“Dipper!” I called to the group and set up the scope for looks. It seemed easier than usual to share views of this bird—it remained still, perched on the rocks rather than dunking its head, bobbing along the surface, and plunging headlong into the creek as they usually do. Instead, it stayed perfectly immobile. “The dipper isn’t dipping,” someone remarked. I had primed the group, some of whom had never seen a dipper, for its eponymous behavior: constant dipping up and down as it bent at the knees, seemingly for no reason.
Scientists have been pondering this dipping for some time. Some species will bob, like a Rock Wren, or teeter, like a Spotted Sandpiper, but nothing dips quite like a dipper—not even some dippers. There are five species of dipper in the world, and two, the South American species, don’t dip. They are also the only ones that don’t habitually forage underwater.
This coincidence, of these two being so different from their three cousins, hints strongly at what I have always thought to be the most convincing argument for why dippers dip—they’re trying to see into the water, or at least gain some depth perception of the rapid waters they are about to enter.
Another reality of life for most dippers is that they often occupy noisy environments full of riffles and rapids. While their calls cut through the droning water, maybe the dipping is an easier way to advertise where you are if you’re a dipper—after all, there’s only so much good habitat for a dipper, and they’re accordingly territorial.
The last argument I’ve heard for dipping is that it’s somehow a predator deterrent, but I’ve never been quite sure how that would work.
As the group pondered these questions, a hand went up and pointed to an overhead raptor. We watched as it flew away from us and cruised into a stand of dense trees some 100 yards downstream. Following the bird the whole way, we could see the long tail, steady flight, and large size of a Cooper’s Hawk.
As our attention turned back to the dipper, we noticed a little half dip. Then another. And another, as it gradually returned to its regular dipping routine, wandered to the water’s edge, and poked its head in.
Slowly, recognition washed over us. Had the dipper seen the Cooper’s Hawk before any of us had? Every birder has been humbled by how much better birds are at finding predators than we are (the survival imperative is a hell of a drug).
More intriguingly, had the bird frozen because it had seen the Cooper’s Hawk? Had we just seen this bird disprove one of the theories on dipping, in real time?
We posed the question aloud, but before we were able to take ourselves too seriously—“Ooh, it dove in!”—we got back to the simple pleasure of watching a dipper dive and swim and hop and run.
