Speak for the Trees

Yellow-legged Hornet photographed again near the Soignes in September

A Yellow-legged Hornet (Vespa velutina nigrithorax) was photographed on Henri Schoofslaan in Auderghem on September 8, a few streets from the edge of the Forêt de Soignes. It's the invasive Asian hornet known for preying on honeybees, and iNaturalist records show it turning up repeatedly across the wider Brussels region this year: well over a hundred sightings logged in the past twelve months alone, spanning communes from Auderghem, Ixelles and Watermael-Boitsfort to Tervuren, Wemmel and Leuven. That pattern of records doesn't establish population size or trend — sightings track observer effort as much as anything — but it does show the species is being found widely and repeatedly around the forest, not just this once. Telling it from the native European Hornet takes one look at the color. The European Hornet is a big yellow wasp with black bars and a reddish-brown head and thorax. The Yellow-legged Hornet is the reverse: velvet black or dark brown, each abdominal segment edged with a thin yellow line, a single broad orange band toward the tail, an orange face, and legs that end in bright yellow as if dipped in paint. It usually runs a little smaller. The yellow feet are the mark most people catch first. September is when its colonies are as large as they will get. A nest at this point holds a few thousand individuals, and the workers are provisioning larvae at full tilt. This is the month for the behavior beekeepers dread: workers hang in the air in front of a hive entrance, pick off single bees returning heavy with pollen, then cut away head, wings and legs and carry the thorax home. Honeybees are not the whole diet, though. Nests studied in southwest France took honeybees for about 38 percent of their prey, flies for about 30 percent and other social wasps for about 20 percent, with more than 150 prey species in all. Colonies near forest leaned harder on native wasps; colonies in town leaned on honeybees. A single nest can take roughly eleven kilograms of insects in a season, which is why the concern extends to native pollinators and not just to hives. The nest itself is usually invisible right now. A queen starts small in spring, low in a shrub or under a roof edge, and by summer the colony shifts to a large paper nest high in a tree canopy. In beech and oak stands like the Soignes those only show once the leaves drop in October and November, by which point the colony is already producing next year's queens. Workers and the old queen die with the cold. Only the mated young queens overwinter, each one capable of founding a new nest in spring. Brussels handles this through Bruxelles Environnement, which trains a referent in each commune to take sighting and nest reports. A hornet hovering at a hive, or a large grey nest appearing in a bare canopy this fall, is what to report.

Elegant Terns arrive on Tillamook Bay, riding the anchovy run north

Elegant Terns are on Tillamook Bay this week. Twenty-nine were counted on the bay on September 6, and observers have kept reporting them in the days since. For a bird that nests almost entirely on one small island in the Gulf of California, the northern Oregon coast is a long way from home, and September is exactly when the species gets here. The Elegant Tern (Thalasseus elegans) is the smallest of the three crested, orange-billed terns that show up on this coast, and the easiest way to pick one out is to stand it next to the others. Caspian Terns, the big ones that have been rasping over the bay all summer, carry a heavy blood-orange bill and show mostly dark undersides to the outer wing. Royal Terns sit in between in size and bill weight. An Elegant Tern is slim and long-winged, with a thin yellow-orange bill that droops a little at the tip, a shaggy black crest that by fall has pulled back to leave the forehead white, a deeply forked tail, and pale underwings tipped in black. On a tideflat the Elegants tend to stand in their own tight knot a short distance from the Caspians rather than mixing in. In the air they flutter on narrow wings and drop straight into the water after small fish. Those fish explain the whole story. Elegant Terns feed heavily on northern anchovy, and once the breeding season ends on Isla Rasa the birds scatter along the coast in both directions, following the schools. Each autumn a pulse of anchovy moves north up the California Current, and Brown Pelicans, Heermann's Gulls and Elegant Terns ride along behind it. How far north the terns push varies from year to year with where the fish are. Their movement tracks anchovy availability, which itself shifts with ocean conditions off Baja California. Brown Pelicans and Heermann's Gulls are on the bay this same week, the same company the terns keep down south. Elegant Terns remain an uncommon enough visitor here that the reports were flagged when they came in. The place to look is the sandbars and tideflats at low tide, where the flock loafs between feeding runs, and the channels and nearshore surf where single birds hover and plunge. A slender, drooping bill and a nearly white underwing are the two marks that settle it.

