Rollin H. Baker

“ The cicada birds probably invaded Micronesia along two independent routes from a dispersal center in the Papuan area. The form at Palau, E. t. monachum, resembles closely several of the subspecies to the south and southwest, particularly those in the New Guinea area. Aside from the smaller size of the Palau form there are differences in coloration between this bird and those of Melanesia. In the adult female and the juvenile there are differences in the amount of barring on the underparts and in the shade of color on the upper parts. ”

“ The distribution of several species has not been completely investigated, especially those land birds (Ducula, Ptilinopus, and Aplonis) which inhabit coral atolls in the Carolines and Marshalls. The bird life of the northern Marianas is also incompletely known. Continued observations in the Micronesian islands will increase our knowledge of the kinds of migratory shore birds and migratory land birds which reach the island as winter visitors. Further information is needed concerning the breeding activities of sea birds in Micronesia, especially in the Marshalls and Carolines. ”

“ It is my opinion that Rukia is a valid genus and is as much different from the genus Zosterops (or more so) than other recognized genera of large white-eyes (Woodfordia and Apoia) . There is also the strong possibility that the large white-eyes of Micronesia have been derived from more than one source (and are falsely united in one genus) ; however, it is my feeling that they represent a single colonization, which successfully established itself at four islands and evolved into four divergent species. Possibly R. oleaginea is the least specialized and is closest to the ancestral stock ”

“ In Micronesia the Common Noddy Tern is not a conspicuous bird except during its breeding period. Probably it spends most of its life at sea, being unlike Gygis alba in this respect. Large flocks seem less wary of man than are small groups and singles, which are often easily disturbed. Birds of this species appear to prefer the low atolls and offshore islets where both tall vegetation and bare ground are utilized for nesting or roosting. ”

“ The male was much more in evidence than the female and was frequently seen flying high over the roadways and jungle areas; eighty percent of the ground doves seen while road-counts were being made were males. The female was found less frequently; it was a less conspicuous bird and was seen only occasionally in flight. Neither sex appeared to have the secretive, terrestrial habits of G. canifrons of the Palau Islands. On the basis of our observations at Guam, I would say that the name "ground dove" for the bird at Guam is not descriptive. ”

“ For shore birds, there appears to be a migration route extending almost due south from the Riu Kiu and the Japanese islands to the Palau Islands. Some birds may migrate via the Philippines and others may pass to the east of the Philippines. This route is considered to be distinct from that used by birds which follow the Asiatic Coast and coastal islands, because the Palau Islands are situated approximately 600 miles east of the Philippines. Moreover, there are fewer species—only 20 recorded from the Palaus as compared with the number recorded from islands closer to the mainland of Asia. ”

“ Once a population has become established and "adjusted" to a given environment on a small island, intraspecific competition might bring about adaptative selection. Subsequent colonists might be eliminated by the competition brought about by these previously adapted organisms, especially if both organisms were adapted for life in the same ecologic niche. Space restriction may be important in such Micronesian birds as Rhipidura and Myiagra, which appear to possess recognizable territories. A new colonist entering the territory of one of these birds might be forced out. ”

“ The committee that prepared the Hand-list of Japanese Birds (Hachisuka et al., 1942:222) points out that although many ornithologists believe the Red Jungle Fowl to be introduced in Micronesia and other parts of Oceania, it is their opinion (based on a series of more than 100 skins before them) that the population in Micronesia is racially distinct. They further comment, as did Hachisuka (1939b:600) , that one may find hybrids between these birds and the domestic fowl belonging to the native peoples; this is commonly seen on the more populated islands such as Koror and Saipan. ”

“ The Micronesian islands were first explored and colonized by a a people who came from Malaysia. It is thought that these people spread into the Palau, Caroline, Mariana, Marshall, and Gilbert islands as a single wave of migration. Following this occupation, the people apparently underwent a normal process of cultural evolution [Pg 17] and differentiation. Remains of stone walls, dikes, fences, pillars, graves, and other structures which may be found today at various islands in Micronesia were constructed by the ancestors of the islanders of the present day. ”

“ Adult male in nuptial plumage of A. poecilorhyncha type: "Resembles Anas poecilorhyncha pelewensis from the Palau Islands and Truk Island, but sides of head are browner, superciliary stripes and ground color of cheeks are more buffy. Feathers on upper breast and sides of body are more broadly edged with brown. Speculum is usually violet-purple as in the platyrhynchos type, but in two specimens from Saipan and Tinian, respectively, it is dark green as in Anas poecilorhyncha pelewensis. ”

