Southeastern Wisconsin Till Plains

The Schmitz Ready Mix facility in Milwaukee, located roughly 15 kilometers inland from the lake plain, is now listed by EPA in significant non-compliance with its Clean Water Act discharge permit. The facility exceeded at least one monthly average pollutant limit; the compliance record doesn't specify which pollutant or by how much, only that the exceedance is on the books and the case remains open.This is a distinct matter from the combined-sewer overflow violations at the Milwaukee Metropolitan Sewerage District reported here in July. The two permit holders aren't connected findings, just separate dischargers drawing regulatory scrutiny in the same watershed within a single season, which says more about the intensity of oversight on this stretch of the Southeastern Wisconsin Till Plains watershed than about any single facility.For scale, EPA's most recent impaired-waters assessment covering Bradford Beach, Atwater Beach, Milwaukee Harbor, and dozens of other area waterbodies currently lists all of them as not impaired, though many carry data gaps for some designated uses. That assessment predates this violation and doesn't account for it, so it can't be read as evidence one way or the other about conditions near the Schmitz outfall specifically. What's on record is simple: a permitted discharger exceeded its limit, and the question of what that means downstream, and for how long, remains open.

Thirty-nine research-grade sightings of the rusty patched bumble bee were logged across the Kettle Moraines area in the past 30 days. That is the same figure from both available sources — iNaturalist's species roster and the individual observation records — pulled over the same 30-day window and the same 25 km radius. The dates fall in the late-summer stretch when colonies are provisioning new queens before the season ends. Bombus affinis was once common from the upper Midwest into the Northeast, but its range has collapsed by an estimated 90 percent since the late 1990s, and it was listed as federally endangered in 2017, the first bumble bee species in the continental United States to receive that status. A few strongholds remain, and this stretch of southeastern Wisconsin, with its mix of oak savanna, prairie remnant, and undisturbed ground for nesting and overwintering queens, is one of them.Queens of this species need to keep finding nectar and pollen right up until they enter diapause for the winter, so a bee spotted now is doing some of the most consequential foraging of its whole life cycle. She is building fat reserves that have to carry her through months underground, alone, before she can found a colony next spring. But the count itself should not be read as a trend. Eight of the 39 records come from Greenfield Park in West Allis and several more from a single address in Waukesha, so the number tracks where people are out looking at least as much as where bees are. What these records establish is presence and activity across the landscape right now — not that the population is stable, growing, or larger than last year.Separately, and worth noting without overstating its connection to the bees: the ESSENTIAL INDUSTRIES INC facility is currently listed in significant non-compliance with its Clean Water Act permit. The violation on record is administrative — a missed discharge monitoring report — rather than a documented pollutant exceedance, so there's no evidence here of a chemical discharge affecting habitat or water quality. It's a reminder that regulatory oversight in this landscape is uneven, but it shouldn't be read as a threat to the bumble bee population itself.Anyone walking these trails who spots a bumble bee with the telltale rusty patch on its abdomen can help simply by logging it on iNaturalist. Every confirmed record adds to a thin and valuable picture of where this species is still holding ground — and records from less-visited corners of the moraines are the ones that fill the real gaps.

Nearshore water temperatures have dropped sharply to 16.5°C this week — a plunge of more than ten degrees from the dangerous highs of a month ago, when tributary streams were pushing the thermal limits for cold-water fish. The shift is driven by a classic summer upwelling: persistent southwesterly winds push the warm surface layer offshore, pulling cold, deep water up along the shoreline in its place. The change can be dramatic — sometimes dropping temperatures ten degrees in a single day.Alewife strandings documented from Milwaukee Bay south to Wind Point through June fit this pattern closely. These introduced forage fish are acutely vulnerable to the thermal shock that upwelling delivers—the phenomenon was implicated in the catastrophic beach die-offs of the 1960s that ultimately prompted the stocking of Pacific salmon as a biological check on their population. For lake trout stressed by heat in tributary streams all summer, the cold plume offers a brief reprieve — though it is temporary, a seasonal rhythm rather than a rescue.

