Comparison of Indian CuckooCuculus micropterus and Common CuckooC. canorus. Common is bottom left—note yellow iris and compare to dark iris of Indian bottom right. Top panels also Indian. Note thick barring on underparts. Cape Nanhui, Shanghai, May. (Craig Brelsford)
Indian CuckooCuculus micropterus micropterus has summer range in China that falls mainly on eastern side of diagonal line running from northeast to southwest China. Resident Hainan. Smaller than Common Cuckoo, but size alone rarely enough for positive identification. Best differentiator is voice, and Indian Cuckoo is instantly recognizable, the loud, four-syllable whistle being commonly heard in wooded areas throughout its range. Song heard mainly in breeding areas, making ID of migrating and wintering birds difficult. All five Cuculus cuckoos in China (Indian Cuckoo, Common Cuckoo, Himalayan Cuckoo, Lesser Cuckoo, and Oriental Cuckoo) are long-tailed and slender, with adults having grey hood and similarly colored grey upperparts. Tail darker than upperparts, approaching black, with some white spotting. Underparts whitish, with black bars (fainter on lower belly and vent). Legs short, yellow; wings long, pointed. All arboreal and insectivorous, with caterpillars in particular being taken, and in their rapid flight can be mistaken for falcons or hawks. All are brood parasites. Indian Cuckoo has a black subterminal band on its tail, which the other similar cuckoos lack. Bill yellow at base, with black tip; eye-ring yellow. Eye of Indian Cuckoo is darker than Common, and rump of Indian contrasts less with its body. Female tends more toward brown in upperparts and has rufous wash across top of breast, sometimes extending to sides of neck. Juvenile blackish grey-brown with prominent white tips to feathers; the most distinctive of the similar Cuculus species. Indian Cuckoo mainly parasitizes the nests of crows and drongos, notably Ashy Drongo. — Craig Brelsford
One of the many reasons I love spring is that during this time cuckoos call and are easier to identify. On Tues. 17 May at Cape Nanhui, the birding hotspot in Pudong, Kai Pflug and I had two calling cuckoos: Indian CuckooCuculus micropterus and Common CuckooC. canorus. I got photos of both. Can you see differences in the appearance of Common and Indian? One is eye color. The other is the thickness of the barring on the underparts. Indian also is smaller than Common, but the size difference is harder to see.
Here is one of the best-known bird calls in the world, that of Common Cuckoo, recorded by me at Cape Nanhui on 17 May (00:31; 2 MB):