A single American Golden-Plover refuels on farm ground west of Fowlerville

A single American Golden-Plover (Pluvialis dominica) has been working the farm ground along West Sherwood Road west of Fowlerville for the past several days, seen again on September 7. It is a long way from any shoreline, and that is the point. This is a shorebird that prefers dirt to water: plowed fields, sod, short pasture, anywhere the vegetation is low enough that a bird can see what is moving on the ground in front of it. Watch it for a minute and the method is plain. It runs a few steps, stops dead, scans, then darts forward to pick something off the soil, much the way a robin hunts a lawn. It is finding prey by eye, not by probing, which is why it wants bare or close-cropped ground rather than the mudflats other shorebirds crowd onto. In a September field that means beetles, grasshoppers, ants, flies, spiders and earthworms turned up by tillage or exposed on short turf. By this date the bird has mostly shed its summer look. The black face and belly and the gold-spangled back that give the species its name are gone or going; adults are patchy and buff-gray, and a juvenile wears crisp, evenly scaled plumage with a fine gold speckle across the back. In that drab state the bird to rule out is the Black-bellied Plover, which also stops in fields on migration. The golden-plover is smaller and slimmer, with a noticeably finer bill and a smaller head, and its folded wingtips extend well past the tail. If it lifts, the difference is settled at once: Black-bellied shows a black patch in each wingpit in every plumage, golden-plover's underwing is plain gray, and its rump and tail are dark like its back rather than pale. This bird is partway through one of the longest journeys any shorebird makes. It nested this summer on Arctic tundra somewhere between Baffin Island and the Bering Sea. It will winter on the pampas of Argentina, Uruguay and southern Brazil. The route is a loop rather than an out-and-back: in fall most of the population stages along the Atlantic coast of Canada and New England and then flies nonstop over the western Atlantic to the north coast of South America, a single overwater leg of roughly 2,400 to 3,100 miles with nowhere to land, rest or feed. In spring they come back up through the middle of the continent, through the Great Plains and Mississippi Valley, feeding in open fields much like this one. The full circuit runs on the order of 20,000 miles a year. A field in Livingston County is an inland refueling stop on the southbound leg, after the tundra and before the coast. Adults leave the Arctic first, in July and August, and juveniles follow from late August into October, so the timing here fits either a late adult still heading south overland or a first-year bird on its first passage, fattening on Michigan insects before a flight that will not touch ground again until Venezuela or the Guianas.

A Connecticut Warbler pauses on the ground before its Atlantic crossing

A Connecticut Warbler (Oporornis agilis) turned up on September 11 on a restricted-access property along Posquiello Creekside Road, a single bird working the ground cover. It is one of the least-seen warblers in the East. Most birders who have one on their list found it this way, on a fall stopover in the Northeast, and never on its breeding grounds in the tamarack and spruce bogs and jack pine stands of the boreal forest. It is a plump, short-tailed warbler with a gray hood, an olive back and a yellow belly. The mark that catches the eye first is the eye-ring: complete, white and bold. The legs are long and pink, the bill is heavy and spike-like, and the feathers under the tail run nearly to its tip. Mourning Warbler is the lookalike. It is slimmer, its eye-ring is broken or missing, and a male in spring carries black on the breast where the Connecticut is plain gray. Nashville Warbler has a similar eye-ring but a yellow throat, is much smaller, and feeds up in the trees. The surest tell is how it moves. A Connecticut Warbler walks. It paces slowly along the ground or a low branch, bobbing its short tail, and flips dead leaves to get at the insects underneath, the way an Ovenbird does. Nearly every other warbler hops. On stopover it keeps to the bottom of the understory: weedy field edges against woods, thickets, tangles of goldenrod and jewelweed. Whoever is looking for one is looking at the ground, not the canopy, and usually waiting a long time. The bird's migration runs in a loop. In spring it comes north through the middle of the continent. In fall it swings east to southern New England and the Atlantic coast, and from there it flies out over open ocean. In 2017, researchers fitted geolocators to birds breeding in Manitoba and later recovered four of them. The tracks they read showed roughly 48 hours nonstop over the Atlantic, some 1,700 to 2,400 kilometers, to Cuba or Hispaniola. The birds then spent about a week on the ground there. From there they crossed another 800 kilometers of water to Venezuela and continued on to wintering grounds in the Amazon basin. The bulk of the species passes through the Northeast in the second half of September. A bird on the Hudson on the 11th is on the early side of that window, feeding in the leaf litter before the long overwater leg.

