Within One Watershed:

Essays from Hackleman Creek

Part 2

The Valley

Knee-deep in Hackleman Creek

Despite its name, Tombstone Prairie pulses with life this morning. As my friends and I skirt this small meadow near the headwaters of Hackleman Creek, bees buzz from one flower to the next, grasshoppers leap across the path and an Evening Grosbeak forages for insects near the top of a tree, its bold yellow plumage standing in vivid contrast to the conifer’s deep green.

Named for the stone monument that marked the spot where a teenaged boy died in an accidental shooting in 1871, the clearing was a popular camp spot for European-American settlers traveling between the Willamette Valley and eastern Oregon. Prior to that the meadow was a traditional stopover for countless generations of Indigenous peoples on their seasonal rounds of hunting and gathering. Back then, this open area was much larger thanks to the Native American practice of regular burning to promote huckleberry growth and grazing areas for game animals. A century and a half of fire suppression has allowed many trees to encroach on the meadow. Some huddle in small groups among the bracken ferns and grasses; others stand alone, casting solitary shadows on the peach-colored Jacob’s ladder blossoms covering the ground.

Enticing as it is, Tombstone Prairie is not the object of our focus today. Wearing old tennis shoes and rubber boots, our trio is here to investigate the creek, knee-deep if necessary. We’re in search of tiny aquatic creatures that form the foundation of a stream’s food chain. They’re called macroinvertebrates: they lack backbones and are small, but not small enough to require a microscope for viewing. We hope to find mayfly, stonefly and caddisfly larvae, the species most sensitive to pollution; their presence in a stream indicates good water quality and a healthy aquatic ecosystem.

Reaching the midpoint along the northern margin of Tombstone Prairie, we meet the creek. At this point the spirited current carries water newly issued from the spot where it gurgles out of the mountainside, a few hundred yards upstream. Shallow and narrow enough to step across, the creek will gain depth and width as it receives the flow from several side streams along its course down the valley. Here, the newborn stream splashes over a four-foot waterfall, slides between tree roots and bounces gently over bagel-sized cobbles.

Resting my palms on the rocky creekbed, I let the chilly water wash over my hands; goosebumps rise on my arms. Looking into the creek, I notice small pebbly cylinders, no more than an inch long, speckling the submerged rocks; they are the protective coverings of case-maker caddisfly larvae. In its larval stage, a caddisfly is a caterpillar-like creature that scrapes algae from rocks in the stream. Each larva gathers tiny pebbles and sand grains from the bottom and glues them to its body with silk from glands near its mouth. It then crawls slowly over rocks to search for sustenance, safely cloaked in armor. The caddisfly spends up to two years in this larval form, then seals both ends of its case and pupates in an underwater cocoon. After two to three weeks, it emerges from its casement, rises to the surface and flies away as a moth-like adult.

In fact, caddisflies are closely related to butterflies and moths. I think of their butterfly cousins flitting 1,200 feet above us in search of mates and wildflower nectar atop Browder Ridge. I look down at a caddisfly case and think of the butterfly chrysalis I found not long ago hanging in a tiny cleft high on the ridgecrest. These larval creatures, one bound to the streambed and the other to the rocky heights, evolved from the same ancestor in the distant past. Each took a different route to their present ecological niche; their presence in the watershed is the sign of an untainted ecosystem.

Moving downstream, one of my companions finds another type of macroinvertebrate – a mayfly nymph. As she holds the rock upon which it squirms, I see a slim body separated into three parts: a flattened head, a dark thorax and a long, segmented abdomen. Three filamentous tails extend from its back end. Each of its six legs ends in a tiny hook for clinging to rocks in rushing water.

Seconds later, my other friend finds an adult mayfly resting on a boulder and gently guides it onto her thumb. Holding its fragile wings in an upright position above its slender body, it lifts its elongated abdomen and head like a winged ballerina performing a perfect arabesque. All six legs are the same length, indicating this delicate dancer is a female. Males have extremely long front legs for grasping females while mating.

As a nymph this female shed her skin dozens of times, emerging a little larger with each molt. She spent over a year crawling underwater in search of algae to eat, using her brush-like lower lip to scour it off of rocks. Eventually, she rose to the surface and molted again, this time emerging as a sexually immature subadult. Hours later, one last molt released the mature female mayfly. Her adult life will only last for 24 hours: she won’t even be able to eat, as she has no functional mouthparts; her sole purpose is to reproduce. Later today, as afternoon fades into evening, she will join a swarm of other adult mayflies for a communal courtship dance in the sky. After mating, she will lay hundreds of eggs and die, her mission accomplished. My friend carefully returns the little female to her boulder so she can carry out her short but intense adult life.

We head downstream to find a stretch where the water runs deeper. As my friends climb down below a footbridge, I wade up to my knees. A thin layer of biofilm covers each melon-sized rock like slippery mucus; this organic slime sustains hungry macroinvertebrates and makes each step a challenge for me. I carefully wedge each foot in a flat spot between rocks and lower my hands into the current. An American Dipper flies low over the water and lands on a midstream rock. The gray robin-sized bird bobs up and down as it eyes the flow. Suddenly it plunges in and walks upstream completely submerged, resurfacing with a beakful of mayfly nymphs. As the stream-dwelling songbird flies to the bank to enjoy its meal, an adult mayfly flutters above the surface, repeatedly dipping her abdomen into the water to release a small batch of eggs each time. Fortunate to have evaded predators, she gives the next mayfly generation its start.

Joining my friends below the bridge, I see they have two more discoveries to share: stonefly and dobsonfly larvae. The stonefly larva looks like a flattened cricket with a three-part body, widely separated eyes, long antennae, six sprawling legs and two thin tails. The finger-sized dobsonfly larva resembles an aquatic centipede. Thread-like gills line each side of its abdomen; its reddish head sports two strong pincers for capturing prey. Both these species are highly sensitive to pollution. Our discoveries today confirm that the Hackleman watershed, my watershed, flows clean and pure, supporting a robust assemblage of underwater inhabitants. May its purity continue to sustain this richly complex community for generations to come.

Next time: We leave the valley and explore Fish Lake.