Adult The entire plumage is dark slaty-grey, with a faint (but usually distinct) brownish wash over the head; birds in fresh plumage in the fall often have narrow pale fringes on the feathers of the underparts. The eyelids are white and can be seen when the bird blinks. Structurally, this species is distinctive with its rotund, chunky body and short tail that is usually held cocked. The iris is dark, the short, stout, pointed bill is blackish, and the relatively long, strong legs and feet are pinkish.
Juvenile This plumage is held throughout the first summer, but is generally lost by September. Juveniles are similar to adults, but the throat is whitish and the underparts have extensive whitish fringes to the feathers (giving them a mottled appearance). In addition, there are often very fine whitish edges to feathers of the upperwing coverts, tertials, and uppertail coverts. Bare part colouration is similar to the adult, but the bill is paler and pinkish or brownish with a darker culmen and the legs and feet are paler and flesh-coloured.
This species is very distinctive in appearance, behaviour, voice, and habitat and should not present any identification issues.
The song (produced by both sexes) is loud, emphatic, and piercing. It is a prolonged, jumbled, complex series of high whistles, trills, and ringing notes with individual phrases usually repeated several times in succession: k-tee, k-tee, wij-ij-ij-ij, treeeoo, treeeoo, tsebrr, tsebrr, tsebrr… The call note is a high, buzzy, metallic dzeet or dzik that is often repeated 2-3 times in quick succession. All vocalizations possess a high-pitched, piercing, ringing quality that enables them to be heard above the sound of rushing water (audible for >100 m over the sound of rushing creeks and rivers, or up to 1.5 km over quiet waters).
Courtship Although singing (by both sexes) occurs throughout the year, true courtship and pair formation activities in the American Dipper occur very early, with the initial stages of courtship occurring in mid-winter (December). During these earliest stages, the male and female associate closely with each other but do not engage in any overt courtship displays. As the winter progresses and courtship intensifies, the male begins ‘courtship feeding’ in which he feeds the female who crouches and flutters her wings in a manner that is reminiscent of a fledgling. The male may also engage in a ‘strutting’ display in which he sings with his bill pointed straight up and wings drooped, strutting back and forth in front of the female for 20-30 seconds. The final stage of courtship, which occurs during later periods in the spring (March-April), is a ‘flight chase’ display in which the male pursues the rapidly-flying female, sometimes only a few centimeters behind her, in twisting and turning flights up and down the river; these chase flights can last as long as 10 minutes.
Nest Nest-building begins in very early spring (February-March). Both sexes usually contribute to building the nest, although in some cases only the female contributes. Due to the naturally limited number of potential nest sites, and the durability of the nest, re-use of old nests is common in this species. The nest is placed on a cliff ledge, upturned tree root, hollow log, midstream boulder, man-made structure (bridge, dam, culvert, etc.), behind a waterfall, or underneath an overhanging dirt bank, and is almost always located above water in a location that is inaccessible to predators. The nest is a large, bulky dome-like structure with a side entrance that faces the water, often with the canopy of the dome overhanging the entrance hole in order to prevent spray from wetting the inside of the nest. The outer dome is composed primarily of moss, with smaller amounts of dried grasses and leaves (rarely sticks and conifer boughs). The dome is 20-25 cm in diameter with an interior chamber of ~14 cm diameter and an entrance hole that ranges from 5-10 cm in diameter (larger towards the end of the nesting period). A cup nest 5-7.5 cm in diameter is located within the dome and is composed of woven dry grasses, leaves, and strips of bark. In rare cases, such as when it is built under the shelter of a close overhang or in a cavity, the nest may be open and without a domed roof.
Eggs A clutch of (3) 4-5 (6) eggs is laid between mid-March and mid-April and is incubated by the female for 13-17 days before hatching. A second clutch is rarely produced in June and hatches by early to mid-July. The smooth, glossy eggs are entirely white and are unmarked. Eggs are present in British Columbia between mid-March and mid-July. This species has not been recorded as a host for Brown-headed Cowbird parasitism.
