Melanesian Component
The Papuan or Melanesian Region (New Guinea, Bismarck Archipelago, Solomon Islands) has supplied to Micronesia its greatest number of endemic land and fresh-water residents. Fifty kinds of birds belonging to the following species reached Micronesia from Melanesia: Nycticorax caledonicus, Megapodius lapérouse, Ptilinopus roseicapillus, Gallicolumba xanthonura, G. canifrons, Caloenas nicobarica, Halcyon cinnamomina, Trichoglossus rubiginosus, Collocalia inquieta, Edolisoma tenuirostre, Rhipidura rufifrons, Metabolus regensis, Monarcha godeffroyi, M. takatsukasae, Colluricincla tenebrosa, Aplonis opacus, A. pelzelni, A. corvinus (extinct?), Cleptornis marchei, Myzomela cardinalis (probably by way of Southern Melanesia), Rukia palauensis, R. oleaginea, R. ruki, R. sanfordi, Erythrura trichroa. The colonization of Micronesia by these species has probably extended over a considerable period of time. Megapodius, Trichoglossus, and Aplonis corvinus may represent older colonizations which have become well differentiated from the ancestral forms; Nycticorax, Myzomela, and Erythrura may have become established later and have had "less time" to become modified from the ancestral forms. Birds from Melanesia have reached Micronesia probably by direct flight to the Caroline Islands. Aided by favorable winds which blow from the southwest, south and southeast during the period from May to November, birds, particularly the young of the year, might conceivably be blown in the direction of the Carolines, where 57 percent of the birds derived from Melanesia reside. The Palaus are populated with 15 percent, the Marianas with 28 percent, and the Marshalls (lacking "high" islands) with none; these may be secondary colonizations from the Carolinas excepting Ptilinopus, Megapodius, Gallicolumba canifrons, Cleptornis, and Colluricincla. The Marshall Islands have received no avian components from Melanesia. The absence of "high" islands in the Marshalls and the possible inability of birds accustomed to life on the luxuriant islands of Melanesia to become established on relatively barren atolls are logical reasons for this. Instead of New Guinea itself, the outlying islands of Melanesia (Bismarck Archipelago, Solomons, Southern Melanesia) probably have been the principal "taking-off" places for birds invading Micronesia.
Moluccan and Celebesian Components
Birds which reached Micronesia by way of the islands of Celebes and the Moluccas may have been derived originally from Melanesia. The following birds appear to have used this route: Porphyrio porphyrio, probably Halcyon chloris, Rhipidura lepida, Myiagra oceanica, Zosterops conspicillata, and Z. cinerea. These birds apparently became established initially in the Palaus; Porphyrio and Rhipidura lepida have not been recorded elsewhere in Micronesia, but Myiagra and the two species of Zosterops have spread to the Carolines and Marianas, although not into the Marshall Islands. Wind from the southeast in summer and fall has probably been a factor aiding these colonizations. The population of Gallinula chloropus resident at Palau may also have arrived by this route.
Philippine Component
Ten of the kinds of birds of Micronesia have come from or by way of the Philippine area. These are known principally from the Palaus and the Marianas and include: Rallus philippinus, R. owstoni, Poliolimnas cinereus, Caprimulgus indicus, Corvus kubaryi, Psamathia annae, Artamus leucorhynchus, possibly Lonchura nigerrima, and Collocalia inexpectata. The Philippines may have been the actual point of dispersal of the birds (example, Psamathia), or may have been used as a stepping stone to Micronesia by birds coming from Melanesia (examples, Rallus and Artamus), by birds from Malaysia (example, Collocalia), and by birds from Asia (example, Caprimulgus). Two birds of this component have reached the islands of eastern Micronesia. A subspecies of Lonchura nigerrima is endemic at Ponapé, and a subspecies of Poliolimnas cinereus occurs on several islands in the Carolines and has even been recorded at Bikini in the Marshall Islands. Three species are known only from the Palaus; two are known only from the Marianas.
Palearctic Component
Fig. 8. Faunal areas from which the resident land birds and fresh-water birds of Micronesia have been derived. (1) Palearctica; (2) Philippines; (3) Moluccas and Celebes (Malaysia); (4) Melanesia (New Guinea and northern Melanesia); (5) Polynesia.