Henslow's Sparrows stage at Peck Farm on the way south

Two Henslow's Sparrows were reported in the tallgrass prairie at Peck Farm Park in Geneva on September 7, part of a handful of early-September checklists from the Geneva Park District's 385-acre park, in an area generally described as the western edge of the morainal country. Henslow's Sparrow (Centronyx henslowii) is a bird more people have read about than seen. It spends nearly all its time on the ground inside dense grass, walking and hopping rather than flying. When flushed it flies low for a few yards and drops back into cover. Its song is a dry two-syllable "tsi-lick," delivered from a low grass stem, often called the weakest song of any North American songbird. Anyone trying to pick one out from the other small sparrows in the same grass should look at the head. Henslow's is stocky and short-tailed with a flat-looking, oversized head washed olive-green on the face and nape, and the breast is streaked dark. Grasshopper Sparrow, its closest lookalike, is paler and buffier with a clean unstreaked breast. Savannah Sparrow shows crisp streaking on white underparts and a yellow patch in front of the eye that neither of the others has. What the birds at Peck Farm are doing is fueling up. Henslow's Sparrow breeds in Illinois. It needs large tracts of grass left unmowed and unburned long enough to build a thick mat of dead stems and litter, and the state's breeders have mostly left by late August. Birds still in northern Illinois in September are almost certainly migrants passing through at night toward wintering grounds on the southeastern coastal plain. In September they are still eating mostly insects, crickets and short-horned grasshoppers above all, plus beetles and caterpillars. The shift to a seed diet of wiregrass, sedge, ragweed and smartweed comes in winter, farther south. The litter layer is the whole story for this bird. It nests low in the grass under standing dead stems from prior years, and it will not use a field that was burned or hayed the same season. That puts it in tension with prairie management, because tallgrass prairie needs fire to keep shrubs and trees out. Studies of burned grasslands show Henslow's numbers dip the first summer after a burn, peak in the second and third years as the thatch rebuilds, and fall off again by the fourth as the stand gets too rank. The answer managers have settled on is to burn in rotation, a third of the ground at a time, so some patch is always in the two-to-three-year sweet spot. The Geneva Park District manages roughly 300 acres of prairie across its properties and burns about 100 acres every 18 months, which is that rotation in practice. Rangewide, the species lost enormous ground through the twentieth century as prairie and hayfield went under the plow, and estimates from Partners in Flight put its global population at roughly 410,000 birds, though figures vary by source. Since the early 1990s, idle grassland set aside under the Conservation Reserve Program has driven local increases across parts of the Midwest. Some Bird Conservation Network surveys in the Chicago region have suggested an increase over the past fifteen years, though the trend is not consistent across all survey sites and sizeable populations remain confined to large grasslands. The prairie at Peck Farm is far smaller than that. It is a place a migrant can drop into for a few days on the way south, and that depends on the grass being there, thick and unburned that season, when the bird arrives.

