reverse the decline of these interesting and ancient animals, in turn helping to conserve shorebird populations. But horseshoe crabs mature slowly, not spawning until they’re nine or 10 years old, according to Island naturalist Suzy Bowman. So a meaningful rebound of the crab population may take some time.

Since 2008, numbers of spawning horseshoe crabs have been monitored at a couple of key Vineyard spawning sites as part of a larger effort coordinated by the state’s Division of Marine Fisheries. Ms. Bowman, who helped get the Vineyard effort up and running, says that the count of spawning crabs along the Lake Tashmoo and Sengekontacket shorelines may still be declining (though the data are not conclusive). While acknowledging the economic importance of harvesting (or bleeding) horseshoe crabs, the Wild Side perspective is that these ancient arthropods play critical roles in the inshore marine ecosystem, and management to ensure their recovery and survival is essential.

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Photo by Sarah Mayhew

The start of the new year coincides with the closest we ever come to a true pause in the movement of birds through our region. Fall migration has ended, though a few disoriented individuals or stragglers may still be wandering. And the first inkling of spring migration, in the form of incoming red-winged blackbirds or northbound ducks, is still a month or so in the future.

But there is no such thing as true stasis in the bird world, and indeed, the first days of January are as good a time as any to hope for the arrival of our most interesting avian visitors. A good example would be the dovekie, a tiny but incredibly hardy seabird that is rarely seen on the Vineyard, but has lately put in an appearance.

Dovekies are members of the auk family (the European name for the same species is “little auk”). Like other auks, the dovekie is strongly associated with oceanic habitats: sea cliffs in Greenland, Iceland, northernmost Europe, and arctic islands during the breeding season, and cold Atlantic waters, generally north (sometimes far north) of the 42nd parallel in winter. [Martha’s Vineyard Airport is at 41.39 degrees N.]

Abundant birds, dovekies are estimated to number in the millions. But their maritime lifestyle keeps them in remote regions and, usually, far from land except when they’re nesting; it’s easy for a Vineyard birder to go for years without seeing one. But photos have recently been taken of dovekies at Menemsha, Lambert’s Cove, and Vineyard Haven harbor, and a dead one was found on land at Cedar Tree Neck. A spate of other sightings in southern New England suggest that this may be a good year for finding this odd bird.

Like many other kinds of seabirds, dovekies are subject to being driven far off course by storms. When coastal storms coincide with a robust movement of dovekies, hundreds of these birds may be blown far inland, where many or most perish from exhaustion, starvation, and an unfortunate inability to get airborne once they’ve landed on a hard, flat surface.

But storms don’t account for all the wanderings of this species. Dovekies have turned up many hundred of miles south of their normal wintering range, often with no indication that bad weather accounted for their occurrence. And sometimes mass movements of these birds have been observed from coastal vantage points under fine conditions. However they gain it, dovekies obviously have a sophisticated understanding of geography and are capable of prodigious movements in search of resources.

Dovekie-Menemsha -Sarah Mayhew-2.jpgBlack-and-white, barely eight inches long and a foot across the spread wings, and weighing in at about six ounces, a dovekie is about the size and build of a mourning dove missing its long tail feathers. Like all the auks, a stocky family, dovekies are marginal aerialists, able to keep aloft only through comically frantic wing-beats. Nesting on sea cliffs, they take off by plunging toward the water to build air speed, and taking off from water requires a long take-off run.

But in the water, it’s another story. Dovekies, like all the auks, spread their wings to “fly” underwater and a dovekie can dive to more than 100 feet and stay submerged for several minutes if it feels the need. In effect, they’ve followed the same evolutionary route of the penguins, only not quite as far: auks retain the ability to fly, but their true home is in saltwater. It’s hard to believe, but millions of these tiny birds survive winter on the frigid waters of the North Atlantic each year, often without ever setting sight on land.

One secret to the success of the dovekie is probably the dietary preference of this species. They are known to feed primarily on plankton, especially the tiny but not truly microscopic arthropods that make up the lower rungs of the marine food chain. Focused on a plentiful and widespread food supply, dovekies may have an advantage over their larger relatives, most of which focus on fish — a less evenly distributed and less dependable food source.

Oddly, the birds recently photographed on the Vineyard were feeding on Atlantic silversides, schooling fish that range up to about five inches in length. This food choice is hardly unprecedented in dovekies, which are opportunistic and frequently include small fish in their diet. But the presence of these birds inshore, and in areas rich in bait fish, make one wonder whether something has happened to the offshore plankton supplies that would normally be sustaining these birds.

How long the species will linger here is anyone’s guess and hopefully at least one will stay for this weekend’s Christmas Bird Count! But Island birders are happy to have an opportunity, however brief, to search for this hardy, mysterious bird.