Cuckoos (Cuculidae)

19 species in Singapore.

Cuckoos (Cuculidae) are a large, mostly Old World family of medium-sized, slender birds found on every continent except Antarctica, most diverse in the tropics. Most species are arboreal, feeding on insects, especially large, hairy caterpillars avoided by other birds. Some are brood parasites, laying their eggs in other birds' nests and leaving them to raise the young.

The family has both resident and migrant members here. The resident species are much more easily recorded during spring and summer, when they are most vocal. Horsfield's Bronze Cuckoo is one of Singapore's few genuine austral migrants, recorded from May–Aug when it wanders northward from its Australian breeding quarters. Identification challenges in this family include the Cacomantis cuckoos, the hawk-cuckoos (especially Malaysian and Hodgson's Hawk-Cuckoo), and Little and Horsfield's Bronze Cuckoo.

This is a diverse family with species that have equally diverse habitat preferences. Chestnut-bellied Malkoha is perhaps the most forest-dependent, as Violet Cuckoo occasionally turns up in more open landscapes when their preferred caterpillar prey are abundant. Most of the remaining species tolerate a wide range of habitats ranging from parkland to forest, and the famous "uwu" bird – Asian Koel – is particularly fond of urban areas, much to the dismay of some. Lesser Coucal is more or less restricted to grassland and open scrub, along with Jacobin Cuckoo, which is a vagrant.

Cuckoos here are mostly solitary. Many can be easily overlooked as they spend much of their time in the canopy, where they glean leaves and branches for caterpillars. Unlike other members of the family, coucals spend most of their time in the undergrowth and on the ground, occasionally sunning themselves on open perches. The resident species are seasonally more vocal and are often heard before seen during their months of peak activity.