Black-billed Cuckoos are birds of woodlands and thickets, including aspen, poplar, birch, sugar maple, hickory, hawthorn, and willow. They tend to occur more frequently in larger and denser woodlands than the Yellow-billed Cuckoo. On their wintering grounds, they live in forest, woodlands, and scrub.Back to top
Black-billed Cuckoos eat large insects such as caterpillars, katydids, cicadas, and grasshoppers. They seem to have a particular appetite for caterpillars such as fall webworms, tent caterpillars, and gypsy moths. Individuals have often been found with more than 100 caterpillars in their stomach at once. On their wintering grounds they also eat fruit and seeds.Back to top
Black-billed Cuckoos hide their nests among leaves or tangles in deciduous trees, shrubs, or brambles (occasionally evergreen trees such as hemlock). Nests are usually less than 7 feet above the ground, but can be up to 50 feet high.
Both adults help build the nest, but the female often lays eggs in the nest 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 spiderwebs. The finished nest is about 6 inches across and less than an inch deep.
|Clutch Size:||2-5 eggs|
|Number of Broods:||1-2 broods|
|Egg Length:||0.9-1.3 in (2.4-3.3 cm)|
|Egg Width:||0.7-0.9 in (1.8-2.4 cm)|
|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.|
Black-billed Cuckoos move slyly through thickets and often don't budge at all. When they do fly they have a graceful flight, flying on long and pointed wings. They catch prey by sitting motionless for long periods, then running or hopping out to grab caterpillars. They often shake and hammer caterpillars against a branch to remove their spines before swallowing, but sometimes they swallow them spines and all. They tend to forage lower to the ground than Yellow-billed Cuckoos, occasionally even foraging on the ground. Males court females with food prior to mating and form monogamous bonds for the breeding season. Black-billed Cuckoos occasionally lay eggs in nests of other birds, though they do this far less often than the Common Cuckoo (of Europe) 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. Males and females incubate the eggs continuously until they hatch. Young leave the nest at 6–7 days old, about two weeks before they can fly.Back to top
Black-billed Cuckoos are uncommon, and their populations declined over 2% per year for a cumulative decline of approximately 67% between 1970 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 880,000 and rates them 13 out of 20 on the Continental Concern Score, indicating a species of high conservation concern. They have included Black-billed Cuckoo on the Yellow Watch List-D for species with population declines that have moderate to high threats. If current rates of decline continue, Black-billed Cuckoos will lose half of their remaining population by 2037. Black-billed Cuckoo numbers fluctuate annually with caterpillar and cicada outbreaks, but generally, the species appears to be declining across its range. Increases in pesticide use likely contribute to population declines in both caterpillars and cuckoos. Habitat degradation and loss on both the breeding and wintering grounds may also be contributing to population declines.Back to top
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