Izu Thrush Turdus celaenops Scientific name definitions

23 cm. Male  has black hood to lower breast, rich brownish-russet upper­parts , blackish wings and tail; chestnut-orange upper belly  and flanks, white mid-belly to dark-streaked vent; yellowish bill  , narrow yellow eyering; brownish legs. Female  is like male, but head dark brown, whitish throat, dark brown malar and throat streaks. Juvenile is brown with buff streaking above, diffuse buff submoustachial and throat, dark brown malar, buffish with spotting below.

N Ryukyu Is (Yakushima, Tokara Is) and Izu Is (from Toshima to Aogashima); some move to islands S of Kyushu, Oshima and adjacent S Honshu in winter.

Fruit, seeds and, in summer, mainly invertebrates ; focuses on caterpillars in canopy during Apr–Jun. Main food brought to nestlings was earthworms (64%), insects (14%) and centipedes (10%). Forages mainly in canopy and on ground amid leaf litter, also in more open areas adjacent to forest cover.

Song  , from low perch, mid-Mar to early Jul, a series of 3–5 buzzing trills, “tsurrrrrr… turrrrrr… tzurr­rrrrr… tsizi”, deeper than those of Larvivora akahige, each trill changing pitch and with middle part sharper, as if inhaling, sometimes without brief concluding “tsizi”, sometimes interspersed with abrupt “chik!” notes. Alarm a bubbling call, deeper and more guttural than that of T. pallidus and T. chrysolaus.

Mar–Jun on Miyake-jima, rarely into Aug, peak in May; similar period on other islands inferred from various records of nests and nestlings; most pairs single-brooded. Nest made of grasses and leaves, plastered with mud, covered in moss, placed 1·5–6 m up on low branch, sometimes on ground. Eggs 2–5, usually 3–4, clutch size apparently related to mean temperature in Apr (on average, larger clutches in warmer years), eggs white, pale brown or pale green with red-brown to purple markings; no information on incubation and fledging  periods. Breeding success on Miyake-jima 85% in 1985 study and 71–78% in 1978–1980, but only 7·3% in 1991.

VULNERABLE. Restricted-range species: present in Izu Islands EBA. Population placed in range 2500–10,000 (probably never greater than this owing to tiny range), and considered declining because of impacts of introduced species. Densities variable: in 1973, roadside transects in several of the Izu islands yielded (per km) 5·7 and 3·8 birds on To-shima, 0·7 on Nii-jima, 7·3 on Mikura-jima, 2·5 and 1·7 on Hachijo-jima, and 12·5 and 13·8 on Aoga-shima. In recent review, 34 localities mapped of which only twelve known to involve post-1980 records. Nest and fledgling predation by Siberian weasel (Mustela sibirica), introduced on Miyake-jima in 1970s to control rabbits, and by Large-billed Crows (Corvus macrorhynchos) and domestic cats is the main threat. Crow populations on Miyake-jima and certain other islands have risen dramatically in response to increased refuse-dumping, an issue that needs to be addressed. Of 22 nests with eggs found in 1992 on Miyake-jima, all were preyed on at nestling stage. Extent of changes in thrush populations unclear, as threats not present on all islands. Important population on Miyake-jima most obviously affected: roadside transects in 1978–1980 found 24·4, 33·4 and 28·8 birds/km, this falling to 6·7 and 11·1 birds/km in 1991; population may also have been affected by major volcanic eruption in Aug 2000. Entire Izu Archipelago designated a national park, several important sites are special protection areas, and a small sanctuary (nature centre) exists on Miyake-jima. Detailed ecological studies, stronger park management and intensive control of nest predators now needed. Protected by Japanese law.