Black Storks ride the ridges toward Tarifa in peak passage week

Black Storks are passing over the Sierra de Alpujata. On September 3, watchers at the Mirador de las Águilas above Mijas logged them on half a dozen checklists, never more than two at a time, riding thermals off the ridge on their way southwest. That is right on schedule. September is the peak month for the species at the Strait of Gibraltar, and this lookout, which exists to count soaring birds on the autumn passage, sits roughly a hundred kilometers up the coast from the crossing at Tarifa. Overhead, a Black Stork (Ciconia nigra) is easy to mistake for its common cousin until the light hits it. Both are the same size, about a meter tall with a wingspan near a meter and a half, and both fly with neck and legs stretched straight out, which is what separates any stork from a heron. The White Stork is white with black flight feathers. The Black Stork is the reverse: black head, neck, back and wings, with a green and purple gloss in good sun, and white confined to the belly and undertail, so the bird reads as dark with a pale patch behind the legs. Where White Storks cross in flocks of dozens or hundreds, Black Storks come singly, in pairs, or in small loose groups, which is why two at a time is a typical count here. The habits are as different as the plumage. White Storks stride through open pasture and follow tractors; Black Storks are shy, wading slowly through shallow rivers and marshes, usually alone, hunting by eye. The bird walks head-down through the water or stands with wings outstretched, then lunges with the long bill. Fish make up most of the diet in the breeding season, with frogs, eels, salamanders, small reptiles and the occasional small mammal filling in. Iberian pairs are unusual among Black Storks in that many nest on cliffs, boulders and overhanging ledges in mountain country rather than in big forest trees, and they are wary enough that finding and monitoring those nests is hard work. The birds crossing the Málaga sierras now have a reason to hug the ridges. A stork is a soarer, not a flapper. It climbs on a column of warm air rising off a sun-heated slope, glides to the next, and climbs again. Cold sea makes no thermals, so the last thing a three-kilogram bird wants is to leave land early. The coastal ranges, Alpujata, Sierra Bermeja, then the hills above Tarifa, work as stepping stones that deliver it to the narrowest point of the Strait with height to spare for the fourteen-kilometer jump. Those that cross keep going to the West Sahel, wintering on wetlands in Mali and Nigeria. Not every Iberian Black Stork makes the trip anymore. Since at least the early 2000s a growing number have stayed to winter in Spain and Portugal, most of them on rice fields, reservoirs and ponds. Spain lists the species as Vulnerable in its national catalogue of threatened species, and the pressures named are the ones that hit its feeding water: altered river flows, drought, over-extraction and pollution, all a long way from a dry ridge like this one. Counters at the Mirador de las Águilas have tallied nearly 900 Black Storks since 2008, a small share of the soaring traffic on this flyway but a steady one. A dark stork over the ridge in the first weeks of September is exactly what the lookout was built to catch.

A Green Snaketail turns up over the mining-shaped Bolina valley

A Green Snaketail (*Ophiogomphus cecilia*) was recorded twice on August 27 in the Bolina valley in Katowice, the two sightings a few hundred metres apart on the stretch of stream and old mine ponds between Giszowiec and Janów-Nikiszowiec. It is a dragonfly of sandy lowland rivers, and the ground it was seen over is about as far from that as Upper Silesia gets. The adult is hard to mistake once seen well. It is a large dragonfly, 50 to 60 millimetres long, with an apple-green face, green eyes and a green thorax marked with thin black lines. The abdomen is black with a broken run of yellow triangles down the top and widens slightly toward the tip into a modest club. The eyes do not meet on top of the head; a small ridge sits between them, which is the mark of the clubtail family. Freshly emerged animals show no green at all and take on the colour only as they mature. Males hold perches on sunlit stones, sandbanks and bare branches over shallow, fast water and patrol short beats low over the surface. They avoid shaded banks. The larva is where the species' needs are set. It is a burrower, built with a flat, shovel-like lower lip and digging front legs, and it spends two to four years buried in the sand or fine gravel of a flowing river bed, taking whatever small invertebrates pass. It digs in almost the moment it touches bottom, at any current speed. That is why the species drops out of rivers that are straightened, dredged, lined with concrete or smothered in silt: whatever the water chemistry, there is nothing left to burrow into. The EU protects it under the Habitats Directive, and the loss of sandy river beds is the main threat named in its accounts. The Bolina is a regulated and polluted stream for most of its length. The ponds strung along it, Staw Bolina among them, formed out of mining, and the greatest variety of life on the stream is found at its headwaters and around those ponds, which is where both records sit. Whether a river dragonfly is breeding anywhere in that system is a question two sightings cannot answer. Adults of this species regularly wander several kilometres from the river they emerged in, into sunny clearings and along heated paths, before returning to water to breed. August 27 sits inside the normal June-to-September flight season, a few weeks past the late-July to mid-August peak. So a dragonfly whose whole early life depends on clean, loose river sand was flying over a valley that mining shaped. Anyone walking the paths around the Bolina ponds on a sunny September afternoon can still look for a green-fronted dragonfly the length of a finger, sitting flat on bare ground or a stone, and know what it takes to make one.

