Speak for the Trees

Sonoran Desert Tortoises are out across the Tucson basin this monsoon

Sonoran Desert Tortoises (Gopherus morafkai) have been out on the ground across the Tucson basin from mid-August into the second week of September, most of them in the Avra Valley west of the city and a smaller set on the rocky slopes below the Catalinas. This is the one stretch of the year when the odds of meeting one on a trail are good. The animal spends most of its life underground or under rock, and it comes out mainly in daylight during the monsoon, when the rain has greened up the forage and filled the shallow pools it drinks from. It is a domed, high-backed tortoise the color of the caliche it digs into, with a shell somewhat narrower and more pear-shaped than the Mojave desert tortoise's. The two species are split by the Colorado River and do not overlap here, so any wild tortoise on this side of the river is the Sonoran one. It favors steep, rocky ground and the bajadas below it, not open valley floor, and it shelters in burrows it digs itself, in caliche caves, and in rock crevices. The tortoise drinks from puddles a finger deep by putting its nostrils to the surface and pulsing its throat to pull the water in. It also scrapes basins in the soil to catch rain and remembers where they are, walking directly to them when a storm passes. What it takes in goes into a bladder that can hold water for extended periods and release it back into the bloodstream as the body needs it. When a rain finally comes after a long dry spell, a tortoise drinks heavily, voids the concentrated urine it has been carrying, and stores fresh water in its place. In a hard drought an adult can go a long time without drinking. It eats plants only, leaning on annual wildflowers first and then grasses and cactus, with prickly pear fruit taken whenever it is ripe. September is also hatching season. Eggs laid in early summer, buried in the floor of burrows, hatch in September and October, though some clutches hold over and hatch in spring. A hatchling is about the size of a silver dollar and soft-shelled for years. Only a small fraction reach adulthood. Those that do mature between 13 and 20 years old and can live 50 to 80 years, which means a tortoise crossing a trail this week may have been crossing the same slope since before the surrounding subdivisions were built. Breeding peaks in August and September as well, so two adults seen together right now are likely a courting pair. iNaturalist flags the species as threatened, but the U.S. Fish and Wildlife Service reviewed it and found in 2022 that federal listing was not warranted, and it does not appear on the current federal list for this area. The pressures on it are the same either way. Buffelgrass, an introduced African grass now widespread around Tucson, burns hot enough to kill saguaros and palo verdes on slopes that never evolved with fire. The tortoise needs an unburned desertscrub slope with rock to hide in and annuals to eat after rain. Anyone who finds one should leave it where it is. A tortoise picked up or frightened may void its bladder, and in a dry year that is the water it was counting on to get through to the next storm.

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.

Yellow-legged Hornet spotted at Waldshut, a river-crossing from Zürich

A Yellow-legged Hornet (*Vespa velutina*) was photographed near Waldshut, on the German bank of the Rhine, in the last week of August. This is the introduced Asian hornet that Swiss cantons have been asking the public to report, and Waldshut is a short flight across the river from the Unterland woods around Bülach, Eglisau and Kloten. The native European Hornet (Vespa crabro) is the thing it gets confused with, and size does not separate them. Colour does. The Yellow-legged Hornet is a dark insect. Its thorax is velvety black. Its abdomen is mostly black, with a single broad orange band on the fourth segment and a thin orange line nearer the waist. Its legs are dark down to the middle and then bright yellow to the tips. The European Hornet, by contrast, is a warm-coloured insect. Its thorax is reddish-brown. Its abdomen is largely yellow, with black markings on the front segments. Its legs are brown all the way down. The leg tips are the quickest check. Yellow feet on a dark hornet mean the Asian species. The colony is an annual structure. A mated queen wakes in March and builds a small paper nest in a sheltered spot, often on or in a building; the primary nest the City of Zürich removed in Witikon last year was in a shutter box. Once the first workers emerge in June the colony usually moves to a second, much larger nest high in a tree, often above ten metres, which can reach 60 centimetres across and hold around 2,000 workers at once. Mid-September is when these colonies are at their largest and are producing males and next year's queens. The big nests are almost impossible to see against summer foliage. Most of them are only found after the leaves drop in October and November, and by then the new queens have usually already flown. Those queens spend the winter alone in soil, in rotting logs and stumps, or under loose bark, exactly the material a broadleaf forest floor supplies. Everything else in the nest dies with the frost. The hornet earns its reputation at beehives. Workers hover at the hive entrance and snatch foragers coming home with pollen or nectar, drop them to the ground and paralyse them. Bees under this pressure stop leaving the hive, honey yields fall, and winter losses rise. It is not only a bee predator, though. A study of 16 nests in southwest France found honeybees made up about 38 percent of prey, flies about 30 percent and social wasps about 20 percent, with 159 prey species in all; colonies in forest took more wasps and colonies in towns took more honeybees. Bumblebees and solitary bees were a very small share. A single colony is estimated to take roughly 11 kilograms of insects over a season. The regional picture comes from the cantonal authorities rather than from this one sighting, and the figures below reflect how much reporting effort has gone into finding and logging nests, not necessarily how the population itself is changing. Canton Zürich received about 100 reports through the national platform in 2025. The City of Zürich removed a primary nest in Witikon and a secondary nest at a forest edge in Schwamendingen last year, and by mid-July this year had already logged four primary nests. A nest was also found in the Eigental reserve near Kloten, and the canton says it is now drawing up criteria for which nests to destroy first in sensitive habitats. Canton Aargau, further along the Rhine, had sightings of the hornet as early as 2022 and 2023. Anyone who sees a dark hornet with yellow feet on the Swiss side can report it, with a photo, at asiatischehornisse.ch; on the Baden-Württemberg side, the state nature conservation administration runs a reporting portal. Spring is when the small primary nests on buildings are easiest to find and remove, but the coming weeks of leaf fall are when the big canopy nests finally show themselves.

