Green-billed Coucal

The Green-billed Coucal is easily identified by its distinctive green bill, which contrasts with its otherwise dark plumage. Adult coucals have a glossy black body with a purplish sheen, particularly noticeable when sunlight strikes their feathers. Their wings are a rich chestnut brown, providing a striking contrast to the darker body and tail. Juvenile coucals, on the other hand, exhibit more muted colors with a streaked brown appearance that helps them camouflage within the dense foliage. Unlike many bird species, there is no significant difference in plumage between male and female Green-billed Coucals. However, their large size and distinctive coloration make them hard to confuse with other birds in their habitat. In flight, the Green-billed Coucal displays broad, rounded wings and a long tail, which aids in maneuvering through the thick forest canopy. When perched, they often appear hunched, with their head and bill angled downward, a posture that is characteristic of the species. This perching behavior, combined with their unique vocalizations, makes them more detectable to an observant birder.

The diet of the Green-billed Coucal is diverse, comprising mainly large insects, small vertebrates, and occasionally fruits. It is an opportunistic feeder, adapting its diet based on the availability of food sources. During the wet season, when insect activity peaks, the coucal primarily consumes grasshoppers, crickets, and beetles. It also preys on small reptiles, amphibians, and even nestlings of other bird species. The bird employs a stealthy foraging technique, moving slowly and methodically through the underbrush to surprise its prey. Its strong bill allows it to tackle relatively large prey items, which it often beats against a branch to subdue before swallowing. The Green-billed Coucal's feeding schedule is largely diurnal, with peak activity occurring during the early morning and late afternoon hours. This schedule allows it to take advantage of the cooler parts of the day when prey is more active.

The Green-billed Coucal exhibits a solitary and secretive lifestyle, spending much of its time hidden in dense vegetation. It is a territorial bird, with pairs or individual birds maintaining and defending their territories against intruders. During the breeding season, the coucal becomes more vocal and can be heard calling throughout its range, especially at dawn and dusk. Courtship displays involve a series of low-pitched, booming calls, often accompanied by a display of plumage and tail feathers. Although primarily solitary, the coucal may occasionally form loose associations with other coucals in areas with high population densities. When threatened by predators, such as snakes or birds of prey, the Green-billed Coucal can emit loud alarm calls and frequently uses its agility to navigate through thick underbrush to escape. Its daily activity pattern involves periods of foraging interspersed with rest, typically in concealed perches within the forest.

The Green-billed Coucal constructs a large, domed nest, typically located in the dense undergrowth of forests. The nest is composed of twigs, leaves, and grasses, intricately woven together to create a sturdy structure that provides protection from predators and the elements. Nesting sites are generally chosen in areas with abundant cover, such as thickets or low-lying shrubs, to ensure concealment. The typical clutch size consists of two to three eggs, which are white and unmarked. Both parents participate in incubation, which lasts approximately 15 to 18 days. After hatching, the chicks remain in the nest for about three weeks before fledging. During this period, both parents are actively involved in feeding and caring for the young. The Green-billed Coucal usually raises one brood per year, although in favorable conditions, a second brood may be attempted.

The Green-billed Coucal's primary song is a series of deep, resonant booms that carry well through the dense forest. This song, often described as 'hoo-hoo-hoo,' serves as a territorial call and a means of communication between mates. Its rhythm is slow and deliberate, with each note lasting about a second. In addition to its song, the coucal produces a variety of call notes, including harsh, clucking sounds used in alarm situations. During the dawn chorus, the coucal's booming calls can be heard echoing through its range, often in response to other coucals. The sound of the Green-billed Coucal is distinctive and can be likened to the distant sound of a beating drum, offering an auditory clue to its presence even when it remains unseen.

• 1The Green-billed Coucal's call can be heard up to 2 kilometers away, making it a key auditory presence in its habitat.
• 2Unlike many cuckoo relatives, the Green-billed Coucal builds its own nest rather than laying eggs in the nests of other birds.
• 3This coucal's diet includes carrion, a trait that helps it play a role in nutrient cycling within its ecosystem.
• 4The Green-billed Coucal is endemic to Sri Lanka, highlighting the island's unique biodiversity.
• 5Despite being non-migratory, the Green-billed Coucal shows some seasonal movement within its range to adapt to rainfall patterns.
• 6Coucal chicks grow rapidly, fledging within three weeks, one of the shortest periods for birds of similar size.
• 7The bird's green bill is not only distinctive but also functional, aiding in the capture and handling of various prey.

The Green-billed Coucal is currently classified as Vulnerable on the IUCN Red List due to its restricted range and ongoing habitat loss. The primary threat to its population is deforestation, driven by agricultural expansion, logging, and human settlement. Conservation efforts focus on protecting the remaining forest habitats in Sri Lanka, such as the Sinharaja Forest Reserve, which is a UNESCO World Heritage Site. Historical population data suggests a decline in numbers, correlating with the reduction in forest cover over recent decades. Despite these challenges, initiatives to restore degraded habitats and establish protected areas offer hope for the long-term survival of the Green-billed Coucal. Continued monitoring and research are essential to understanding population trends and developing effective conservation strategies.