“ From a flock embarking seaward in "search" of more food, a part or even all of the birds might survive in a chance flight to an isolated island in Micronesia. If a flock containing both males and females reaches an island, the species has a good chance of becoming established. Evidence that such a rapid colonization by flocks of birds can take place is found in the remarkable colonization of New Zealand by Zosterops lateralis from the Australian area. ”

“ In the past, expeditions have visited Micronesia with the aim of obtaining within a short time collections of the animal life as large and as representative as possible. Many of the collectors made few or no field notes on the bird life; some, like Finsch, Kubary, Marche, and Coultas, made valuable observations on the habits of the birds. Intensive ecological researches may be accomplished more thoroughly by resident investigators, who can devote full time to such pursuits. ”

“ Available data indicate that the life spans of individual birds in Micronesia may be short. For example, it was obvious on many of the islands visited by the NAMRU2 party that starlings (Aplonis opacus) in immature plumage outnumbered starlings in adult plumage, although it is possible that immature plumages are retained longer in these island birds than in others. Similar observations were made by Coultas, who noted the ratio of birds in immature plumage to birds in adult plumage at Kusaie to be 5 to 1. ”

“ The fantail is one of the most attractive birds found in the jungles of the Palau Islands. Its bright rufous coloring is conspicuously displayed by the rapid movements of the wings and tail as the bird moves and feeds in the undergrowth. The population is apparently not large, and the individual or pair of birds probably ranges in a relatively large home territory.
Evolutionary History of Rhipidura in Micronesia.—The evolutionary history of Rhipidura in Micronesia has been studied considerably more than that of some of the other genera in the area. ”

“ The starling is primarily a vegetarian; I found no animal matter in stomachs examined at Palau or at Ulithi or Guam. At Palau, as at other islands, more of the starlings seen were in immature plumage than in adult plumage. Coultas (field notes) found the birds to be abundant at Koror and highly prized as food by the natives and Japanese. He writes, "It is surprising what a fine wholesome meal certain people can get out of handful of rice and a starling's breast."
Aplonis opacus guami Momiyama Micronesia Starling
Aplonis opaca guami Momiyama, Birds Micronesia, 1922, p. 9. ”

“ Study of these forms indicates that the Gallinule has colonized the Marianas from Asia probably by way of Japan and the Bonin and Volcano islands. The Hawaiian subspecies is probably of American origin, as pointed out by Mayr (1943:46) , and is not a close relative of the Mariana subspecies. The fact that these insular subspecies have not undergone much differentiation does not necessarily mean that they are recent arrivals, but probably is a reflection of the lack of plasticity of the species; as a whole the species does not exhibit anywhere a great amount of geographic variation. ”

“ Possibly some species of plant-eating birds have reached Micronesia but have failed to establish themselves because of some dietary deficiency caused by poverty of the soils on which the plants grow. If a comparison were made of soils and of the food values of fruits of plants in both the islands of Micronesia and similarly sized islands in the Malay region, a difference might be revealed which would partly explain why some plant-eating birds have not become established in Micronesia. ”

“ The range of the genus Myiagra extends from Australia and Tasmania westward to Timor, northward to the Moluccas, and Micronesia, and eastward to Polynesia. Myiagra oceanica is restricted to Micronesia and consists of four subspecies, which until recently have been considered as four separate species. Unlike many of the species of this genus, M. oceanica shows comparatively little sexual dimorphism. The male of M. oceanica has metallic coloring on the head and the upper back and often has rich, rufous coloring on the breast. The female is less brilliant in coloring, lacking the sheen. ”

“ Perhaps this cuckoo in developing its ability to fly long distances over water on migration has expanded the breadth of its range eastward into the oceanic islands, rather than westward through Malaysia and Melanesia, because it has found less competition from resident birds and from other migrants for feed and habitat. On many of the islands and atolls of the Pacific Basin, this species is the only land bird known. ”

“ The areas of the Moluccas and of Celebes (Malaysia) supplied 21 percent of the birds; the Philippines, 10 percent; Polynesia, 9 percent; and Palearctica, 8 percent. Results of this study show that there may have been only 46 actual colonizations of Micronesia by birds from other areas, and that many of the large number of endemics present have been the result of secondary colonizations within the islands of Micronesia. It is concluded that Micronesia, except for the Marshall Islands, has a much closer affinity to Melanesia than to any other area as regards avifauna. ”

