The yellow-billed cuckoo (Coccyzus americanus) is a neotropical cuckoo bird that breeds in North America and winters in South America. It gets its name from its yellow lower mandible. The yellow-billed cuckoo plays several important roles in its ecosystem:
Diet and Predation
The yellow-billed cuckoo is an omnivorous bird that feeds on insects, fruits, seeds and small vertebrates. Its diet consists predominantly of caterpillars, including tent caterpillars, webworms and larvae of butterflies and moths. It also eats beetles, grasshoppers, cicadas, spiders, snails, lizards, frogs and eggs.
The cuckoo is an important predator of many insect pests in North America, helping to control their populations. For example, outbreaks of forest tent caterpillars in the eastern United States are associated with low cuckoo numbers, indicating the significance of the cuckoo in suppressing caterpillar populations.
Seed Dispersal
Fruits and berries make up an important part of the yellow-billed cuckoo’s diet. As the bird feeds, it swallows seeds that pass through its digestive system and are later excreted whole. This facilitates seed dispersal for many plant species that the cuckoo feeds on. Plants whose seeds are spread by the cuckoo include poison ivy, dogwood, blackberry, sumac and elderberry.
By dispersing seeds away from the parent plant, the cuckoo helps maintain genetic diversity and spread vegetation to new areas. This seed dispersal role makes the yellow-billed cuckoo an important facilitator of forest regeneration.
Pollination
While feeding on nectar, the yellow-billed cuckoo also transfers pollen between flowers, serving as an occasional pollinator for some plant species. For example, the cuckoo has been observed visiting the flowers of the passionflower vine, likely resulting in pollination.
Influence on Host Birds
The yellow-billed cuckoo is a brood parasite, laying its eggs in the nests of other bird species to be raised by those host birds. Its common hosts include the American robin, gray catbird, wood thrush and red-eyed vireo.
Parasitism by the cuckoo influences breeding behavior and nesting success of the host species. Hosts may reject cuckoo eggs or abandon parasitized nests. Raising cuckoo chicks, which often outcompete host chicks, represents a reproductive cost for hosts. These effects exert evolutionary pressure on host species.
Range and Habitat
The breeding range of the yellow-billed cuckoo extends across much of the continental United States (except for the northwest) and into southern Canada. Its wintering range spans South America east of the Andes, including the Amazon basin.
The cuckoo inhabits a variety of wooded habitats during breeding, including open woodlands, parks, thickets, overgrown orchards and dense scrub. It tends to avoid unbroken expanses of forest. Nesting frequently occurs along riparian corridors. Habitat loss is a major threat to the yellow-billed cuckoo.
On its South American wintering grounds, the cuckoo is found in forests and woodlands up to about 6,500 feet in elevation. Its winter habitat includes primary rainforests as well as wooded savannas and scrublands.
Migration
The yellow-billed cuckoo is one of the latest spring migrants of any North American bird, typically arriving on breeding grounds in June and July. It migrates relatively early in fall, departing breeding areas as early as late July and August.
During migration the cuckoo makes a transoceanic journey, flying nonstop over the Caribbean Sea and Gulf of Mexico between its North American and South American ranges. It travels alone rather than in flocks.
Breeding and Reproduction
The yellow-billed cuckoo breeds between May and September across North America. It builds a flimsy nest of sticks in the fork of a tree branch, laying 2-5 eggs that are incubated by the female for about 11 days.
Courtship
Male cuckoos attract females through distinctive “kowlp” calls. In courtship display, the male fluffs his feathers, raises his wings and tails and performs bowing motions while making rhythmic “kowlp-kowlp-kowlp” vocalizations. If receptive, the female responds with a “kowlp” call circling the male.
Parental Care
The female alone incubates the eggs and cares for hatchlings. The male may occasionally deliver food to the female on the nest. Both parents feed the young regurgitated insects and other prey. Fledglings leave the nest at 10-17 days old.
Brood Parasitism
Yellow-billed cuckoos frequently lay eggs in the nests of other species. The female may remove one host egg before laying. Cuckoo chicks often outcompete host young, sometimes ejecting them from the nest. Parasitized birds raise at most 2-3 cuckoos.
Population Status
Due to declines over the last few decades, the yellow-billed cuckoo is considered a threatened/endangered species in parts of the western United States. Causes of declines include habitat loss, pesticide use reducing prey, and climate change.
However, the cuckoo’s overall population remains relatively large at about 12 million individuals. Partners in Flight estimates a global breeding population of 28 million, with 79% living in the US and Canada. Its numbers qualify it as a species of least concern according to the IUCN Red List.
Threats
– Habitat loss, especially along riparian areas. For example, 95% of California’s Central Valley riparian forests are gone.
– Heavy pesticide use reduces insect prey populations.
– Conversion of native forests to plantations in South America.
– Climate change may increase drought stress and cause breeding mismatches.
Conservation
– Habitat protection and restoration, especially of riparian areas.
– Enforcement of the Migratory Bird Treaty Act provides some protections.
– Public education programs to limit pesticide use.
– International cooperation needed to protect South American habitat.
Key Facts
Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Cuculiformes
Family: Cuculidae
Genus: Coccyzus
Species: Coccyzus americanus
Identification
– Slim, long-tailed bird about 30 cm (12 in) in length.
– Grayish-brown upperparts and white underparts.
– Yellow lower mandible (bill) with black upper mandible.
– Prominent white spots on undertail coverts.
– Ruby-red eyes.
– Flamboyant courtship display.
– Distinctive “kowlp” and “kowp” calls.
Behavior
– Migrates late spring/early fall between North and South America.
– Forages alone for insects and other prey in open woodlands.
– Male attracts female through elaborate courtship ritual.
– Sometimes practices brood parasitism on other species.
Diet
– Feeds mainly on caterpillars and large insects.
– Also eats fruits, seeds, spiders, snails, lizards and frogs.
– Forages actively in trees and shrubs.
Reproduction
– Breeds May through September.
– Builds flimsy nest of sticks in tree fork.
– Lays 2-5 eggs incubated by female for 11 days.
– Young fledge nest at 10-17 days old.
Conclusion
The yellow-billed cuckoo fills several important ecological roles across its North and South American ranges. As an insectivore it controls pest populations, while also dispersing seeds and pollinating plants. Despite some declining populations in parts of western North America, the cuckoo remains common overall. Protecting its preferred breeding habitat of open woodlands and riparian areas will be key to conserving this unique migratory bird into the future.
