The problem of plumages and color phases in the Reef Heron has been treated by Mayr and Amadon (1941:4-10). Specimens which they examined from Micronesia were found to be 54 percent gray, 40 percent white, and 6 percent mottled. Of the birds obtained by NAMRU2 field parties, fewer than 40 percent were white. Field counts showed a considerable variation in the ratio of grays to whites: Guam--6 grays to 4 whites; Ulithi--4 grays, 6 whites, 1 mottled; Palau--equal number of grays and whites; Truk--2 whites, 1 gray, 1 mottled. For some unknown reason, the gray birds were more easily approached than the white birds. Gleise and Genelly (1945:221) saw one white Reef Heron at Eniwetok. Wallace (field notes) found white herons more numerous than gray ones at Kwajalein in 1944 and 1945. Borror (1947:417) observed gray birds at Agrigan. Stott (1947:524) saw one blue heron on December 24, at Saipan. The 150 birds seen by him at Lake Susupe in December probably were Plumed Egrets. In discussing the variation in the color phases of the Reef Heron throughout its range, Mayr (1924b:237) suggests that the reduced variability of small populations may not be due to accidental gene loss, but instead to the population having descended from a single pair or from one fertilized female. The descendents would naturally possess only those characters provided for in the genetic make-up of the parents. Reef Herons on New Zealand and in the Marquesas Islands all are gray, while at other island groups different proportions of gray and white individuals occur; such phenomena may result because of the genetic constitution of the "founders." =Nycticorax nycticorax nycticorax= (Linnaeus) Black-crowned Night Heron _Ardes Nycticorax_ Linnaeus, Syst. Nat., ed. 10, 1, 1758, p. 142. (Type locality, Southern Europe.) _Nycticorax griseus_ Hartlaub and Finsch, Proc. Zool. Soc. London, 1872, pp. 89, 105 (Uap); Gräffe, Journ. Mus. Godeffroy, 2, 1873, p. 123 (Yap); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 69 (Uap). _Nycticorax nycticorax_ Sharpe, Cat. Birds British Mus., 26, 1898, p. 146 (Yap). _Nycticorax nycticorax nycticorax_ Kuroda, in Momiyama, Birds Micronesia, 1922, p. 36 (Mackenzie, Yap); Hand-list Japanese Birds, rev., 1932, p. 183 (Yap, Uluthi); Hand-list Japanese Birds, 3d ed., 1942, p. 204 (Yap, Uluthi); Mayr, Birds Southwest Pacific, 1945, p. 302 (Marianas, Yap). _Geographic range._--Europe and Africa east to Japan and Malaysia. In Micronesia: Mariana Islands--Tinian; Palau Islands--Koror; Caroline Islands--Yap, Ulithi, Truk. _Specimens examined._--Total number, 2 immature females, as follows: Palau Islands, USNM--Koror, 1 (Nov. 27); Caroline Islands, AMNH--Truk, 1 (June 18).