Monday, November 10, 2008

The Water Ouzel, an Ecological Indicator

American Dipper - Photograph by Tom Kennedy

We donned our cross-country skis at the East Fork of the Jemez River, expecting nothing much more than a glorious winter outing in a beautiful canyon. Brilliant sunshine belied the actual temperature as clouds of condensation fogged our glasses. The novice among us worried about the skill level required for the outing, as she clipped her spankin’ new boots in to her equally virgin cross country skis. As a winter wonderland, the Jemez back country is easy to access and provides a more solitary experience than the crowded trails of the Sandia Mountains. Only two more cars shared our space, an indicator of the near solitude that awaited.

As we neared the river, a flash of gray in motion caught my eye. A quick flit, and the bird disappeared behind the rocks. It was February, a month where our usual avian companions are the hardy ravens and Steller’s Jays. Most humans would not be expecting a birdwatching expedition but it soon became apparent that this outing would reveal special rewards. Cautiously, and as quietly as possible, we sneaked up to get a better view of the elusive gray bird whose plumage blended so well with the wet rocks. Only rippling, crystal clear water cascaded through the stream that drained the Valles Caldera. However, as we watched, a little gray bird popped up from beneath the surface with an aquatic insect firmly clutched in its bill.

First documented and christened “Water Ouzel” by John Muir, bird and stream once were considered inseparable. Present along fast-moving, clear, unpolluted mountain streams in the American West throughout the year, the American Dipper is almost exclusively associated with water. The behavior and biological adaptations of this aquatic bird are unique, combining aspects of songbirds with those of ducks. Their traits include and incessant dipping, hence the current name, and a blinking white eyelid. They appear frenzied as they dive into water, sometimes at near freezing temperatures, and use their wings to propel them underwater. They walk, swim and dive underwater. Their main foods are aquatic insects which they find under rocks and in crevices. Although insects are captured underwater, the bird brings them to the surface to eat.

Uniquely adapted to this special environment, dippers share many traits of waterfowl, including exceptionally dense feathering that allows them to remain dry and buoyant in the water. When swimming on the surface, they paddle rapidly with feet and wings. One account reports a dipper being swept over the brink of a waterfall in Yosemite. That bird emerged unscathed and flying at the base of the waterfall, only to return to the exact same spot where it had been previously foraging. Like ducks, dippers molt all their flight feathers at once, and are flightless from four days to two weeks. During this time, they are extremely secretive, taking short fluttering leaps and escaping predation by swimming above or below the water’s surface and hiding under logjams, tangled vegetation, or overhanging banks.

In fact, the very presence of an American Dipper in a particular watershed is an indicator of ecological stream health. As a free-flowing river, the Jemez meets the needs of this species, which requires unpolluted waters, free from agricultural discharges, and without clear-cut deforestation that opens habitat, increases water temperatures, and alters the entire aquatic food web. Upon removal of forest, soil becomes compacted, and erosion, silting, and runoff are accelerated.

Healthy dipper populations on upland rivers througout the world indicate healthy river ecosystems. Along the Jemez River, I’ve observed dippers at East Fork, Jemez Falls, and Soda Dam but only during the times of year when the river receives reduced recreational use. During the times when the river receives heavy use, the birds inhabit those areas that are less accessible to humans. At any rate, each dipper observation, regardless of the time of year, tells us that we are doing something right in managing the Jemez watershed.

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