Ospreys hunt the summer shallows

The Gunnison River runs cold and clear through mid-summer, dropping off its spring flood levels and settling into the kind of water an osprey can actually read. At this flow, the shallows along the inside bends are knee-deep on a person, and the trout that hold in them are visible from thirty feet up if the light is right and you know what you're looking for. The ospreys know.

Ospreys are fish specialists — more precisely so than almost any other bird of prey on this continent. Their diet is fish, nearly exclusively, and everything about their hunting apparatus reflects that. The feet have a reversible outer toe, so they can grip with two toes forward and two back, clamping a fish from both sides rather than from one. The soles of their feet are covered in short, curved spicules that grip wet, slick scales the way a rough surface grips ice. When an osprey hits the water, it enters feet-first from heights of ten to forty feet, sometimes submerging completely before pulling back out. The whole strike, from the moment the bird folds and drops to the moment it clears the surface, takes less than two seconds. If you're watching one work a stretch of river and you blink at the wrong moment, you miss it.

In Gunnison, the fish they're after are cutthroat trout. Cutthroats are the native trout of this drainage, a fish that has been here long enough to shape the habits of every predator that eats fish in these mountains. They hold in predictable lies — behind boulders, along current edges, in the tail-outs of pools where water slows and oxygenates. An osprey hunting the Gunnison learns these locations the same way a good fly fisher does, by watching the water until the pattern becomes readable. The trout the ospreys take most often are juveniles and mid-size fish, not because the birds can't handle a large cutthroat, but because a two-pound fish is easier to carry and doesn't fight long enough to be a liability in the air.

This time of year, the ospreys along the Gunnison are likely hunting in small family groups. Fledglings from this season's nests are now on the wing, and the adults are still feeding them, or at minimum hunting alongside them as the young birds develop their own technique. A juvenile osprey can fly before it can fish. The hunting itself takes practice — reading water depth, accounting for the refraction that makes a fish appear shallower than it is, timing the stoop correctly. Young birds miss more than they catch for weeks. They watch adults make the same approach, make the same adjustments, come up with fish again and again, and gradually their accuracy improves. By the time they begin their first migration south in late summer, they need to be self-sufficient. The adults won't be with them.

The river conditions right now favor this kind of hunting. Water temperatures in the Gunnison are running around 11 or 12 degrees Celsius — cold enough to keep the cutthroats metabolically active and feeding, which means the fish are moving and visible rather than holding deep and still. Flows have dropped from spring peak, reducing the turbidity that makes visual hunting difficult. An osprey working a riffle under mid-summer sun has good sight lines into the water column, and the fish, feeding on the summer insect hatch, are in the shallows.

If you're near the river right now, look for a large bird hovering in place above the water, wings beating steadily while the body stays nearly still. That hover is the osprey reading the water below, fixing on a target before committing. Sometimes it repositions — drops a few feet, shifts twenty yards upstream, hovers again. Then it folds, and drops. The splash, when it comes, is loud and abrupt. The bird that comes back up is heavier, rearranging its grip mid-flight to orient the fish head-forward into the wind before carrying it off to eat or to bring to a waiting juvenile somewhere in the cottonwoods along the bank. The river surface settles back into its current as if nothing happened.