Bank swallows and the insect emergence
June 7, 2026
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.
Magnolia warblers time their return to spring leaves
May 23, 2026
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.
Female monarchs arrive to find milkweed in flower
June 25, 2026
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.
