_Halcyon chloris owstoni_ Takatsukasa and Yamashina, Dobutsu. Zasshi, 43, 1931, p. 484 (Asuncion); Hand-list Japanese Birds, rev., 1932, p. 180 (Asuncion); Hand-list Japanese Birds, 3d ed., 1942, p. 200 (Assongsong, Pagan, Almagan); Mayr, Birds Southwest Pacific, 1945, p. 293 (Almagan, Pagan, Agrigan, Asuncion); Peters, Checklist Birds World, 5, 1945, p. 209 (Asuncion, Pagan, Alamagan); Borror, Auk, 64, 1947, p. 417 (Agrigan). _Geographic range._--Micronesia: Mariana Islands--Asuncion, Agrigan, Pagan, Almagan. _Characters._--Adult: Resembles _H. c. albicilla_, but hind part of crown blue-green and black collar broader. Immature: Resembles adult, but forehead buffy and edges of feathering on anterior crown, upper wing-coverts, and tips of secondaries brownish. _Measurements._--Measurements are listed in table 33. _Specimens examined._--Total number, 4 (2 males, 1 female, 1 unsexed), as follows: Mariana Islands, AMNH--Asuncion, 4 (Jan., July). _Remarks._--Marche obtained specimens of this bird at Pagan in November, 1887, and at Agrigan in December, 1888, and in February, 1889. Owston's Japanese collectors obtained birds at Asuncion in 1904, which were named as new by Rothschild. Apparently he used an immature specimen in preparing the diagnosis of his new subspecies. Borror (1947:417) visited Agrigan in 1945 and obtained specimens of this kingfisher. He reports that the bird is a "common and abundant species and probably nests on the island." _Evolutionary history of Halcyon chloris in Micronesia._--_Halcyon chloris_ is distributed from eastern Africa at the Red Sea eastward through southern Asia to Malaysia, Australia and the Pacific islands. Peters (1945:207-213) recognized 47 subspecies within this species. In its colonization of Micronesia, _H. chloris_ apparently arrived first at the Palaus probably from the Philippines or the Moluccas. Whether _H. cinnamomina_ was established at Palau prior to the arrival of _H. chloris_ is unknown. _H. chloris teraokai_ dominates most of the available habitats at Palau, although it has differentiated but little from subspecies to the west and southwest of Palau. Among named kinds it most closely resembles _H. c. chloris_ (Boddaert) of the Moluccas, Lesser Sundas and adjacent areas in color and structure. The species did not succeed in establishing itself in the Carolines or at Guam, but did so in the Marianas at Rota and northward. In comparison with other subspecies of _H. chloris_ those in the Marianas are characterized by a slight increase in size and a replacement of the bluish-green coloring of the head either partly or wholly by white. It is noteworthy that on the islands of Tinian and Saipan, which occupy a geographically intermediate position in the Mariana chain, the bird has an almost completely white head, whereas the birds on islands to the north and south have only partly white heads.