The three species of tropic birds known from Micronesia overlap very little in their ranges in this area. The White-tailed Tropic Bird has become firmly established in the western part of Micronesia, but there are only a few records from the extreme eastern part. The Red-tailed Tropic Bird appears to be resident only in the northern Marianas although it has been recorded in the Carolines and Marshalls. Interspecific competition may prevent considerable intermingling of breeding populations in Micronesia, or it may be that each species requires different ecologic conditions. =Sula dactylatra personata= Gould Masked Booby _Sula personata_ Gould, Proc. Zool. Soc. London, 1846, p. 21. (Type locality, North and northeast coasts of Australia = Raine Island.) _Sula cyanops_ Finsch, Ibis, 1880, p. 219 (Taluit); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 72 (Marshalls); Ogilvie-Grant, Cat. Birds British Mus., 26, 1898, p. 430 (Marshalls). _Parasula dactylatra personata_ Kuroda, in Momiyana, Birds Micronesia, 1922, p. 35 (Marshall Islands); Mathews, Syst. Avium Australasianarum, 1, 1927, p. 232 (Marshall Islands). _Sula dactylatra personata_ Yamashina, Tori, 7, 1932, p. 407 (Medinilla); Hand-list Japanese Birds, rev., 1932, p. 187 (Medinilla, Marshall Islands); Hand-list Japanese Birds, 3d ed., 1942, p. 208 (Medinilla, Marshall Islands). _Geographic range._--Central and western Pacific from the Hawaiian Islands south to Australia, probably also in the Indian Ocean. In Micronesia: Mariana Islands--Medinilla; Marshall Islands--Jaluit? _Characters._--Adult: A large, white sea bird, with brown wings and tail; face dark blue; bill horn-colored with base orange-yellow in males and pink or light red in females; feet olive in males and lead gray in females. Immature: Resembles adult, but head, wings, tail, chin and throat dark brown; some white mottling may be present on back and rump; bill dark; feet lead colored. _Nesting._--Yamashina (1932a:407) reports the taking of 12 eggs on February 19, 1931, at Medinilla Island in the Marianas. _Remarks._--No specimen has been examined by me from the area reported upon. Little is known regarding the distribution of the Masked Booby in Micronesia. It is found on the island groups which surround Micronesia and future field observations probably will add to our knowledge of its occurrence in this area. It is known to be resident only in the northern Marianas. =Sula sula rubripes= Gould Red-footed Booby _Sula rubripes_ Gould, Syn. Birds Australia, pt. 4, 1838, app., p. 7. (Type locality, New South Wales = Raine Island.) _Pelecanus piscator_ Kittlitz, Obser. Zool., in Lutké, Voy. "Le Séniavine," 3, 1836, pp. 296, 299 (Lougounor = Lukunor); _idem_, Denkw. Reise russ. Amer. Micron. und Kamchat., 1, 1858, p. 351 (Lugunor).