American dipper

Cinclus mexicanus

TAXONOMY

Cinclus mexicanus Swainson, 1827, Temescaltepic, Mexico. OTHER COMMON NAMES

English: Mexican dipper, water ouzel, waterthrush; French: Cincle d'Amérique, cincle américain; German: Grauwasseramsel; Spanish: Cinclo Norteamericano.

PHYSICAL CHARACTERISTICS

6-7 in (15-17.5 cm); weight, male 2.0-2.3 oz (57-66 g); female,

I.5-2.3 oz (43-65 g). Plumage overall dark gray, paler on chin.

DISTRIBUTION

Western North America from Alaska (north to the Arctic Circle) and east Aleutians, south through western Canada to Arizona and Colorado; numerous disjunct populations from Mexico through Central America to Panama.

HABITAT

Rushing mountain streams; in winter also the fringes of lakes and beaver ponds, sometimes sea-shores. Sea-level in north to

II,000 ft (3,500 m); in Costa Rica 2,600-8,200 ft (800-2,500 m).

BEHAVIOR

Very similar to Eurasian dipper; dives into and swims in fast-flowing water, usually to be seen perched on a mid-stream boulder or flying low above the water. Song is a medley of single notes, audible for long distances; call a sharp "dzik."

FEEDING ECOLOGY AND DIET

Most food is taken from boulders or stream-beds. Birds usually only remain submerged for 10 seconds or less. Prey almost en-

tirely aquatic invertebrates. Will occasionally fly-catch; has been seen to pick frozen insects off stream-side snowbanks and beach-hoppers out of cast-up seaweed.

REPRODUCTIVE BIOLOGY

Nest is a spherical or elliptical ball with a side entrance, the outer layer grass or moss, inside a woven cup of grass, leaves and bark, usually located near or above flowing water in rock crevices; also, increasingly, in artificial sites such as bridges or nest boxes. Both sexes build. Eggs white, in North America usually four or five, in Costa Rica two to four. Incubation by female alone, 14-17 days, young fed by both sexes, 24-26 days. Sometimes double-brooded. Usually monogamous; males may, rarely, be polygamous.

CONSERVATION STATUS

Not threatened. Frequently common in pristine habitat but susceptible to water pollution from activities such as mining. Some populations apparently augmented by provision of nest sites such as bridges or suitable nest boxes.

SIGNIFICANCE TO HUMANS

Occasionally accused of causing significant damage to fish hatcheries; otherwise no other direct economic significance. ♦

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