Yellow-billed Cuckoo
Yellow-billed Cuckoos are renowned as consumers of hairy and spiny caterpillars. They have been observed scraping off the hairs by shifting their mandibles back and forth over a caterpillar held crosswise in the bill.

The Yellow-billed Cuckoo once ranged throughout most of the United States, southern Canada, and Mexico, but has experienced severe population declines, particularly west of the Rocky Mountains. By the 1920s, the Yellow-billed Cuckoo had disappeared from its former range in British Columbia, and by the 1950s the species no longer bred in the northwestern United States, including northern California. Today, only small remnant populations persist in the West, in a few scattered locations in southern California, Arizona and New Mexico.
Yellow-billed Cuckoo Range Map

The cause of this disastrous decline was habitat loss. In the West, Yellow-billed Cuckoos are dependent on riparian forests, particularly cottonwood and willow. The majority of these habitats have been destroyed by logging, overgrazing, dams and water diversions. In the East, suitable habitat is more dispersed and the Yellow-billed Cuckoo's decline has been less drastic. However, Breeding Bird Surveys show large and significant declines in nearly half of the states with sufficient data to determine a trend for the years 1966 to 1999.

Local populations of Yellow-billed Cuckoos increase with outbreaks of tent caterpillars, common prey. Yellow-billed Cuckoos also eat other insects, small vertebrates, bird eggs, and occasional fruit such as grapes, mulberries and elderberries.

Nests are loosely constructed twig platforms lined with grass, leaves, pine needles, flowers and moss. They are shallow and so flimsy that eggs are sometimes lost. The parents arrive on the breeding grounds relatively late in the spring. The nesting season is greatly accelerated. The female lays three to five eggs. After a short incubation period of nine to eleven days, the young hatch. They develop rapidly. At one week, they are able to leave the nest to climb about on branches. In three weeks they can fly. Yellow-billed Cuckoos depart early in the fall for wintering grounds as far south as Argentina.

Yellow-billed Cuckoos often perch quietly motionless for extended periods of time while hidden in foliage. They may often be overlooked but for their songs. The characteristic song consists of a long series of guttural wooden-sounding notes that begins rapidly but decreases in speed, as "kuk, kuk, kuk, kuk, cyow, cyow, cyow, cowp, cowp, cowp." Another call is a soft, mellow, slowly repeated, "ough, ough, ough." In folklore, the song of the Yellow-billed Cuckoo has been said to presage a rain. The species is sometimes called the "rain crow," along with the similar-sounding Black-billed Cuckoo.

Description: Cuckoos are slender birds with down-curved pointed bills. The bill is mostly yellow with a dark culmen. Juveniles in their first summer may lack yellow bills. Yellow-billed Cuckoos are dark on the upper side, with a strongly contrasting white throat, breast and belly. The dark eye is surrounded by a yellow ring, and a slight black mask.Their flight is smooth and direct, with the long tail streaming straight out behind. The primaries of the wings show rufous in flight, a field mark useful to distinguish the Yellow-billed from the similar Black-billed cuckoo (C. erythropthalmus) and the Mangrove Cuckoo (C. minor) of southern Florida. Yellow-billed Cuckoos and Mangrove Cuckoos both have large white spots on the underside of the tail, unlike Black-billed Cuckoos, which have small distinct white spots. However, the Mangrove Cuckoo is easily distinguished by the buffy wash on its lower breast and belly, a more distinctive dark mask, and less yellow on the bill. Black-billed Cuckoos have red orbital rings, dark bills and no mask.


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