Northern Hawk-Cuckoo Hierococcyx hyperythrus Scientific name definitions

28–30 cm; 92·5–147·8 g. A smallish hawk-cuckoo; adult generally slate-grey above , including cheeks and chin, with narrow whitish vertical stripe from base of bill (sometimes extending in front of eyes) to chin, and some have large white patch on nape or hindcollar (retained from subadult plumage?); wings brownish grey, sometimes faintly edged rufous on remiges; tail  grey with 3–4 black bars (and some rufous), the subterminal band fairly broad and the terminal one even wider and tipped rufous and white; most of throat white, lower cheeks and rest of underparts  rusty pink, sometimes with grey bases to feathers affording a slightly scaled effect; undertail-coverts white; iris brown to orange-brown or dirty white, eyering yellow, bill black becoming greenish yellow basally, and legs and feet yellow. Juvenile is dark grey-brown above with buff edgings to the feathers, blackish throat, and rest of underparts white, streaked and spotted blackish from throat to belly; subadult has grey head tippe buff, dark grey-brown upperparts barred rufous, sometimes some white on nape, and underparts white marked with dark brown chevrons, spots or streaks.

NE China, Ussuriland and Sakhalin, and S to Korea, Japan and SE China; winters S to Borneo.

Most vocal during periods of overcast weather, drizzly conditions or at twilight. Far-carrying long call, “weeteetiditdidididittitititititititi” can sound almost painful to the ears, being loud, shrill and becoming steadily higher-pitched, climaxing, and then ending more calmly, or a crescendo with higher, long, screeches and short “pee” notes; also a “ju-ichi, ju-ichi”, or “weeweepeeit”, alternatively “weeweepeeweit”, or a buzzing whistled “wee wee-pit”.

Season is May–Aug in Japan and probably late May–Jul in South Korea. Brood-parasite, known to lay eggs in nests of the following species in Japan: Eurasian Skylark (Alauda arvensis, rarely), Japanese Thrush (Turdus cardis), Brown-headed Thrush (T. chrysolaus), Japanese Robin (Larvivora akahige), Siberian Blue Robin (Larvivora cyane), Orange-flanked Bush-robin (Tarsiger cyanurus), Common Stonechat (Saxicola torquatus), Asian Brown Flycatcher (Muscicapa dauurica), Narcissus Flycatcher (Ficedula narcissina), Blue-and-white Flycatcher (Cyanoptila cyanomelana, thought to be a primary host in South Korea), Olive-backed Pipit (Anthus hodgsoni) and Japanese Paradise-flycatcher (Terpsiphone atrocaudata). Eggs reported to be pale blue, perhaps also greenish light blue (although doubts have been expressed about the latter), size 28 mm × 20 mm; incubation period unknown. Nestling initially has pinkish skin, but soon becomes blackish above and yellow below, with yellow gape and inner mouth pink with dark lines; as plumage develops, acquires gape-coloured patches on wings, thereby simulating gaping display of more than one nestling to acquire additional food; nestling period 19–20 days. No further information.