Four sightings of Giant Mayfly (Hexagenia limbata) along the Milwaukee riverfront between late May and early July — at Riverside Park and the Hank Aaron State Trail — mark something that would have been unthinkable to a mid-century naturalist: these insects are back in water where they were once erased entirely. The river measured 17°C at time of observation, well within the cool, oxygenated conditions giant mayflies demand, and the emergences themselves, in both location and timing, carry the hallmarks of a reproducing population rather than isolated strays. That is genuinely good news, and it deserves to be understood against the full history of what happened here.Giant Mayflies in the genus Hexagenia were functionally eliminated from southern Lake Michigan by the mid-twentieth century — not by overharvest or habitat loss in the conventional sense, but by suffocation. Untreated industrial and municipal waste flowing into the lake consumed the dissolved oxygen in bottom sediments, and giant mayfly nymphs, which spend up to two years burrowing in fine lakebed muds and filtering organic matter, simply could not survive the resulting dead zones. Their disappearance was so complete that it registered as a threshold collapse, the kind ecologists use as a before-and-after marker for an entire system's health. The passage of the Clean Water Act in 1972 and the subsequent buildout of wastewater treatment infrastructure began to reverse that collapse, and by the 1990s and early 2000s, researchers were documenting the first tentative recolonization pulses moving southward through the lake basin.What makes this summer's sightings complicated — and why they cannot be read as simple victory — is that the watershed feeding this shoreline remains under active stress. The MILWAUKEE METRO SEW DIST COMBI combined sewer system is currently in significant non-compliance with its Clean Water Act permit, meaning that during heavy rain events, untreated sewage and stormwater are still being discharged directly into receiving waters. The Menomonee River, one of the two main river systems draining into this shoreline stretch, carries an official impairment listing — a formal acknowledgment that it is not meeting basic water quality standards. Giant mayfly nymphs are exquisitely sensitive to low dissolved oxygen and fine-sediment quality; the same conditions that once wiped the species out regionally are, in a less acute form, still being generated by overflow events today.The giant mayflies have returned to a system that has not yet returned to them. That asymmetry is the defining ecological tension of this moment on the riverfront. Giant mayflies are recolonizing the margins of a recovery that remains incomplete, and whether these populations persist and expand or contract back will be determined in large part by what happens in the sediment over the next several years — how often anoxic pulses reach the river bottom, how much fine organic waste accumulates, and how reliably cool, oxygenated conditions hold through summer. The species is doing the work of a bioindicator whether we ask it to or not.The broader ecoregional context matters here too. This riverfront sits within the Lake Michigan Lacustrine Clay Plain, a landscape shaped by glacial lake clays that drain slowly, concentrate runoff, and amplify the downstream effects of urban impervious surfaces during storm events. That geology is not incidental: it is why combined sewer overflows here carry such ecological weight, and why summer storm intensification — already a documented trend in the Great Lakes region — poses a compounding threat. As the season's heavier rains arrive, the sightings record here will become a real-time legibility test for how much the system can absorb before the recovery signal at the riverfront dims again. Watch the emergence windows carefully through July.

Water temperatures have climbed to 26.6°C, entering the seasonal window when ammonia becomes acutely toxic to fish — and two upstream sanitary districts have been discharging far above their permitted levels. St. Joseph Sanitary District ran more than four times its ammonia limit in the fourth quarter of 2025, with exceedances continuing through spring at 58 percent over permit. Milwaukee Metro Sewer is also in significant noncompliance. Neither facility has faced penalties.The two rivers draining this landscape are already federally listed as impaired — 18 of 40 assessed stream segments in the area carry that designation. Summer is when stressors compound: heat accelerates ammonia's toxicity, while high discharge volumes stretch treatment capacity. The margin between technical noncompliance and ecological failure narrows week by week.

River temperatures have climbed to 28°C as streamflow has nearly ceased, concentrating heat and dissolved nutrients in waterways already listed as impaired. This is the moment when oxygen levels collapse. Chinook salmon and trout in these tributaries are now well past their thermal stress limits — unable to extract sufficient oxygen from water this warm, their metabolic demands climbing even as the available oxygen falls. The conditions that looked tolerable a few weeks ago have turned acutely hostile.This convergence of heat, low flow, and pre-existing water-quality impairment creates a lethal window. Recovery depends on rain that breaks the drought and restores stream volume — but that relief cannot come too late.

