Lesser Cuckoo (Cuculus poliocephalus) – A Detailed Study

Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Cuculiformes
• Family: Cuculidae
• Genus: Cuculus
• Species: Cuculus poliocephalus

The Lesser Cuckoo (Cuculus poliocephalus) is a migratory cuckoo species known for its distinctive calls and brood parasitism. This bird is often confused with other small cuckoos but can be distinguished by its size, plumage, and vocalizations.

Morphology & Physical Description

• Size: 24–27 cm in length
• Wingspan: Around 45 cm
• Weight: 40–60 grams
• Plumage:
  • Upperparts: Greyish-brown with a bluish tinge on the head.
  • Underparts: White with dark brown barring.
• Head Features: Slender greyish head with a slightly darker crown.
• Eyes: Bright yellow iris, which stands out against its dark head.
• Beak: Short, slightly curved, and blackish in color.
• Tail: Long and barred with white tips, aiding in maneuverability.
• Legs & Feet: Short, with a zygodactyl foot structure (two toes facing forward and two backward), useful for gripping branches.

Habitat & Distribution

The Lesser Cuckoo inhabits a variety of forested and semi-open environments, including:

• Tropical and subtropical forests
• Dense mangrove forests (including the Sundarban)
• Woodlands, scrublands, and foothills
• Himalayan foothills and Eastern Ghats during breeding seasons

Presence in the Sundarban

The Sundarban, with its extensive mangrove forests and estuarine ecosystems, provides an ideal habitat for the Lesser Cuckoo during its migratory phase.

• It is a summer visitor, typically arriving between April and September.
• Prefers mangrove canopies and riverine edges for foraging.
• Often heard more than seen, due to its cryptic behavior.
• Uses the dense mangroves and adjacent wetland vegetation for roosting and feeding.

Feeding Behavior & Diet

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

• Caterpillars, including hairy and toxic species that other birds avoid.
• Beetles, moths, grasshoppers, and other arthropods.
• Occasionally, it consumes small fruits and berries.

Foraging Strategy

• Prefers hunting among dense foliage, particularly in mangrove trees.
• Uses a “sit-and-wait” strategy, scanning for prey from a perch before making quick aerial sallies.
• Sometimes follows mixed-species flocks, especially during migration.

Breeding & Reproductive Behavior

The Lesser Cuckoo is an obligate brood parasite, meaning it lays its eggs in the nests of other bird species.

• Breeding Season: Varies by region but usually April–August.
• Host Birds:
  • Primarily small warblers and babblers, which incubate its eggs and raise its chicks.
  • In the Sundarban, potential host species include Common Iora, Jungle Babbler, and tailorbirds.
• Egg Mimicry:
  • The cuckoo’s eggs closely resemble those of its host species, reducing the chances of rejection.
• Chick Behavior:
  • Once hatched, the cuckoo chick often pushes out host eggs or chicks, ensuring it receives all parental care.

Vocalization & Communication

The Lesser Cuckoo is best identified by its distinctive and repetitive calls, which are most prominent during the breeding season.

• Main Call: A high-pitched “pee-pu pee-pu” or “kwee-wee-kwee” sound, repeated rhythmically.
• Alarm Call: A rapid “chirr-chirr-chirr” sound when disturbed.
• Territorial Calls: Males sing loudly to attract females and establish dominance.

Special Adaptations

1. Brood Parasitism: Allows it to focus on migration and feeding without parental responsibilities.
2. Egg Mimicry: Reduces rejection risk by host birds.
3. Silent Flight: Helps it approach host nests unnoticed.
4. Highly Cryptic Behavior: Stays hidden in foliage, reducing predation risk.
5. Specialized Diet: Can digest toxic caterpillars that other birds avoid.

Threats & Conservation Status

Though the Lesser Cuckoo is not globally threatened, it faces localized challenges, including:

• Deforestation & Habitat Loss:
  • Reduction in mangrove forests (like in the Sundarban) affects its seasonal presence.
• Climate Change & Weather Patterns:
  • Altered monsoon cycles impact insect populations, reducing food availability.
• Declining Host Bird Populations:
  • Loss of small warblers and babblers affects successful reproduction.
• Pesticide Use:
  • Decreases insect abundance, directly impacting its food source.

IUCN Status: Least Concern (LC)

The Lesser Cuckoo has a stable global population, but its dependence on intact forest and mangrove ecosystems means that conservation efforts in regions like the Sundarban are crucial for maintaining its migratory population.

Conclusion

The Lesser Cuckoo (Cuculus poliocephalus) is a fascinating migratory cuckoo, known for its brood parasitism, distinctive calls, and reliance on dense forests like the Sundarban for survival. Although it is not a resident species, its seasonal presence highlights the importance of preserving mangrove habitats, ensuring a safe passage for migratory birds that depend on this delicate ecosystem.