Specimens examined.—Total number, 37 (15 males, 19 females, 3 unsexed), as follows: Palau Islands, USNM—Babelthuap, 1 (Nov. 27)—Koror, 3 (Nov. 4, 5)—Garakayo, 6 (Sept. 18)—Peleliu, 5 (Aug. 27, Sept. 10); AMNH—exact locality not given, 22 (Oct., Nov., Dec.).
Molt.—Many of the specimens of Z. c. finschii taken in the period from August to December show evidences of molt. Some of the birds taken in November and in December appear to be in fresh plumage. All three subspecies of Z. cinerea evidently undergo a period of molt in the late summer and fall.
Remarks.—The Micronesian Dusky White-eye of Palau was found on several of the islands of the southern Palaus by the NAMRU2 party in 1945. The bird was observed in flocks of five or more individuals moving rapidly through the foliage of trees and shrubs. It was not found in the dense, undisturbed jungle areas, but rather in second growth vegetation and along the margins of woodlands. At Peleliu, birds were noted in trees and shrubs along the roadways; at Garakayo, birds were seen in low trees near the summits of hills. At Garakayo, Z. cinerea and Z. conspicillata were found in the same areas near the tops of the hills. Both species appeared to be feeding on seeds of the same trees (unidentified but resembling the hibiscus). Z. cinerea was more numerous than Z. conspicillata and appeared (from observations made on September 18, 1945) to be the dominant species and was seen to chase the smaller Z. conspicillata away. Coultas (field notes) found Z. cinerea "fairly common" in 1931 at Palau.
Evolutionary history of Zosterops cinerea.—The dusky white-eyes of Micronesia were considered as separate species until 1944, when Mayr (1944b:7) treated them as conspecific, stating that the bird at Ponapé has characters intermediate between those at Kusaie and Palau. Earlier, Hartert (1900:3) suggested a close association between Z. cinerea and the species at Truk (now Rukia ruki). Mayr concludes that Z. cinerea and R. ruki are not closely related, and points out that the absence of a white orbital ring in Z. cinerea does not necessarily mean that the bird should be considered as belonging to a genus other than Zosterops.
The pathway of colonization and the ancestral stock of Z. cinerea are not certainly known. Among the white-eyes of the Polynesian, Melanesian and Malayan areas, there are few kinds which Z. cinerea resembles closely. Mayr (1941b:204) writes that the Z. cinerea at Ponapé was derived from either Polynesia or Papua. I find little in common between Z. cinerea and the species in these areas, and in my opinion Z. cinerea is closest to Z. atriceps of the Moluccas. Z. atriceps has plumage which is part grayish and part brownish. Its underparts resemble those of Z. c. cinerea but are paler gray; crown, neck, and shoulder much like that of Z. c. ponapensis and Z. c. finschii; and bill resembling that of Z. c. cinerea. Z. atriceps differs by having olive-green coloring on back and wings and yellowish coloring on under side of tail. Thus, it is possible that Z. cinerea invaded Micronesia from the Moluccan region, reaching either Palau or Ponapé initially.
Rukia palauensis (Reichenow)
Palau Greater White-eye
Cleptornis palauensis Reichenow, Journ. f. Ornith., 1915, p. 125. (Type locality, Babeldzuap = Babelthuap, Palauinseln.)