Severe drought locks in over Cumberland County, and the small streams show it first

Severe drought arrived in Cumberland County in the middle of August and has not let go. On the August 4 drought map, none of the county was in severe drought. One week later, just under a third of it was, and that share has held flat at 31.59 percent for four straight weekly updates through September 7. Moderate drought or worse now covers 68.91 percent of the county, up again this week, and the whole county is at least abnormally dry. No part of it has reached extreme drought. The rain is not coming to fix it. The Portland Jetport station, four kilometers from this stretch of coast, has recorded a tenth of an inch so far in September against a 1991-2020 normal of 0.62 inches for the same days. Overnight lows there are running a couple of degrees above normal. Last summer the county came through its third-driest June-to-August on record, so this is dry ground going dry again. The place that shows it first is the small water. The Stroudwater, the Nonesuch, the Spurwink and the little Presumpscot tributaries that feed Scarborough Marsh are low-gradient, shallow streams with thin groundwater reserves. When base flow drops, they stop running and start pooling. The riffles that normally stir air into the water go dry or shrink to a trickle. The pools left behind warm faster in the afternoon sun, and warm water holds less oxygen. Brook trout, a coldwater fish recorded in South Portland this spring, run into trouble near 21 degrees Celsius and avoid water below about 4 milligrams per liter of oxygen, a number a stagnant September pool can approach. Early September adds a second load on top of the first. Leaves are beginning to drop into the channels. In a stream that is flowing, that litter gets torn apart and carried downstream by caddisflies, stoneflies and mayfly larvae, the shredders that do most of the work in a forested headwater. In a stream that has stopped moving, breakdown falls mostly to bacteria and fungi. The leaves rot in place and pull oxygen out of the same pools the heat is already squeezing. The bedrock underneath most of this lowland is old metavolcanic and metasedimentary rock with almost no limestone, so the streams have little chemical capacity to buffer anything that concentrates as the water shrinks. The trees are the other place to look. True fall color comes on gradually, at about the same time each year for a given species, and moves through the whole canopy. Drought damage looks different. It shows up weeks early, patchy, one branch or one side of the tree first, with scorched brown leaf margins and leaves dropping before they finish turning. On red maple and red oak that is browning from the leaf tips inward. On white pine it is rust-colored branch tips where needles have died. A maple that goes brown and drops in early September has not had an early autumn. It has sealed off leaves it can no longer afford to keep, and the nutrients in those leaves are lost rather than drawn back into the wood. What breaks the pattern is rain, enough of it to reconnect the pools and put the riffles back to work before the water cools on its own schedule. Until then the streams of this lowland are running a deficit that started in August and is compounding into September.

Two Hudsonian Godwits refuel on the East Pond's exposed mud

Two Hudsonian Godwits (Limosa haemastica) have been working the mud at the north end of the East Pond at Jamaica Bay Wildlife Refuge, reported there repeatedly through September 7. They are plain gray-brown birds at this season, nothing like the chestnut of the field-guide breeding shots, and from the shoreline they read as a tall, long-necked shorebird with a very long, slightly upturned bill that is pink at the base. Size is the quickest handle: bigger than the Willets around them, smaller and grayer than a Marbled Godwit. If one flushes, the identification settles itself. A Hudsonian flashes black underwings, a black tail and a white rump; a Marbled Godwit flashes solid cinnamon, and a Willet shows a bold black-and-white stripe across the whole wing. The reason this pair is interesting has to do with where the rest of the species is right now. Hudsonian Godwits breed on the edge of the boreal zone, with a large population centered on the southern shore of Hudson Bay. In late summer they gather on James Bay to fatten, then most of them leave on a nonstop flight over the Atlantic toward South America, wintering on tidal mudflats in Argentina and Chile. The migration runs as an ellipse: north through the middle of the continent in spring, south over open ocean in fall. The Atlantic Coast sits off to the side of that southbound line, and the species turns up here mainly when northeasterly winds push birds inshore. Whatever brought these two down, a stop at Jamaica Bay is a chance to refuel before a flight that, for most of their kind, is measured in thousands of miles without landing. What they are doing on the mud is feeding by touch. The bill looks stiff, but the tip flexes, and the bird drives it into soft sediment, feels for something moving, clamps down, then steps forward and probes again, dowitcher-fashion, sometimes with the head under water. The catch is worms, amphipods, small crabs, snails and insect larvae living in the top few inches of mud. The East Pond is not tidal flat. It is an impoundment, and the National Park Service drains it into the bay each year from July into September specifically to expose mud for southbound shorebirds and to give them somewhere to feed and rest while the tide covers the flats out in the bay. September is the tail end of that drawdown window, which is why the north end of the pond is one of the most watched pieces of mud in New York City right now. Anyone who gets there in the next week or two has a fair chance of picking out the two gray godwits among the yellowlegs and dowitchers, and of seeing a bird that is normally far offshore at this time of year, standing in Queens.