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"[H]is music is that of the streams refined and spiritualized. The deep booming notes of the falls are in it, the trills of the rapids, the gurgling of margin eddies, the low whispering of level reaches, and the sweet tinkle of separate drops oozing from the ends of mosses and falling into tranquil ponds." —John Muir, 1894 (1: 283).
John Muir's “Ouzel” or “Water Thrush” now bears the name American Dipper, a name that describes the most conspicuous habit of most species in the family Cinclidae: a repetitive up-and-down bobbing motion. Admirers of Muir's Ouzel have attributed to it a combination of factual and mythical characters. Muir declared “bird and stream...inseparable,” which is essentially true. Although dippers rarely stray from rushing streams, they do on occasion frequent lakes and seashores. They do not restrict themselves to mountains; some individuals nest along coastal streams from Alaska to California and on desert streams in the Grand Canyon and in Zion National Park.
The American Dipper chooses a nest site, invariably along a stream, that usually provides security from floods and predators. Availability of suitable streams and nest sites and territorial behavior where potential nest sites are close together appear to limit its populations. It eats an exclusively animal diet, composed almost entirely of aquatic insects, invertebrates and, where available, small fish and fish eggs.
This species' distinctive traits include frequent dipping, a blinking white eyelid, and vigorous feeding by jumping or diving into turbulent water even at ambient temperatures well below 0 °C. To persist in this demanding environment, the American Dipper has a low metabolic rate, extra oxygen-carrying capacity in its blood, and a thick coat of feathers. It aggressively defends territories in both summer and winter along streams.
Half a century after Muir's glowing accounts of the American Dipper in the Sierra Nevada, a number of researchers began to study its life history. Hann (2) studied nesting behavior on the East River in west-central Colorado (near Gothic, Gunnison County). In western Montana (Missoula County), Bakus (3, 4) studied breeding behavior, and population density; Mitchell (5) studied diet; and Sullivan (6) studied diet, molt, and adaptations to the aquatic environment. Ealey's (7) study on the Sheep River near Calgary, Alberta, reported on ecology and breeding behavior. In a 3-year study on Boulder Creek in north-central Colorado (Boulder County), Price researched population dynamics (8, 9). Working with dippers on the Logan River in northeastern Utah (Cache County), Fite (10) analyzed vocal behavior. Additional studies have addressed the species' physical adaptations (internal and external) to aquatic life (11, 12, 13, 14).
Recent studies in southern British Columbia have focused on altitudinal migration, life history, fledgling behavior, and toxicology (15, 16, 17, 18, 19, 20, 21, 22, 23, 24). In southeastern Alaska, Willson and Hocker (25, 26, 27, 28) studied breeding and wintering ecology, parental behavior, and factors limiting distribution and abundance. Lovett (29) studied their biology in the Black Hills of South Dakota. As North America's only truly aquatic passerine, the American Dipper combines some characteristics of passerines (melodious song and aggressive territoriality) with some of ducks (feeding, molt, and dense feathering). Most of the information in this account pertains to the subspecies C. m. unicolor, which resides in the United States and Canada; little has been published on the 4 subspecies found in Mexico and Central America (see Systematics: Subspecies).