- 11–12.2 in
- 13.4–15.7 in
- 1.4–2.3 oz
- Coulicou à bec noir (French)
- Cuclillo piquinegre, Cuclillo pico negro (Spanish)
- Cuckoos eat many spiny caterpillars and the spines stick in the lining of the stomach. The stomach lining is periodically shed to remove the spines.
- The apparent tendency to call more frequently before rain explains why both Black-billed and Yellow-billed cuckoos are called "Rain Crows."
- Like its Old World relatives, the Black-billed Cuckoo is known occasionally to lay eggs in the nest of other bird species.
- The time from egg laying to young leaving the nest is, at 17 days, among the shortest for any bird. Despite this speed, most pairs raise only one brood a year.
- The oldest known Black-billed Cuckoo was at least 4 years old; it was banded in Ontario and recovered in Connecticut.
Black-billed Cuckoos are birds of woodlands and thickets, including aspen, poplar, birch, sugar maple, hickory, hawthorn, and willow. They tend to occur in more extensive tracts of woods than the Yellow-billed Cuckoo and are more likely to be found in deciduous than coniferous woods. On their South American wintering grounds they live in forest, woodlands, and scrub.
Black-billed Cuckoos eat large insects such as caterpillars, katydids, cicadas, and grasshoppers. They seem to have a particular appetite for large caterpillars—collected individuals have often been found with more than 100 in their stomach at once. Along with Yellow-billed Cuckoo, this is one of only two species found to be more numerous during periodic cicada emergences in a recent analysis. Black-billed Cuckoos occasionally eat eggs of other birds. On their wintering grounds they also eat fruit and seeds.
- Clutch Size
- 2–5 eggs
- Number of Broods
- 1-2 broods
- Egg Length
- 0.9–1.3 in
- Egg Width
- 0.7–0.9 in
- Incubation Period
- 10–11 days
- Nestling Period
- 6–7 days
- Egg Description
- Greenish-blue, unmarked.
- Condition at Hatching
- Helpless, but alert and active within minutes of hatching. Shiny black skin, no down.
Both adults help build the nest, with the female laying eggs in it before it's completed. The nest is flimsy—a shallow cup made of twigs and grasses and lined with dead or green leaves, pine needles, stalks, plant fibers, rootlets, mosses, and spider webs. The finished nest is about 6 inches across, with an inner cup that is 3 inches across and less than an inch deep.
Black-billed Cuckoos hide their nests among leaves or tangles in deciduous trees, shrubs, or brambles (occasionally coniferous trees such as hemlock). Nests are usually less than 7 feet off the ground but can be up to 50 feet high.
Black-billed Cuckoos catch prey by sitting motionless for long periods, then running or hopping out at prey. They often shake and hammer caterpillars against a branch to remove their spines before swallowing. Black-billed Cuckoos occasionally lay eggs in nests of other birds, though they do this far less often than the European cuckoo or the Brown-headed Cowbird. Among their hosts are other Black-billed Cuckoos, Yellow-billed Cuckoos, Chipping Sparrows, American Robins, Gray Catbirds, Wood Thrushes, and six other species. Young leave the nest at 6-7 days old, about two weeks before they will be able to fly. Waits motionless for long periods, watching for prey to move.
Black-billed Cuckoo populations have been declining since 1966 according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 870,000, with 53% breeding in Canada, 47% spending part of the year in the U.S., and 100% passing through Mexico to their wintering grounds in South America. They rate a 13 out of 20 on the Continental Concern Score, and they are on the 2014 State of the Birds Watch List, which lists bird species that are at risk of becoming threatened or endangered without conservation action. Black-billed Cuckoo is also listed as a High Priority concern on Audubon Watch Lists. Because caterpillars are a main prey they can be susceptible to pesticide use. Black-billed Cuckoos are also frequently felled by collisions with TV towers, tall buildings, and other structures during migration. Their populations fluctuate considerably from year to year as the birds move from place to place following outbreaks of prey. This variability makes it difficult to determine whether their overall numbers show a trend upward or downward. However, regional (statewide) estimates suggest that populations are declining.