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.

Red-legged frogs settle into summer refuge as bullfrogs share their hills

Early September is the part of the year the California red-legged frog (Rana draytonii) spends away from water. Breeding ran from November into April. By now most adults have left the ponds and moved into the surrounding hills, sitting out the dry months under rocks, in leaf litter, in animal burrows, or down in the cracks of a pond bottom that has already dried. A frog can travel a mile overland in wet weather and settle two miles from where it bred. The sightings logged this month, from the park canyons of San Francisco down the Pacifica shore around Sharp Park and north across the Golden Gate into the Mount Tamalpais hills, are single frogs in refuge, not a gathering at any one pond. It is the largest frog native to California, up to four and a half inches from snout to rump. The back is reddish brown to olive with irregular dark blotches. A raised ridge of skin runs along each side from behind the eye to the hip. A dark mask crosses the face above a pale stripe on the upper lip. Turn one over, or catch it mid-leap, and the belly and the undersides of the hind legs are washed in red; that is the name. Young frogs may show yellow there instead of red, with heavier spotting on the back. Two other frogs share these hills. The Sierran treefrog is a fraction of the size, two inches at most, with toe pads and no side ridges, and it owns the loud two-part ribbit of the movie soundtracks. The red-legged frog's own call is a low, stuttering grunt that carries poorly. The American bullfrog is the one to look at hard. It is bigger, green about the snout, with a very large eardrum behind the eye, and it lacks both the side ridges and the pale lip stripe. Its call is the deep jug-o-rum. The bullfrog matters for more than identification. It was introduced to California, it breeds over a longer season, and its tadpoles eat red-legged frog eggs and tadpoles. In one study, red-legged frog larvae sharing a pond with bullfrog tadpoles survived at under five percent, against thirty to forty percent where bullfrogs were absent — the proposed mechanism is direct predation by bullfrog tadpoles and juveniles on red-legged frog eggs and larvae, plus competition for the same shallow-water habitat. Not every study finds that pattern; some point out that bullfrogs tend to turn up where ponds have already been altered, so the two effects are hard to pull apart. Bullfrogs were logged through the same weeks this summer around Mill Valley and Lake Lagunitas, in the same Marin hills as one of this month's red-legged frog records. Whether the two share any particular pond is not something the records show. What the red-legged frog needs from a pond is specific. Eggs go into shallow water at the vegetated edge in loose clusters and hatch within two weeks. The tadpoles then take three and a half to seven months to become frogs, so a breeding pond has to hold water from winter into summer. It also has to stay cool. The frog cannot survive water above 29 degrees Celsius (about 84 F), and ponds with willows and cattails standing over deep water do best. The emergent plants do double duty: they hide tadpoles from herons and fish, and they warm the shallows enough to grow the algae the tadpoles feed on. The species is listed as threatened under the federal Endangered Species Act, and mapped critical habitat overlaps the Peninsula. Anyone who finds one of these frogs this fall, under a board or beside a seep well away from open water, is seeing the non-breeding phase that can take up as much as eleven months of its year.

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.