Dissolved oxygen hits new low as thermal stress peaks
July 11, 2026
Dissolved oxygen dropped to 3.6 mg/L today—the lowest reading yet this month, sliding further below the already worrying 3.9 recorded just five days ago. A sudden flow pulse brought 35 cubic feet per second through the creek, a seven-fold spike from the sluggish 5-foot-per-second average that has prevailed for two weeks. But the pulse arrived far too late: midsummer thermal loading has run so deep that one surge of cooler water cannot reverse it . Speckled Duns ( Callibaetis spp.) have been holding steady throughout the area all month—sightings from late June into early July across the lower reaches. These mayflies thrive in moderate flow and good oxygenation; their presence here now underscores what these collapsing conditions are working against. Water temperature climbed to 20.6°C, and while pH remains neutral at 7.5, the oxygen deficit alone threatens the cold-water invertebrate community that has persisted through drought and low flow.
Pale Snaketail emerges in urban river under dissolved oxygen stress
July 20, 2026
Pale Snaketail dragonflies emerged this month along the South Platte River — a finding that carries weight in an urban waterway. These elegant damselflies ( Gomphus pallida ) require clean, well-oxygenated streams with gravelly bottoms to complete their aquatic nymph stage, which typically spans two to four years buried in sediment. A single adult snaketail is therefore a window not into this season's conditions, but into water quality that held steady years in the past, when that nymph was developing. That context makes the current crisis harder to reconcile. Dissolved oxygen in the creek system has collapsed this month, plummeting to 2.8 milligrams per liter — well into lethal stress for most aquatic invertebrates. Whether the larva that became this adult found a cleaner refuge upstream, or simply experienced milder conditions before the freefall, remains unknown. What is clear is that the broader dragonfly community — Widow Skimmers , Common Green Darners , Blue Dashers , and a dozen other species active in the parks and ponds along the Platte — reminds us how much ecological work these urban water bodies still perform. Even as the river itself teeters, they hold.
When hummingbird meets beardtongue
May 22, 2026
The morning air holds the cool of late spring in Park Hill, where cottonwoods spread their new leaves and willows release clouds of pollen. Step outside if you can. Close your eyes and listen for the sound that cuts through the bird chorus: a metallic trill, sharp and insistent, followed by silence. That trill belongs to a Broad-tailed Hummingbird (Selasphorus platycercus), and the silence is the bird hovering. Right now, as May deepens toward June, these hummingbirds are establishing territories and beginning to nest. The males arrived first from their wintering grounds in Mexico, staking out the best feeding spots. The females followed, evaluating both mates and real estate. What they both seek, urgently, are the tubular purple flowers of Broadbeard Beardtongue (Penstemon angustifolius). These native wildflowers bloom in tight synchrony with the hummingbirds' arrival, their peak flowering timed to fuel the birds' most energy-intensive season. The beardtongue opens its flowers in clusters along tall stems, each bloom a perfect fit for a hummingbird's bill and tongue. The flower's architecture excludes most other visitors. Bees cannot reach the nectar at the base of the long tube. Butterflies lack the hovering precision the narrow opening demands. But a Broad-tailed Hummingbird approaches each flower like a key finding its lock. The bird inserts its needle-thin bill deep into the tube, its forked tongue flicking out to lap nectar from the base. As it feeds, pollen dusts the crown of its head and the base of its throat. When the hummingbird visits the next beardtongue, that pollen transfers, completing the exchange that has sustained both species across thousands of springs. This partnership operates on precision timing. The beardtongue cannot afford to bloom too early, when late frosts might kill the flowers, or too late, when the hummingbirds have already committed to other nectar sources. The hummingbirds cannot arrive before their primary fuel appears, but they also cannot wait too long, or the best nesting sites will be taken by competitors. Female Broad-tailed Hummingbirds are building their nests now, gathering spider silk and plant down, shaping cups barely larger than a walnut. Each nest represents thousands of trips to beardtongue flowers, each feeding bout converting nectar into the energy needed to incubate eggs and feed young. The beardtongue, in turn, depends on this intensive visitation. Other pollinators visit sporadically, but hummingbirds work systematically, moving from flower to flower within a patch, then traveling between patches, ensuring genetic diversity in the plant's reproduction. Look for the beardtongue in open areas where the soil drains well, its purple spikes rising above shorter grasses. Listen for the hummingbird's trill, often heard before the bird is seen. If you spot the flash of metallic green and the ruby throat of a male, watch how it moves between flowers. The feeding is methodical, efficient, each visit lasting only seconds before the bird moves on. The sound of its wings shifts as it hovers, a higher pitch than the trill of its territorial call, steady as a small motor running in the morning air.
