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.
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.
Killdeer nest guards the grassland edge
May 21, 2026
The cottonwoods along Denver's urban waterways have pushed out their first broad leaves, and the switchgrass sends up new shoots through last year's weathered stems. In the open ground between water and woodland, where gravel meets grass and human paths cross animal trails, the killdeer (Charadrius vociferus) stakes its claim to the season's most exposed real estate. This plover builds no nest. The female scrapes a shallow depression in bare soil or sparse grass, sometimes lined with a few pebbles or bits of debris, and settles her four buff-colored eggs directly on the ground. The eggs blend so perfectly with their surroundings that even a careful observer can walk within feet without seeing them. What you cannot miss is the parent bird's response to your presence. The killdeer launches into one of nature's most convincing performances: dragging a wing as if broken, calling in apparent distress, leading you away from the nest site with every appearance of vulnerability. This broken-wing display draws potential predators toward what seems like easy prey, while the eggs remain hidden in their shallow scrape dozens of yards behind. The deception works because it exploits a predator's instinct to pursue the easiest target. A fox, hawk, or curious human follows the seemingly injured bird, which stays just out of reach, wing dragging pitifully. Once the threat has been led far enough from the nest, the killdeer miraculously recovers, flies strongly back toward its territory, and resumes normal foraging behavior. The performance is so convincing that even experienced birders find themselves momentarily concerned for the bird's welfare. But this is calculated theater, refined over thousands of generations of ground-nesting survival. Killdeer choose these marginal spaces because they offer both advantages and challenges that other birds cannot navigate. The open ground provides clear sightlines for spotting approaching danger, while the sparse vegetation offers just enough cover for camouflaged eggs. These edges between habitats attract the insects that killdeer feed on: beetles, grasshoppers, and fly larvae that thrive where soil meets grass meets water. The birds probe and pick through the earth with quick, precise movements, their long legs allowing them to wade through shallow puddles and navigate uneven terrain. During this nesting season, both parents share territory defense and chick-rearing duties, though only the adult performing the distraction display will risk everything to protect the clutch. If you find yourself walking these transitional spaces where pavement gives way to prairie, where storm runoff creates temporary wetlands, listen for the killdeer's namesake call echoing across the open ground. The sound carries farther than you might expect, a clear announcement of presence and territory that cuts through the morning air. Watch for the flash of white on dark wings as the bird moves between feeding and guarding, and notice how it chooses the most exposed, seemingly vulnerable spots to make its stand.
