Nycticorax caledonicus Hartlaub and Finsch, Proc. Zool. Soc. London, 1868, pp. 117, 118 (Pelew); Sharpe, Cat. Birds British Mus., 26, 1898, p. 158 (Pelew); Hartert, Novit. Zool., 7, 1900, p. 10 (Ruk); Reichenow, Die Vögel, 1, 1913, p. 255 (Palauinseln); Takatsukasa and Kuroda, Tori, 1, 1915, p. 50 (Pelew); Uchida, Annot. Zool. Japon., 9, 1918, p. 486 (Palau); Wetmore, in Towsend and Wetmore, Bull. Mus. Comp. Zoöl., 63, 1919, p. 172 (Uala, Truk Atoll); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 37 (Pelew, Ruk).
Nycticorax manillensis Hartlaub and Finsch, Proc. Zool. Soc. London, 1872, pp. 89, 105 (Pelew); Finsch, Journ. Mus. Godeffroy, 8, 1875, pp. 5, 33 (Palau); idem, Proc. Zool. Soc. London, 1880, p. 577 (Ruk); Schmeltz and Krause, Ethnogr. Abth. Mus. Godeffroy, 1881, p. 353 (Ruk); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 69 (Pelew, Ruk).
Nycticorax caledonicus pelewensis Mathews, Syst. Avium Australasianarum, 1, 1927, p. 200 (Pelew, Carolines); Peters, Proc. Boston Soc. Nat. Hist., 39, 1930, p. 271 (Pelew, Carolines); Peters, Check-list Birds World, 1, 1931, p. 115 (Pelew); Hand-list Japanese Birds, rev., 1932, p. 183 (Palau, Truk); Hand-list Japanese Birds, 3d ed., 1942, p. 204 (Babelthuap, Koror, Coracel, Truk); Amadon, Amer. Mus. Novit., no. 1175, 1942, p. 6 (Palau, Ruk); Mayr, Birds Southwest Pacific, 1945, p. 285 (Palau, Truk); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 43 (Angaur, Peleliu, Garakayo, Truk).
Geographic range.—Micronesia: Palau Islands—Babelthuap, Koror, Coracel, Garakayo, Peleliu, Ngabad, Angaur; Caroline Islands—Truk.
Characters.—Adult: Size medium; head and nape dark slaty-black; occipital plumes white with dark tips and shafts; back dark reddish-brown, lighter on sides of neck, wings, wing coverts, rump, and tail; under parts whitish with light reddish-brown on sides of neck extending to throat and upper breast; tibia with some brownish feathers; underwing pinkish; feet yellowish-brown; bill black.
Immature: Resembles adult, but upper parts mottled black with reddish-brown; underparts with lighter streaks of brown and whitish on breast; feet yellowish; bill black above, yellowish below.
Adult resembles N. c. manillensis Vigors, but is duller above.
Measurements.—Two adult males from Peleliu measure: wing, 293, 299; tail, 105, 107; culmen, 82, 89; tarsus, 79, 81; seven adult females from Peleliu: wing, 269-286 (280); tail, 101-106 (104); culmen, 76-84 (80); tarsus, 78-83 (80); one adult female from Truk: wing, 280; tail, 97; culmen, 83; tarsus, 79.
Specimens examined.—Total number, 27 (5 males, 18 females, 4 unsexed), as follows: Palau Islands, USNM—Peleliu, 9 (Aug. 31, Sept. 1, 5, 6, 8, Dec. 6); AMNH—exact locality not given, 16 (Nov. 7, 8, 13, 23, 25, Dec. 1, undated); Caroline Islands, USNM—Truk, 1 (Feb. 16); AMNH—Truk, 1 (May 25).