Sumatran Ground Cuckoo: One of the Least-Known Birds Alive

A ghost of Sumatran forests

The Sumatran Ground Cuckoo (Carpococcyx viridis) is a large, long-legged ground-dwelling cuckoo endemic to the lowland and hill forests of western Sumatra. Adults are around 55 cm long, with iridescent green upperparts, a heavy dark bill, and bare bluish-purple skin around the eye.

For most of the twentieth century, it was one of the least-known birds in the world. Until 1997 there were essentially no field records at all.

The 1997 camera-trap rediscovery

The species was described from specimens in 1879, then almost forgotten. In 1997, a live bird was accidentally caught in a snare in Bengkulu Province and briefly held before being released, confirming the species still existed.

In 2006, mammal researchers running camera traps in Kerinci Seblat National Park captured the first-ever photographs of a Sumatran Ground Cuckoo in the wild. Since then, further camera-trap detections have expanded the known range slightly, but the species remains extraordinarily hard to observe directly.

What little we know

Field observations are so few that basic biology remains speculative. The bird is thought to walk quietly through dense understorey, hunting large insects, small reptiles, amphibians and possibly small mammals. Its call, when finally recorded, turned out to be a series of hoarse notes given at dawn.

It appears to be closely related to the Bornean Ground Cuckoo (Carpococcyx radiatus) and was formerly treated as a subspecies of it. Genetic work supported elevation to full species status.

Where recent records have come from

Recent detections cluster in Kerinci Seblat and Bukit Barisan Selatan national parks in western Sumatra, mostly below 1,500 metres elevation. Additional records suggest the species persists at very low density across a broader arc of remaining lowland and hill forest.

Because it uses habitat that is also prime for oil palm and pulpwood conversion, most of its range has already been lost.

The classic Sumatran story

The dominant threat is habitat loss. Sumatra has lost more than half of its lowland forest since 1985, mostly to oil palm and industrial plantation forestry. Where forest remains, road access and snaring pressure are increasing.

Because the species is likely occurring at very low densities to begin with, even modest additional pressure could tip local populations to functional extinction.

Camera traps as conservation tools

For a species this hard to see, camera-trap arrays run by Fauna & Flora International, WCS Indonesia and university partners have become the primary conservation tool. They provide the only routine population data.

Effective on-the-ground protection depends on the integrity of Kerinci Seblat and other Sumatran protected areas, which face constant pressure from encroachment.

A species we barely know, still worth keeping

The Sumatran Ground Cuckoo is a reminder that the biodiversity crisis is playing out in species we have only just re-met. Protecting it means holding back the same industrial-scale land conversion that already reshaped most of the island.