Caleya tenebrosus Mathews, Syst. Avium Australasianarum, 2, 1930, p. 649 (Pelew).
Malacolestes tenebrosus Mayr, Amer. Mus. Novit., no. 590, 1933, p. 5 (Palau); Hand-list Japanese Birds, 3d ed., 1942, p. 193 (Babelthuap, Koror, Peliliu).
Geographic range.—Micronesia: Palau Islands—Babelthuap, Koror, Garakayo, Peleliu, Ngabad.
Characters.—Adult: Upper parts between "snuff brown" and "bister," head blacker; chin, throat, and upper breast like upper parts but darker; lower breast and abdomen lighter and more buffy, sides darker; feathers of underparts with darker shafts producing a streaked appearance; underside of wing and under tail-coverts light-colored; bill dark brown; feet lighter brown; iris yellowish. Female smaller.
Immature: Resembles adult, but head and neck lighter; ear-coverts, sides of neck, throat, upper breast darker; lower breast and abdomen paler.
Measurements.—Measurements are listed in [table 43].
Table 43. Measurements of Colluricincla tenebrosus
Table 43. Measurements of Colluricincla tenebrosus
| Number and Sex | Wing | Tail | Full Culmen | Tarsus |
| 20 males | 104 | 76 | 23.5 | 31 |
| (100-107) | (73-79) | (22.5-24.5) | (29-31) | |
| 9 females | 97 | 73 | 23.0 | 30 |
| (94-101) | (71-76) | (22.0-24.0) | (30-31) |
Specimens examined.—Total number, 32 (21 males, 11 females), as follows: Palau Islands, USNM—Koror, 6 (Nov. 5, 18)—Garakayo, 3 (Sept. 18)—Peleliu, 5 (Aug. 29, 30, Sept. 1, 6)—Ngabad, 2 (Sept. 11); AMNH—exact locality not given, 16 (Oct. 8, 13, 26, Nov. 11, 13, 17, 19, 21, 23, Dec. 9).