Phaëthon aethereus mesonauta Peters
Red-billed Tropic-bird
Phaëthon aethereus mesonauta Peters, Occ. Papers Boston Soc. Nat. Hist., 5, 1930, p. 261. (Type locality, Swan Key, Almirante Bay, Panama.)
Phaeton aethereus Finsch, Ibis, 1880, pp. 329, 333, (Ratak Chain, Marshalls); idem, Journ. f. Ornith., 1880, p. 310 (Kuschai); idem, Ibis, 1881, p. 109 (Kuschai); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 73 (Kushai, Marshalls); Ogilvie-Grant, Cat. Birds British Mus. 26, 1898, p. 457 (Kushai, Marshalls); Schnee, Zool. Jahrbücher, 20, 1904, p. 390 (Marschall Inseln); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 34 (Kusaie, Marshall Islands).
Phaethon aethereus [?mesonauta] Hand-list Japanese Birds, rev., 1932, p. 187 (Kusaie, Marshalls); Hand-list Japanese Birds, 3d ed., 1942, p. 208 (Kusaie, Marshall Islands).
Geographic range.—Tropical parts of Atlantic and eastern Pacific from Cape Verde Islands west to Panama and Galapagos Islands. In Micronesia: Caroline Islands—Kusaie; Marshall Islands—Ratak Chain.
Characters.—Adult: A large, white sea bird with a long white tail; dorsal surface marked with blackish, transverse vermiculations; bill red; tarsus and foot flesh-colored with a yellowish hue, with plantar surface grayish. Immature: Resembles adults but dark transverse bars are broader; crown blacker; bill yellow.
Remarks.—No specimens have been examined. The Red-billed Tropic-bird is placed in the list of birds known from Micronesia on the basis of two observations by the German ornithologist, Otto Finsch. It has not been reported since his time, and may be considered as an unusual record for the area. I am following the Hand-list of Japanese Birds (Hachisuka et al., 1942:208) in assigning the bird to the subspecies, P. a. mesonauta.