Cinclidae (Dippers)
American Dipper,Cinclus mexicanus. (Fig. 11.35) Male length 7 in (17.5 cm), female length 6 3/4 in (17 cm); male weight 2 1/8 oz (60 g), female weight 1 3/4 oz (49 g). Small numbers of this species occur year-round in the deep, wet canyons of the White Mountains, up to elevations of approximately 10,000 ft (3,050 m).
The American Dipper occurs only along permanently flowing streams characterized by cool, swift, clear water. Aquatic insect larvae compose the bulk of their diet, but small fish and other invertebrates are occasionally eaten. Dippers get most of their prey directly from the fast-moving waters. They also flycatch and pick insect larvae from streamside rocks. The ability of dippers to forage in mountain streams is truly remarkable. With their strong feet they grasp the rubble on the bottom and wade
Figure 11.35
American Dipper.
underwater in search of food; in deeper, faster water, they typically use their wings while diving and swimming. The American Dipper usually stands on emerged rocks at the water's edge while foraging. Flight between such perches is rapid and low over the water. This species also breeds in the dampness of the stream environment. Preferred nest substrates are overhanging cliff ledges in areas protected from predators and inclement weather but exposed to water spray. Large rocks, tree roots, and undercut banks are commonly used. The mossy covering of the nest is moist and springy. Birds tend to breed in early spring, an adaptation that allows them to take advantage of an ample insect supply before late spring runoff decreases the availability of food. References: Morse (1979), Price and Bock (1983).