Izu Thrush

The Izu thrush, which is observed solitary or in small flocks of two or three birds (3), breeds primarily between March and June, when it lays between two and five eggs (2). The nest, situated on a low branch or occasionally on the ground, is made of grass and leaves, stuck together with mud and covered with moss (2). The Izu thrush forages in the forest canopy, on the ground, in leaf litter, and in more open areas adjacent to woodland. It feeds on fruits, seeds and invertebrates, particularly caterpillars, and brings earthworms, insects and centipedes to the nestlings (2).

The Izu thrush is on the Red List of Japan, which means that its conservation importance is recognised (3). The Izu Islands lie within the Fuji-Hakone-Izu National Park (5), and several places have been designated as “special protected areas”, but there are no park rangers, and the destruction and alteration of habitat continues on many of the islands (4). The maintenance of suitable forest habitat is important for the conservation of the Izu thrush, and thus enforcement of the National Park is essential. This is required in addition to the control of predators, for example, by introducing new controls on the dumping of garbage to reduce the numbers of large-billed crows (3).

The Izu thrush, named after the group of Japanese islands on which it occurs, has richly coloured plumage; brownish-russet on the upperparts and orange-red on the breast and flanks. The wings and tail are blackish, and the centre of the belly is white. A yellowish bill and narrow yellow ring around the eye contrasts with the male's black head and upper breast. The female has a dark brown head and white throat, streaked with black. Juveniles have brown plumage with buff streaking on the upperparts (2).

Occurs in mature, deciduous woodland, preferably with a well-developed canopy and a sparse shrub layer. It can also be found in adjacent open areas such as ploughed farmland, gardens and roadsides, where it feeds (2).

Endemic to Japan, where it occurs on the Izu Islands, and on the northern Nansei Shoto (or Ryukyu) Islands (3).

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1).

The Siberian weasel, Mustela sibirica, which was introduced onto Miyake-jima Island, preys on eggs and chicks in the nest, and appears to have caused a significant decline in the number of Izu thrushes. Nest predation by large-billed crows, Corvus macrorhynchos, has also increased due to raw garbage becoming a more familiar sight in the Izu Islands, and domestic cats also prey on nests and fledglings. The impact of predation has been compounded by the ubiquitous threat of habitat loss. On many of the Izu Islands, natural forest has been destroyed for timber production, road construction and tourism development (3) (4). An additional, natural threat is volcanic eruptions on Miyake-jima. An eruption in 2000 covered the island in a fine layer of ash, killing many forest-dwelling insects. This does not appear to have affected the Izu thrush to the same extent as other birds on the island, but the emission of deadly gases from the volcano crater could still prove to have a damaging effect on Izu thrush populations (3).