It is not often that two species from different families can be confusing. More so when they share the same common name as in the case of the Crow-billed Drongo Dicrurus annectans and the Squared-tailed Drongo Cuckoo Surniculus lugubris. Both are black and have more or less the same structure as each other. But look closer and you will find distinctive features in each species to tell them apart. The Crow-billed Drongo is a winter visitor and passage migrant to Singapore while the ST Drongo Cuckoo is a breeding resident with a few visiting during the winter months. If you see one during the summer months, it will be the Squared-tailed Drongo Cuckoo. They are very vocal all over our forests in May during breeding.
First Winter Crow-billed Drongo Adult Square-tailed Drongo Cuckoo
From the above photos, the differences are quite easy to pick out. First look, the Square-tailed Drongo Cuckoo has a slimmer look giving it a longish appearance. The Crow-billed Drongo looks broader.
The bill of the Cuckoo is thinner and slightly decurved, typical of all cuckoos, while the Drongo has an unmistakable broad bill from whence its name is derived.
Only the underside of the tail of the Cuckoo has scattered white barrings on it like most cuckoo species while the tail of the Drongo is unmarked.
The last feature is the shape of the tail. The Cuckoo has more or less a square tail sharing the characteristics of all cuckoos while the Drongo has a forked tail flaring outwards quite a bit.
A first winter Crow-billed Drongo on passage was photographed at Bidadari on the 19th of September by Lim Ser Chai. This is the first arrival for this season but stayed for less than 2 days.