Kelp Gull (Larus dominicanus), a seabird native to the Southern Hemisphere, has appeared at Jones' Island seven times between late April and mid-June—an unusually long residency for a species found thousands of miles from its typical range. Each sighting was documented and research-grade, suggesting a single committed bird rather than casual vagrants.What makes this observation especially significant is the appearance of a Kelp x Herring Gull hybrid on June 12—strong evidence that the Kelp Gull has been ranging widely enough throughout the spring to interact with the resident flock. The bird's tolerance of Great Lakes conditions and apparent social integration with local gulls raises questions about shifting range boundaries and whether warming water temperatures are creating new niches for Southern Ocean specialists.

Butterfly milkweed is blooming in the Milwaukee area right now, its flat-topped clusters of small orange flowers open in the sun. The plant grows low, rarely more than a foot or two tall, in dry and well-drained spots: roadsides, prairie remnants, open patches where the soil is thin. If you are near one of those places, look for a butterfly that is larger than it first appears, orange and black with white-edged wings, moving deliberately from plant to plant. That is a female monarch, and she is not here for the flowers.Monarchs will drink nectar from many plants, but they can only reproduce on milkweeds. Butterfly milkweed is one of the species they use, and in this region it flowers in early summer, which is when the first females are arriving from the south. A female lands on a milkweed stem, walks it slowly, pressing the underside of a leaf with her forelegs. She is tasting it. Her feet carry chemoreceptors that can detect the compounds in milkweed tissue, and she is confirming that the plant is the right species before she commits. If it is, she curves her abdomen beneath the leaf and deposits a single egg, pale green and ribbed, about the size of a pinhead. Then she moves to the next plant, the next leaf. She will lay hundreds of eggs over the course of her adult life, almost never more than one per plant, spreading the risk across the landscape.The egg hatches in three to five days. The caterpillar that emerges eats milkweed and nothing else. Butterfly milkweed, like all milkweeds, produces latex, a sticky white sap loaded with cardenolides, which are compounds toxic to most insects and vertebrates. Monarch caterpillars are not affected by them. They feed on the leaves, accumulate the cardenolides in their own tissue, and carry that chemical defense through metamorphosis into adulthood. A bird that eats a monarch gets sick. Most birds that have had that experience avoid the orange and black pattern afterward. The defense depends entirely on access to milkweed during the larval stage, which is why the female's host-finding behavior matters as much as it does. No milkweed, no caterpillars.Butterfly milkweed is a native plant that has become less common across the Midwest as grasslands and open habitats have been reduced or taken over by invasive species. Dame's rocket, an invasive that is blooming in purple and white drifts along roadsides and disturbed edges throughout this area right now, occupies some of the same disturbed ground where butterfly milkweed might otherwise establish. The competition is not direct, but the pattern is familiar: native plants that need open soil and full sun lose ground when that habitat fills in, whether with invasives or with woody vegetation. Butterfly milkweed persists where it has been planted in gardens, in restored prairie patches, and in the drier margins of parks. Monarchs find it in all of those places.The relationship between monarchs and milkweed is often described as simple, but the timing makes it complicated. Monarchs that overwintered in Mexico began moving north in spring, breeding as they went. The females arriving here now are likely the daughters or granddaughters of those overwintering adults, raised on milkweed further south and then continuing the northward movement. They need milkweed to be available when they arrive, which means the plant's flowering schedule and the insects' migration schedule have to align. In a year with a warm early spring, milkweed may flower earlier than usual. In a cool year, it may lag. The monarchs adjust somewhat, but the window is not unlimited.Somewhere nearby, if the light is good and the air is warm, a monarch may be working the edges of a sunny patch right now, pausing on each milkweed plant just long enough to check it before moving on. The orange of the butterfly and the orange of the milkweed flowers are close enough in color that the two can be hard to separate at a distance. Watch for movement: the slight, deliberate shift from stem to stem that distinguishes an egg-laying female from a butterfly simply feeding.

