Dippers are small songbirds uniquely adapted to feeding under water. There are five species of dippers worldwide, but only one—the American dipper (Cinclus mexicanus)—occurs in North America. This species is a permanent resident throughout most of Alaska. The common name “dipper” comes from this bird's habit of bending its legs so its entire body moves up and down in a dipping motion. Dipping takes place most frequently when the birds are closely approached or disturbed; they rarely dip when feeding or resting. Dippers are also called “water ouzels,” and their Eskimo name, anaruk kiviruk, translates as “old woman sunk.”

General description: The American dipper is a stocky, solid gray bird, about 7½ inches long (19 cm), with a short tail. Juveniles and adults of both sexes are very similar. Although they have no webbing between their toes, dippers can swim across water by paddling with their legs and feet.

Dippers can dive and propel themselves under the water with swimming motions of their wings. In shallow water, they walk along the bottom of streams by grasping stones with their elongated toes. These birds use their wings to help them stay submerged.

Dippers are adapted to dive underwater. They have nasal flaps to prevent water from entering the nostrils, large urpygial (preen) glands from which they obtain oil for waterproofing their feathers, muscular modifications to help them swim with their wings, and probably the ability to see as well underwater as above. They also can decrease the blood supply to non-vital tissues and organs during diving and can store more oxygen in their blood than most non-diving birds.

In addition, dippers are well insulated to withstand icy streams and Alaska winters. Their plumage is unusually dense, and they have a greater number of outer feathers covering their heads, necks, and bodies than do most other perching birds of similar size. Of greatest importance, however, is the very heavy coat of down between the rows of a dipper's feathers; it is similar to that of ducks and other waterfowl. This down is excellent insulation and enables these birds to maintain, with less than a three-fold increase in metabolism, normal body temperatures when air temperatures are as low as 40 degrees below zero.

Habitat requirements: The American dipper spends almost all its life along small, clear streams from which it obtains its major food: aquatic insects. Clean streams and protected nesting sites are probably the two most important requirements for maintaining populations of the American dipper. Unpolluted streams are important for the production of the dippers' food, and good water clarity is needed so they can see their prey.

Life history: Little is known about this bird in Alaska, hence most information comes from studies done elsewhere.

The nests of dippers are rather globular structures about a foot in diameter. They are composed of an outer shell of moss and small amounts of interwoven grass and roots, with an inner, cup-like lining of dry, coarse grass. Usually dippers' nests are placed where water spray keeps the outer structures green and moist; the coarse inner grass resists moisture, so the insides remain relatively dry. Entrance to the nest is through a small hole in the side. The nests are well constructed, and some are used year after year. In Europe, continued use of one dippers' nest dated back more than 100 years.

Dippers generally lay their eggs during the period from April through June, but later dates are no doubt the rule further north or at higher elevations. On the average, dippers lay four eggs which are incubated 16 to 18 days. After hatching, the young birds spend about 24 days in the nest. This amount of time is about twice as long as that of birds using open nests. Dippers probably need more time to develop behaviorally and physically to meet the demands of their aquatic environment.

Many American dippers spend their lives in one watershed. Most movements are from spring/summer nesting areas, which may be far upstream, to winter feeding areas in the ice-free, lower portions of streams. In winter, the birds may also forage for food in the intertidal portions of streams of along saltwater beaches. On Alaska's North Slope, dippers inhabit the ice-free spring areas in winter. The American dipper is highly territorial and may defend more than a half mile of stream in summer and as much as 1,000 feet of stream in winter. Like other songbirds, the dipper declares or “stakes out” its territory by singing. Territorial singing during winter, however, is quite unusual for any songbird. The dipper's song is very melodious and sounds like a long rendition of some of the best notes of thrushes and wrens. Both sexes may be heard singing during all months of the year except immediately after the young have left the nest.

Food habits: Dippers feed almost exclusively underwater on larval forms of aquatic insects. Studies indicate insects of the orders Plecoptera (stoneflies), Ephemeroptera (mayflies), and Trichoptera (caddisflies) are the most often eaten. To a much lesser extent, dippers will feed on small fish and fish eggs. In addition, during times of peak insect emergence, dippers may be seen flying out, in flycatcher fashion, on short round-trips after insects or skimming the newly emerged insects from the water surface.

Predators: The sharp-shinned hawk, mink, marten, weasel, wolverine, and large fish have been reported as preying on or pursuing dippers; however, dippers are not readily preyed upon. Their solid gray plumage camouflages them as they run across boulders along streams. Their inaccessible nesting sites, ability to dive under water, solitary habits, and their habit of flattening out and remaining motionless on the surface of the water when danger approaches also make them difficult to see or catch.

Management considerations: Most streams have very few adequate nesting sites for dippers. Identification and protection of these sites may be crucial to maintaining dippers in a particular watershed.

Text: Robert H. Armstrong and Rita M. O'Clair
Illustration: Katherine Hocker
Revised and reprinted 1994