Joy-bird.

Visualize a crystalline mountain stream tumbling down a forested, rock-strewn, western canyon. Then complete the picture with just the right touch: a small gray bird bobbing up and down on a rock.

You may have seen this remarkable creature but then forgotten since it is not brightly colored. This small (seven-to 8 1/2-inch), drab bird was a favorite of John Muir, the famous naturalist and writer. In his 1894 book, The Mountains of California; an entire chapter is devoted to "...the mountain stream's own darling, the humming-bird of blooming waters, loving rocky ripple-slopes and sheets of foam as a bee loves flowers..."

The American dipper, called the water ouzel in England, is indeed singular: It is America's only aquatic songbird, at home darting about in the air or walking on the bottom of a frothy stream looking for food.

Of the five members of the Cinclidae family around the world, the American dipper (Cinclus mexicanus) is the only one in North America. It can be found on rapidly flowing streams in areas of coniferous forest from Alaska to Mexico and from the Rocky Mountains to the Pacific Coast. During the winter it generally moves downstream to areas of open water and is considered to be nonmigratory. However, in southwestern states such as Arizona, dippers have been found in isolated "sky forests" surrounded by desert. They live there throughout the winter, then mysteriously disappear during the hot, dry months of summer.

It's fascinating to watch the dipper search for shallow-water insects as it scurries about in the riffles, submerging its head to look under rocks for food. Fishermen are often startled to see the dipper dive off a streamside rock and disappear underwater. It can remain there for as long as 30 seconds, and sometimes uses its wings to fly down to the stream bed, as deep as 30 feet, where it walks about looking for insects.

The dipper is specially equipped for underwater work with long toes to grasp the slick rocks, a nictating membrane (something like avian goggles) over its eyes, a movable flap to seal its nose, and a layer of down for insulation in the cold streams.

An oil gland 10 times larger than that of other songbirds waterproofs its feathers. The bird's primary food is the larval forms of flying stream insects - caddisfly and stonefly nymphs make up over 50 percent of its food.

The dipper is not partial to secluded stream settings; it is not shy and can be spotted near highway bridges and roads. When searching for dippers, look for these characteristics: The bird's flight is distinctive - its wingbeat is rapid, and generally it flies short distances and only a few inches to a few feet above the water. When on the ground, the dipper perches on a partly submerged rock or near-vertical rock face at streamside. It is seldom seen in trees or on dirt or sand stream banks.

When standing, the bird "dips" up and down at about 40 bows per minute. This motion, source of the name, is often what catches an observer's eye.

Also, use your ears! When trout fishing, I often first notice the dipper from the whir of its wings or its cheerful call. This delightful bird sings year-round with a loud musical dzeet or bzeet, which may be a single call or rapidly repeated.

A pair of dippers may make their home in the same nest year after year. The nests are circular, about basketball size, with a small entrance near the bottom. Males and females together form a nest of wet streamside materials, mostly moss and underwater weeds. Nests are difficult to find because they blend into the background and are often located in dark, damp places. Some favorite nesting places are above streams on vertical rock faces, below bridges, in dark holes between large rocks, and even behind waterfalls.

I have also found dipper nests totally exposed on top of midstream boulders. Four years ago I found one in Colorado's Frying Pan River. The nest was on a heavily fished "catch-and-release" trout stream where fishermen would wade close to it every day. The dippers, however, seemed to ignore the intruders and went on about their business, successfully raising a brood.

I returned to the Frying Pan this year, hoping to catch some trout and photograph the birds again. I caught some nice fish but was disappointed to find that the rock was not crowned with a dipper's nest. Fishing the boulder at sunrise on the second day, I was surprised to see dippers flying back and forth to the rock. Looking closer, I saw that the dippers were just beginning to build a nest, scurrying back and forth with wet material.

Although both of my visits were at the end of May, the dippers' activities differed each time. On the first visit, the year before, the birds had been feeding their young, but this year they were just beginning their nest. According to a Colorado Division of Wildlife officer, the dippers may have lost their nest to predation or a wind gust and perhaps were starting over.

The dipper's breeding cycle starts in late February or March. An old nest is repaired or a new one is made during March, April, or May. A clutch of three or four eggs is laid during this time, depending on the weather. The eggs hatch in 16 days, and then both parents search frantically for food the next 24 days, during which fledging, the growing of feathers, occurs. Since the nests are generally right above the water, the fledglings are immediately swimming and searching for food.

I had the pleasure of observing this fledging process. When I found the nest on the Dolores River in southwestern Colorado, I saw the parents feeding four chicks there. The next day, I noted that only three chicks were in the nest and one was on the rocks below. As I watched, two chicks dropped out of the nest, directly into the water. The force of the eight-foot fall pushed them under, but they popped to the surface like corks and swam to the banks as if they had been doing that for days. The parents returned with food and fed the chicks on the rocks.

The parents continue to provide food for the fledglings for a week or two, until the young ones are able to provide for themselves. By the next breeding season, the young will have been forced out of the breeding birds' territory (about a half mile of stream for each pair) and will have to find space elsewhere.

Dippers are full of surprises. I was recently watching a pair bring food to their nest when I saw one trying to feed the other, even though the other already had a nymph in its bill. This feeding attempt seemed to annoy the mate. Researchers believe the first stage of breeding behavior includes ritual feeding of the female by the male. I guess the male I was watching was so overworked he thought it was the beginning of the breeding season again. However, he did a good job of providing nymphs and grubs to his brood.

The pleasure of watching dippers is enhanced by their pristine environment. The dipper may be called the canary of the waterways - an indicator of a river's health. It thrives only where water quality is high enough to support the bird's food sources. Water insects are among the first life to disappear as a result of stream pollution.

When in the mountains, take time to appreciate the joy bird of the forests. As Muir wrote, "Find a fall, cascade or rushing rapid on a clear stream . . .there you will surely find its complementary Ouzel, flitting about in the spray, diving in foaming eddies, whirling like a leaf among beaten-foam bells."

Robert Barber writes about and photographs nature and wildlife from his home in Arvada, Colorado.