Colluricincla tenebrosa (Hartlaub and Finsch)
Palau Morning Bird
Rectes tenebrosus Hartlaub and Finsch, Proc. Zool. Soc. London, 1868, p. 6. (Type locality, Pelew Islands.)
Rectes tenebrosus Hartlaub and Finsch, Proc. Zool. Soc. London, 1868, p. 118 (Pelew Islands); idem, Proc. Zool. Soc. London, 1872, pp. 89, 99 (Pelew); Finsch, Journ. Mus. Godeffroy, 8, 1875, pp. 4, 18, pl. 3, fig. 1 (Palau); Schmeltz and Krause, Ethnogr. Abth. Mus. Godeffroy, 1881, p. 407 (Palau); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 27 (Pelew).
Colluricincla tenebrosa Gray, Hand-list Birds, 1, 1869, p. 386 (Pelew); Dubois, Syn. Avium, 1, 1902, p. 496 (Pelew); Mayr, Amer. Mus. Novit., no. 1269, 1944, p. 5 (Palau); idem, Birds Southwest Pacific, 1945, p. 297 (Palau); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 69 (Peleliu, Ngabad, Garakayo).
Pinarolestes tenebrosus Sharpe, Cat. Birds British Mus., 3, 1877, p. 298 (Pelew); Matschie, Journ. f. Ornith., 1901, p. 112 (Palau); Reichenow, Die Vögel, 2, 1914, p. 296 (Palau); Takasukasa and Kuroda, Tori, 1, 1915, p. 54 (Pelew); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 69 (Pelew); Hand-list Japanese Birds, rev., 1932, p. 174 (Palau).
Myiolestes tenebrosus Tristram, Cat. Birds, 1899, p. 188 (Pelew).
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).
Molt.—The molting process in this species seemingly takes place from August until December. Most of the birds taken by the NAMRU2 party in August and September were in molt. Molting specimens were obtained by Coultas in October, November and December.
Food habits.—The Palau Morning Bird feeds on plant and animal materials. Stomachs obtained by the NAMRU2 party contained green plant material, seeds, insect parts, and grit. The bird feeds principally on the ground or in low bushes.
Remarks.—The Palau Morning Bird is a thrushlike bird which spends its time on or near the ground in areas where ground cover is thick. In 1945, the NAMRU2 party found the bird in the thick matting of vines which had covered over the battle-cleared areas. I did not find the bird at elevations of more than three to four feet above the ground. When flushed, it would flutter a short distance and disappear into the brush. It has a sweet song and may be considered as one of the finest singers in Micronesia. It heralds the break of day with its melodious carol, and its name is derived from its calling early in the morning. I heard the bird only infrequently in the hot part of the day, although it would sing when the skies were overcast. Its song could be heard also as evening approached. The bird is moderately common, and evidently is more abundant on the smaller islands than on Peleliu. Its occurrence on the smaller islands was noted also by Coultas.
The taxonomic status of the Palau Morning Bird has been one of uncertainty as shown by the fact that the bird has been treated under six generic names since its discovery by Captain Tetens. Mayr (1933a:5) erected a new genus, Malacolestes, for the morning bird pointing to its differences from "Rhectes (= Pitohui) and Pinarolestes (= Myiolestes)." Later, he (1944b:5) disregards this name and places the bird in the genus Colluricincla stating that its special characters "are due to isolation." This treatment is followed here. The Palau Morning Bird is the most northern representative of a group of birds which have their center of dispersal in the New Guinea and Australian area. As Mayr has pointed out, C. tenebrosus appears closest to the C. megarhynchus group of New Guinea. These species have bills of similar shape, coloration which is darker above and lighter below, soft feathers on underparts, and streaked appearance of throat and breast. The resemblances between C. tenebrosus and C. megarhynchus might be such as to indicate that these are merely subspecifically distinct from each other.