The Milwaukee River carries the sound of water over stone, but if you listen closely near the Historic Financial District, you'll hear something else threading through the air above. Sharp chips and chatters mark the flight paths of bank swallows as they work the space between water and sky. These smallest of our swallows have claimed the vertical banks along the waterway, where their tunnel nests honeycomb the exposed earth like a apartment complex built for speed.Bank swallows are brown above and white below, with a distinct brown band across the chest that separates them from other swallows in flight. They fly with quick wingbeats and sudden turns, following insects invisible to us but abundant in the warm air of early summer. Right now, in the longest days of the year, they are feeding young hidden deep in those tunnels. Each pair excavates a burrow that can extend three feet into the riverbank, ending in a chamber lined with grass and feathers where four or five white eggs become hungry mouths that demand constant attention.The timing is not accidental. Early summer brings the great emergence of aquatic insects from the Milwaukee River. Mayflies, caddisflies, and midges complete their underwater development and rise to the surface by the millions. They shed their nymphal skins and take to the air just as the swallows need them most. A single bank swallow chick requires hundreds of insects each day, and the parents make trip after trip from river to nest, their throats bulging with captured prey. The insects emerge in waves throughout the day, but the heaviest flights often come at dusk when the air cools and the water releases its stored warmth. You might see the swallows working these emergences, dozens of birds wheeling and diving in coordinated hunting flights that can stretch for half a mile along the river.The colony nests in loose synchrony, most pairs laying eggs within a few weeks of each other. This timing ensures that the peak feeding demands of all those growing chicks align with the peak abundance of emerging insects. The swallows have only one chance each year to raise their young here before they begin their long migration to South America. They cannot afford to miss the emergence. When the insects rise, the swallows are ready. When the emergence wanes in late summer, the birds will follow the retreating abundance south, leaving behind empty tunnels that will collapse with the first hard rains of fall.Listen now for their voices above the water. The calls are sharp and social, birds communicating the location of insect concentrations to others in the colony. If you're standing where you can see the river, watch for their flight pattern: quick bursts of wingbeats followed by brief glides, sudden direction changes that track the movement of prey too small for you to see. The air itself tells the story of abundance in early summer, written in the language of wings and hunger, emergence and provision. The swallows read it fluently, and their success is measured in the steady stream of insects disappearing into tunnel mouths carved into the living bank.

The alternateleaf dogwood breaks its buds along the understory edges of Estabrook Park, each tight cluster unfurling into the soft green of early leaves. The timing is precise. Small insects emerge as the leaves expand, drawn to the fresh surfaces and the shelter they provide. Above them, a flash of yellow catches the light between branches.Magnolia warblers have returned from Central America to breed in these newly leafed canopies. The males arrive first, their black necklaces bold against bright yellow throats, white wing patches flashing as they move through the dogwood and swamp white oak. They time their arrival to match the exact moment when the understory trees break dormancy. The insects they need are emerging with the leaves. Aphids cluster on tender dogwood shoots. Small caterpillars begin their work on oak buds just opening to full size. The warblers move methodically through this fresh abundance, gleaning insects from leaf surfaces, plucking them from bark crevices, occasionally darting out to catch something in flight.The alternateleaf dogwood provides more than food. Its horizontal branching creates the layered structure magnolia warblers prefer for nesting. The female will build her cup of twigs and grass in a fork ten to fifteen feet up, often where dogwood branches meet the trunk of a larger tree. The dogwood's white flower clusters are opening now, drawing more insects to the immediate area. The tree's broad leaves will soon provide cover for the nest and shade for the nestlings. This is not coincidence. The warbler's entire breeding cycle synchronizes with the dogwood's spring growth. Eggs hatch when insect abundance peaks in late spring. Young fledge as summer insects reach their greatest numbers.Other understory trees join this partnership. The swamp white oak's leaves are expanding now, their surfaces already hosting the tiny larvae that will feed warbler nestlings. Common lilac, though invasive, blooms in full purple clusters nearby, its flowers attracting different insects that add to the warbler's menu. The male magnolia warbler sings from these mixed canopies, his sweet notes rising and falling as he moves between feeding and territorial display. The female remains quieter, focused on the careful work of selecting nest sites among the dogwood's spreading branches.Listen for the male's song if you are walking beneath leafing trees. His voice carries clearly in the still air of late spring mornings, a series of musical phrases that seem to celebrate the exact moment when winter's grip releases and the forest returns to green abundance. The alternateleaf dogwood's leaves rustle softly overhead, each one a small flag marking the season's turn.