Part 126

Measurements.--The measurements by Kuroda of a single specimen are listed in table 53.

Remarks.--Only one specimen of this subspecies is known. The NAMRU2 party did not obtain any record of it in the southern Palaus in 1945. If still present in the islands, it may be confined to the higher forested areas of Babelthuap.

Evolutionary history of Erythrura trichroa in Micronesia.--The Blue-faced Parrot-finch has been recorded from Kusaie, Ponapé, Truk and Palau, which are all "high" islands of southern Micronesia. This bird belongs to a species which occurs in Melanesia, northern Australia, Celebes, and the Moluccas. Stresemann (1940:40) points out the interesting observation that this species ranges only east of Wallace's Line. Mayr (1931c:1-10) has reviewed the parrot-finches of the genus Erythrura and places E. trichroa in the subgenus Erythrura, noting that E. t. cyaneifrons from Banks and the New Hebrides is similar to the subspecies found in Micronesia. As a group the subspecies of E. trichroa are very similar, but the populations in Micronesia appear closest to subspecies from the Solomons, Admiralty Islands and possibly to E. t. modesta from the Moluccas, which appears to indicate that Micronesia was invaded from the south or from the southwest via the Moluccas. Whether the little known subspecies at Palau represents an independent invader from the Moluccas is uncertain.

=Lonchura nigerrima minor= (Yamashina)

Black-breasted Weaver-finch

Munia (Donacola) hunsteini minor Yamashina, in Takatsukasa and Yamashina, Dobutsu. Zasshi, 43, 1931, p. 600. (Type locality, Ponapé.)

Lonchura hunsteini minor Hand-list Japanese Birds, rev., 1932, p. 171 (Ponapé, Truk); Hand-list Japanese Birds, 3d ed., 1942, p. 190 (Ponapé, Truk).

Donacola hunsteini minor Mathews, Ibis, 1933, p. 95 (Ponapé).

Lonchura nigerrima minor Mayr, Birds Southwest Pacific, 1945, p. 301 (Ponapé, ?Truk).

Geographic range.--Micronesia: Caroline Islands--Ponapé, Truk?

Characters.--Yamashina in Takatsukasa and Yamashina (1931c:600) characterizes this subspecies as similar to M. hunsteini from New Ireland, but smaller; the wing of the adult of the bird from Ponapé is from 46 to 49 mm, instead of 50-51 mm. as in the New Ireland bird. Moreover the crown and nape are white instead of pearl gray.

Remarks.--Little is known concerning this subspecies named by Yamashina at Ponapé. No specimens have been seen by me. Richards obtained one male at Ponapé in 1947-1948. He found the birds in large flocks.

=Lonchura punctulata cabanisi= (Sharpe)

Philippine Nutmeg Mannikin

Munia cabanisi Sharpe, Cat. Birds British Mus., 13, 1890, p. 353. (Type locality, Luzon.)

Munia punctulata cabanisi Kuroda, in Momiyama, Birds Micronesia, 1922, p. 78 (Yap).

Lonchura punctulata cabanisi Yamashina, Tori, 7, 1932, p. 395 (Yap); Hand-list Japanese Birds, rev., 1932, p. 171 (Yap); Hand-list Japanese Birds, 3d ed., 1942, p. 189 (Yap).

Geographic range.--Philippine Islands and Micronesia. In Micronesia: Palau Islands; Caroline Islands--Yap.

Characters.--A small finch with upper parts light grayish-brown, feathers with white shafts producing a streaked appearance; lores, anterior part of auriculars, malar region, and feathers of chin and throat chocolate-brown with faint white shafts; breast and sides mottled white and dark brown, middle of abdomen and under tail-coverts pale buffy-white, wings brown with lighter edges, under wing dark with lighter coverts; upper tail-coverts and middle tail feathers dark olive, outer tail feathers colored like wings; bill heavy and black; feet dark brown.

Remarks.--The Philippine Nutmeg Mannikin is a resident on the island of Yap. Yamashina (1932a:395) records a nest containing one egg taken there on May 15, 1932. Marshall (1949:221) records this bird at Palau on November 6 and December 2, 1945. Whether this bird was introduced to Yap and Palau by man or whether it reached there by independent invasion is unknown.

SUMMARY AND CONCLUSION

The avifauna of Micronesia consists of 206 kinds of birds belonging to 37 families and 91 genera. Of these, 30 kinds are sea birds, 29 kinds are migratory shore birds, and 146 kinds are land and freshwater birds. Of the 30 sea birds, 18 kinds are resident; of the 147 land and fresh-water birds, 104 kinds are resident and 6 kinds have been introduced by man. There are no resident shore birds in Micronesia. The following conclusions can be drawn from this study:

1. The islands of Micronesia are oceanic islands and were seemingly formed independently of any present day continental land mass. Terrestrial organisms have reached these islands by "over-water dispersal." The avifauna of Micronesia has been received from the following sources: Polynesia, Melanesia, the Moluccas, Celebes, Phillipines, and Palearctica (see figure 8).

2. Oceanic birds are among the oldest forms of bird life inhabiting Micronesia. The presence of elevated islands containing phosphate, resulting from the deposition of guano by oceanic birds, is some indication of the length of time during which these birds have been present. In number of individuals, the oceanic birds inhabiting the inshore zone are more numerous than those inhabiting the offshore and pelagic zones, although twelve of the eighteen resident kinds of oceanic birds prefer the offshore and pelagic zones. Most of the species of oceanic birds resident in Micronesia are circumtropical in distribution; no residents are known in Micronesia which have been derived from Palearctica or the North Pacific. Micronesia has no endemic oceanic birds.

3. On the migratory flights, shore birds reach Micronesia along three distinct flyways, which in this report are named the Asiatic-Palauan Flyway, the Japanese-Marianan Flyway, and the Nearctic-Hawaiian Flyway (see figure 7). The shore birds began to utilize the Pacific islands as wintering grounds by gradually spreading from the Eastern Hemisphere rather than from the Western Hemisphere.

4. More than half (52 percent) of the land birds and fresh-water birds in Micronesia were derived directly from ancestral stocks in Melanesia. 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. The Marshall Islands may be regarded as a part of the Polynesian Subregion from the viewpoint of avian zoogeography.

5. Endemism in the land birds and fresh-water birds of Micronesia is extreme. Of 104 native, resident birds, 97 (93.5 percent) have become differentiated and can be separated taxonomically from related forms. In Micronesia, there are 5 endemic genera, 31 endemic species, and 76 endemic subspecies. The families containing the greatest number of endemic forms are Muscicapidae (14), Zosteropidae (14), Columbidae (13), and Sturnidae (9).

6. It is concluded that some of the more important factors controlling the dispersal of the bird life to Micronesia are the direction and the intensity of the winds, the small size of the islands, the isolation of the islands (especially those "high" islands), and the insular climates, which appear to favor colonists from tropical homes rather than those from Palearctic homes.