Plaintive Cuckoo (Cacomantis merulinus) – A Comprehensive Study

Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Cuculiformes
• Family: Cuculidae
• Genus: Cacomantis
• Species: Cacomantis merulinus

The Plaintive Cuckoo (Cacomantis merulinus) is a small, secretive cuckoo species widely found across Asia, including the Indian subcontinent, Southeast Asia, and parts of China. This bird is known for its melancholic, high-pitched call, which often signals the arrival of the monsoon season.

Morphology & Physical Description

• Size: 21–23 cm in length
• Wingspan: 27–33 cm
• Weight: Around 30–40 grams
• Plumage:
  • Adults: Upperparts are greyish-brown to olive-brown, with a slightly paler underside.
  • Juveniles: More rufous with barring on the underparts and wings, resembling other cuckoo species.
• Head Features: A relatively small head with a slender, slightly curved beak.
• Beak: Dark grey to black, adapted for insectivorous feeding.
• Eyes: Dark and round, enhancing night and low-light visibility.
• Tail: Long and graduated, often held slightly downward.

Habitat & Distribution

The Plaintive Cuckoo is a versatile species, found in diverse habitats including:

• Mangrove forests, wetlands, and coastal thickets
• Secondary forests and agricultural landscapes
• Shrublands, grasslands, and lightly wooded areas
• Urban parks and gardens with dense vegetation

Presence in the Sundarban

The Sundarban, being a vast mangrove ecosystem, provides an ideal habitat for the Plaintive Cuckoo. It is commonly observed in:

• Dense mangrove vegetation along riverbanks
• Canopy-rich areas where it can hide while calling
• Shrubby islands and estuarine fringes
• Open scrublands at the Sundarban’s periphery

While not as commonly recorded as some other cuckoo species, the Plaintive Cuckoo thrives in the Sundarban due to its preference for dense, wetland-adjacent vegetation. Its presence is seasonal, with higher activity during the monsoon and early winter months.

Feeding Behavior & Diet

The Plaintive Cuckoo is an insectivorous bird, primarily feeding on:

• Caterpillars and larvae (including hairy caterpillars that other birds avoid)
• Beetles, grasshoppers, and other soft-bodied insects
• Small spiders and invertebrates
• Occasionally, it consumes berries and small fruits.

Foraging Strategy

• Perches silently on low branches before making a quick sally to catch prey.
• Hunts alone or in pairs, rarely seen in flocks.
• Often follows mixed-species flocks, benefiting from insect disturbances.

Breeding & Nesting

• Breeding Season: Primarily during the monsoon and early winter (June–November).
• Nesting Behavior: The Plaintive Cuckoo is a brood parasite, meaning it lays eggs in the nests of warblers, prinias, and tailorbirds, relying on them for incubation and chick-rearing.
• Egg Mimicry: Its eggs resemble those of host species, reducing the chances of rejection.
• Hatchlings: The young cuckoo often pushes out host eggs or chicks, ensuring exclusive parental care from the unsuspecting foster parents.

Vocalization & Communication

The Plaintive Cuckoo is named after its distinctive, sorrowful calls, which are:

• A repeated “pee-pee-pee” or “piu-piu-piu” sound
• Often delivered from a hidden perch in dense foliage
• More frequent during breeding season and at dawn or dusk

This call is one of the most recognizable bird sounds in its habitat and is often used to locate individuals despite their cryptic nature.

Special Adaptations

1. Brood Parasitism: Instead of building nests, it relies on host species to raise its young.
2. Egg Camouflage: Lays eggs that closely resemble host eggs, increasing survival chances.
3. Stealthy Movement: Prefers dense, concealed environments, avoiding predators.
4. Highly Adaptable: Can thrive in both urban and wild habitats, making it resilient to habitat changes.

Threats & Conservation Status

• Habitat Destruction: Mangrove deforestation and urban expansion threaten its breeding and feeding grounds.
• Climate Change: Rising sea levels and erratic weather patterns could impact its seasonal movement.
• Pesticide Use: Reduces insect populations, its primary food source.

IUCN Status: Least Concern (LC)

The Plaintive Cuckoo has a wide range and stable population, though localized threats could impact specific regions like the Sundarban. Conservation efforts should focus on protecting its wetland and mangrove habitats.

Conclusion

The Plaintive Cuckoo (Cacomantis merulinus) is a fascinating and elusive bird, playing a vital role in the Sundarban’s ecosystem as a brood parasite and insect controller. Its melancholic calls and secretive behavior make it a unique species, whose presence in the Sundarban adds to the region’s rich avian diversity. Ensuring the conservation of mangrove forests will help sustain this species in its natural habitat for generations to come.