Young The young are fully altricial upon hatching and are naked except for patches of sparse down on the head and upperparts. The skin is orange on the abdomen and pink on the back, the mouth is orange-yellow, and the gape flanges are yellow. As they grow, the nestlings become very noisy and can be heard as far as 10 m away from the nest, even over the sound of rushing water. Older nestlings often peer out of the nest in anticipation of the returning parent. Both parents tend to the young during their time in the nest, although only the female does the brooding (for the first 10 days). The young leave the nest at 24-26 days of age and remain with the parents for as little as 4 days or as much as 24 days before becoming independent. During this fledgling period the parents often divide the brood between them, with each parent attending to 1-2 of its young, and remain in separate portions of the territory. The fledglings are able to swim and dive before they are capable of flight. Nestlings and dependent fledglings are present in B.C. between mid-April to mid-August.
Source: Kingery (1996); Baicich and Harrison (1997); Campbell et al. (1997)
The foraging habits of the American Dipper are remarkable and are not matched by any other songbird in North America (and are matched only by the remaining 4 species of dipper elsewhere in the world). It is extremely closely tied to aquatic habitats, especially those that are turbulent, cold, and clear, and virtually never occurs in terrestrial habitats beyond the banks of these watercourses. It feeds primarily on aquatic insects and their larvae (caddisflies, dragonfly nymphs, stoneflies, etc.) but will also consume small fish, fish eggs, and flying insects. Most prey is captured within the water or at the surface by swimming or diving, and this is the only passerine that is adapted to feed aquatically in this way. Foraging birds rest on in-stream rocks or logs between foraging bouts, subsequently diving immediately into the water from this perch or swimming at the surface and scanning underwater for prey, which it then procures by diving underwater. It sometimes dives into the water directly from short flights. While underwater, the American Dipper gleans invertebrates from the surface of rocks and vegetation, or uses its short, stout bill to move debris to reach invertebrates that are hiding underneath. All prey is consumed above the surface of the water, so the bird must return to the surface after it has captured an organism. The bird generally remains under water for <15 seconds during dives, but dives of up to 30 seconds have been reported. When foraging above water, this species gleans or picks prey from the surface of rocks, woody debris, ice, or snow in a manner similar to a turnstone. It rarely captures flying insects by ‘flycatching’ from a perch on a rock or log. This species continually bobs, or ‘dips’, its body when perched above water.
Source: Kingery (1996)
This species is found only along rivers and rarely, if ever, strays beyond their banks, although some birds may forage along lakeshores near their breeding territory. It prefers clear, cold, high-velocity rivers and streams at all elevations, particularly where there is an abundance of emergent rocks and logs in and around the watercourse for perching. Smaller waterways (usually <15 m in width) are preferred during the breeding season, but larger, slower rivers are often inhabited during the winter, particularly in the northern and central interior where these are usually the only areas of open water that are available. Breeding birds are usually found in areas with rocky banks, cliffs, or other sturdy structures upon which to build their nest (bridges, etc.). Most foraging occurs in shallow water in areas with rapids and riffles, at the base of waterfalls, or (in the winter) at the edge of the ice along frozen northern rivers.
Resident throughout much of western North America, from northern Alaska and the Yukon south to the Mexican border and east to the Rocky Mountains. It is also resident in disjunct populations in mountainous areas of western Mexico and Central America, south to Panama.
Resident Uncommon to fairly common along the coast, including both Vancouver Island and the Queen Charlotte Islands, as well as throughout the interior east to the Rocky Mountains (where it can be locally common in some areas during the winter). It is rare to uncommon on the eastern slopes of the Rocky Mountains and its foothills in northeastern B.C., ranging farther downstream along the Peace River during the winter. During the breeding season, it is generally rare to uncommon at low elevations in central B.C. but becomes more common during the winter as birds leave the frozen mountain streams for the larger rivers in the valley bottoms; similar altitudinal movements occur widely throughout the range of this species in B.C. In addition, populations in northern portions of the interior may be at least partially migratory as there are few areas of suitable open water available in that region during the winter.
Source: Kingery (1996); Campbell et al. (1997)
Population and Conservation Status
Populations of American Dipper appear to be relatively large and stable, although populations elsewhere throughout its range (particularly in the Unites States, Mexico, and Central America) are naturally fragmented and may be susceptible to localized extinction events. This species is not recognized a conservation concern by either COSEWIC (Committee on the Status of Endangered Wildlife in Canada) or the B.C. CDC (Conservation Data Centre).
Five subspecies of the American Dipper are recognized, but only one of these (C.m.unicolor) is found with the Canadian and U.S. portion of the species’ range. Other subspecies of Mexico and Central America differ subtly in the tone of the plumage (e.g, slightly browner, darker, or paler than C.m.unicolor) but are otherwise very similar.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
27/06/2017 1:49:16 AM]
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