Rukia palauensis (Reichenow)
Palau Greater White-eye
Cleptornis palauensis Reichenow, Journ. f. Ornith., 1915, p. 125. (Type locality, Babeldzuap = Babelthuap, Palauinseln.)
Megazosterops palauensis Stresemann, Ornith. Monatsber., 38, 1930, p. 159 (Baobeltaob); Snouckaert, Alauda (2), 3, 1931, p. 26 (Palau); Stresemann, Mitt. Zool. Mus. Berlin, 17, 1931, p. 235 (Baobel Taob = Babelthuap); Mathews, Ibis, 1931, p. 48 (Palau); Hand-list Japanese Birds, rev., 1932, p. 172 (Palau); Yamashina, Tori, 10, 1940, p. 674 (Palau); Hand-list Japanese Birds, 3d ed., 1942, p. 191 (Babelthuap, Peleliu).
Rukia palauensis Mayr, Amer. Novit., no. 1269, 1944, p. 7 (Palau); idem, Birds Southwest Pacific, 1945, pp. 294, 300 (Peliliu); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, pp. 67, 74 (Peleliu).
Geographic range.—Micronesia: Palau Islands-Babelthuap, Peleliu.
Characters.—Adult: A large white-eye with upper parts near "Saccardo's olive" (some individuals darker brown), head and neck more olivacious, rump browner; auriculars blackish with pale yellow streaks; narrow supra-orbital stripe pale olive; orbital ring indistinct; underparts near "olive lake," chin lighter, under tail-coverts light yellowish-brown; wing and tail feathers dark brown, except for tawny outer edges and whitish inner edges; maxilla horn-color; mandible yellowish to tawny; feet tawny; iris grayish-brown.
Measurements.—Measurements of Rukia are listed in [table 52]. Measurements of males and females are comparable within the same species.
Table 52. Measurements of Rukia
Table 52. Measurements of Rukia
| Species | No. | Wing | Tail | Culmen | Tarsus |
| R. palauensis | 19 | 80 | 54 | 21.5 | 25 |
| (76-84) | (51-57) | (20.0-22.5) | (24-26) | ||
| R. ruki | 8 | 81 | 52 | 21.5 | 23 |
| (76-85) | (51-52) | (20.0-23.0) | (22-24) | ||
| R. sanfordi | 18 | 70 | 44 | 23.0 | 21 |
| (67-71) | (41-47) | (22.0-24.0) | (20-22) |
Specimens examined.—Total number, 21 (12 males, 9 females), as follows: Palau Islands, USNM—Peleliu, 11 (Aug. 27, 29, 30, Sept. 4, 5, 6, 7, Dec. 4, 5); AMNH—Peleliu?, 10 (Dec.).
Molt.—Specimens taken in August and September are in worn plumage, a few individuals show evidence of molt. Specimens taken in December are in fresh plumage, although two or three individuals are in the final stages of molt. This places the period of molt as September, October, and November. Nesting evidently occurs in the summer; one male taken on August 27, 1945, had enlarged gonads.
Remarks.—The Palau Greater White-eye was described under the generic name Cleptornis by Reichenow. This generic allocation was not followed by subsequent authors; Stresemann proposed the generic name Megazosterops in 1930, and Mayr (1944b:7) placed this white-eye in the genus Rukia along with other large white-eyes from Micronesia. In employing this name, Mayr writes, "The generic names Rukia (for ruki) and Kubaryum (for oleaginea) were published simultaneously in the same publication. As first reviser I select the name Rukia, which not only is shorter but is also based on a species which I have been able to examine."
R. palauensis is recorded from Babelthuap and Peleliu of the Palau Islands. In 1931, Coultas found the birds only at the island of Peleliu, where he obtained nine specimens from a flock. In 1940, Yamashina (1940:674) writes that it is a very rare species at Palau. Marshall (1949:219) found the bird at Peleliu but at no other islands visited. In 1945, the NAMRU2 party obtained eight specimens at Peleliu from two localities on the eastern side of the island in jungle areas relatively undisturbed by war activities. The birds were fairly common in the brush and vines of the jungle undergrowth at these two areas. There were no flocks seen; usually singles or pairs were noted. The bird bears a striking resemblance to Psamathia annae, which lives in the same environment and has a somewhat similar coloration, shape and posture. These two birds probably have undergone a parallel development. Competition between the two was not noted. Psamathia is evidently less restricted in its distribution.
R. palauensis has a restricted distribution in the Palau Islands, as indicated by the observations of Coultas, the Japanese and the NAMRU2 party. The disturbance resulting from the war activities has undoubtedly influenced the population and restricted further the preferred habitat of this white-eye, especially at Peleliu.