“ Acrocephalus is a friendly bird who does not become frightened easily. He responds to man-made calls."
The Nightingale Reed-warbler is found on many of the islands in the Caroline Chain, including both the "high" volcanic islands (Ponapé and Truk) and the "low" coral islands (Lukunor and Nukunor) . Although the bird has been recorded at Kusaie by Kittlitz and Finsch, it was not taken there by Coultas in 1931. Reed-warblers are unknown at Yap, Ulithi, Fais or at other islands of the extreme western Carolines, or in the Palau Archipelago. ”

“ The bird at Saipan has a longer wing and a deeper bill than the bird at Guam; however, birds at Tinian show intermediate measurements.
At Guam, the starling is the most numerous land bird. The writer (1947b:124) , in counting birds along the roadways of Guam, recorded the starling on all of the 125 counts and found the birds to include more than one-half (57.3 percent) of all the birds seen. Starlings may have increased during the years of the war, with the disruption of normal agricultural activities allowing the growth of papaya and other food plants in fallow areas ”

“ Measurements have given evidence of the degrees of structural resemblance of the White Terns of the different islands, but it is not certain that the groupings made on this basis are natural; more data is needed on ecology and life history. Of particular importance is to learn whether these birds fly regularly from island to island. On the basis of eleven months of rather continuous observation in Micronesia, I suspect that the White Tern has little tendency to make inter-island migrations. ”

“ However, Mayr (1942b:236) includes the development of questionable and unusual kinds of insular forms in a general statement: "The potentiality for rapid divergent evolution in small populations explains also why we have on islands so many dwarf or giant races, or races with peculiar color characters (albinism, melanism) , or with peculiar structure (long bills in birds) , or other peculiar characters (loss of male plumage in birds) ."
Nutrition may be also a factor influencing speciation in bird life. The types of food plants (coconut, papaya, breadfruit, pandanus, etc.) ”

“ Where the layer of humus is deep, the fertility is greatest. Coralline-volcanic soils occur on some "high" islands where coral rock and volcanic rock have become mixed in the decomposition process which forms soil. In parts of the Marianas and elsewhere, unwise practices of burning and overgrazing have allowed extensive erosion to occur, resulting in reduced fertility of the soil. On the island of Yap certain sedimentary rocks are exposed which are thought to have been elevated from the ocean bottom. ”

“ The ability of the shore birds to migrate almost as well over water as over land may explain their spread into Oceania. The likelihood that shore birds, when migrating may have ventured to Micronesia and Polynesia initially from the Asiatic side of the Pacific is strongly suggested by the data given in the paragraph above. Also, on the Asiatic side of the Pacific there are large numbers of islands, which form several archipelagoes extending from Kamchatka south to Malaysia. ”

“ Two birds in Micronesia, the Kusaie Rail (Aphanolimnas) and the Kusaie Mountain Starling (Aplonis corvinus) , are known to be either extinct or so rare that they have not been taken since the time of Kittlitz, who visited the island of Kusaie in December, 1827, and January, 1828. Other birds (Anas oustaleti, Caloenas nicobarica, Megapodius l. lapérouse, and Metabolus rugensis) have become reduced in numbers and may be threatened with extermination. ”

“ The Reef Heron is a conspicuous member of the bird life of Micronesia, being recorded from most of the island groups. It prefers the placid and shallow waters of the lagoons and tidal beaches where it obtains the littoral animal life as food. The birds are seldom seen inland and usually frequent the beaches and rocky coasts. ”

“ Whether the genus and species evolved in the Atlantic or in the Pacific region is not known. If it were the Pacific region, the center of differentiation may very well have been the islands of Oceania. There, relatively little variation is observable within populations covering a large area. To the eastward, birds along the American coast are darker or lighter, to the northward, the birds of Hawaii are paler, to the southward and southwestward, the birds are smaller and to the westward, the birds are smaller and darker. ”

“ Guam has the largest land surface of any of the islands of Micronesia with 225 square miles, Ponapé has 145 square miles, and Babelthuap has 143 square miles. Asuncion, in the northern Marianas, has the highest elevation, rising as an almost perfect cone to a height of 2,923 feet; Ponapé reaches a height of 2,579 feet above the sea level. The volcanic islands are known as "high" islands, and the coral atolls are known as "low" islands. The coral islands usually rise but a few feet above sea level. ”