Erythrura trichroa claraTakatsukasa and Yamashina

*Kuroda (1922:28).

Coultas observed the finch at Kusaie in 1931; he wrote (field notes) that it is a common bird but difficult to obtain. He found it in most parts of the island and at all elevations; the bird appeared to prefer dense underbrush of the jungle or marginal vegetation. He found no evidence of breeding activity in February, March or April.

Erythrura trichroa claraTakatsukasa and Yamashina, Tori, 7, 1931, p. 110. (Type locality, Ruk Island.)

Erythrura trichroaFinsch (part), Journ. f. Ornith., 1880, p. 290 (Ponapé, Hügeln = Truk);idem, Proc. Zool. Soc. London, 1880, p. 576 (Ruk);idem(part), Ibis, 1881, pp. 104, 110, 112, 115 (Ponapé); Schmeltz and Krause (part), Ethnogr. Abth. Mus. Godeffroy, 1881, p. 353 (Ruk); Salvadori (part), Ornith. Papuasia, 2, 1881, p. 442 (Ponapé); Sclater (part), Ibis, 1881, p. 545 (Ponapé, Ruk); Sharpe (part), Cat. Birds British Mus., 13, 1890, p. 385 (Carolines = Truk, Ponapé); Wiglesworth (part), Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 42 (Ponapé, Ruk); Nehrkorn, Kat. Eiers, 1899, p. 122 (Ruk); Matschie (part), Journ. f. Ornith., 1901, p. 112 (Ruk, Ponapé); Dubois (part), Syn. Avium, 1, 1902, p. 583 (Carolines = Ponapé); Takatsukasa and Kuroda (part), Tori, 1, 1915, pp. 55, 64 (Ponapé); Mayr, Proc. 6th Pacific Sci. Congr., 4, 1941, p. 204 (Ponapé).

Erythrura trichroa trichroaHartert (part), Novit. Zool., 7, 1900, p. 6 (Ruk, Ponapé); Kuroda (part), in Momiyama, Birds Micronesia, 1922, pp. 27, 28, 29, 78 (Ponapé, Ruk); Mayr (part), Amer. Mus., Novit., no. 489, 1931, p. 4 (Ponapé, Ruk).

Chloromunia trichroaMathews, Birds Australia, 12, 1925, p. 208 (Ruk).

Chloromunia trichroa trichroaMathews (part), Syst. Avium Australasianarum, 2, 1930, p. 840 (Carolines = Truk, Ponapé).

Erythrura trichroa claraHand-list Japanese Birds, rev., 1932, p. 170 (Truk, Ponapé); Hand-list Japanese Birds, 3d ed., 1942, p. 189 (Truk, Ponapé); Mayr, Birds Southwest Pacific, 1945, p. 302 (Truk, Ponapé); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 74 (Truk).

Lobospingus trichroa claraMathews, Ibis, 1933, p. 96 (Ruk, Ponapé).

Geographic range.—Micronesia: Caroline Islands—Truk, Ponapé, Lukunor?

Characters.—Adult: Resembles adult ofE. t. trichroa, but slightly larger with underparts more yellowish and less greenish; blue on head slightly paler; sides of neck tinged more strongly with yellowish. Birds from Ponapé are slightly paler than those from Truk.

Measurements.—Measurements are listed intable 53. Birds from Ponapé and Truk differ but little in measurements.

Specimens examined.—Total number, 39 (22 males, 16 females, 1 unsexed), as follows: Caroline Islands, USNM—Truk, 2 (May 5, Dec.); AMNH—Truk, 15 (March, June, Nov.)—Ponapé, 22 (Dec.).

Molt.—Birds taken in March and June are not in molt. Some of the specimens obtained in November and December are in molt.

Remarks.—The differences betweenE. t. trichroaat Kusaie andE. t. claraat Ponapé and Truk are slight. Takatsukasa and Yamashina (1931d:110) separateE. t. clarafromE. t. trichroaof Kusaie on the basis of a paler blue coloring on head, body more yellowish green and sides of neck more distinctly golden-yellow.

Coultas obtained specimens at Ponapé in 1930 and reports (field notes) that the bird occurs in the extensive grassland areas of the island but that the numbers are small. He estimates the population to be less than 100 individuals. He learned that the Japanese had trapped them for shipment to Japan as caged birds. Coultas writes that the finch at Ponapé "is very shy and flies readily when he is disturbed. As soon as a call of alarm is uttered the whole flock flies up from the ground and heads for the true forest where they will hide. They will also work along in the grass, and make a getaway. The bird has a little hissing sybilation that it utters when on the wing." He found the bird in flocks of 3 to 20; immatures were frequently found alone.

McElroy of the NAMRU2 party obtained a female at Moen Island in the Truk Atoll in December, 1945. He found small flocks of these birds in dense vegetation along streams.

Erythrura trichroa pelewensisKuroda, in Momiyama, Birds Micronesia, 1922, p. 27. (Type locality, Pelew Islands).

Erythrura trichroa pelewensisKuroda, Ibis, 1927, p. 692 (Pelew); Mayr. Amer. Mus. Novit., no. 489, 1931, p. 4 (Pelew); Hand-list Japanese Birds, rev., 1932, p. 171 (Palau); Hand-list Japanese Birds, 3d ed., 1942, p. 189 (Babelthuap); Mayr, Birds Southwest Pacific, 1945, p. 301 (Palau).

Chloromunia trichroa pelewensisMathews, Syst. Avium Australasianarum, 2, 1930, p. 840 (Pelew).

Geographic range.—Micronesia: Palau Islands—Babelthuap.

Characters.—Kuroda (1922a:27) describes the bird as follows, "ResemblesE. trichroa(Kittlitz) from Carolines (the type from Kusaie), but distinguishable from it by the bill being much thicker and stouter, by the chin being tinged with blue, by the under-parts being paler throughout and somewhat tinged with bluish, by the rump and upper tail-coverts being bright crimson instead of dull crimson, by the central tail-feathers brownish red instead of dull crimson, by the distinct shafts of central tail-feathers and by longer wing and tail."

Measurements.—The measurements by Kuroda of a single specimen are listed intable 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 genusErythruraand placesE. trichroain the subgenusErythrura, noting thatE. t. cyaneifronsfrom Banks and the New Hebrides is similar to the subspecies found in Micronesia. As a group the subspecies ofE. trichroaare very similar, but the populations in Micronesia appear closest to subspecies from the Solomons, Admiralty Islands and possibly toE. t. modestafrom 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.

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

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

Donacola hunsteini minorMathews, Ibis, 1933, p. 95 (Ponapé).

Lonchura nigerrima minorMayr, 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 toM. hunsteinifrom 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 byYamashina 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.

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

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

Lonchura punctulata cabanisiYamashina, 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.

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 (seefigure 8).

2. Oceanic birds are among the oldest forms of bird life inhabitingMicronesia. 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 (seefigure 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 insularclimates, which appear to favor colonists from tropical homes rather than those from Palearctic homes.

7. The factors most important in the process of differentiation of birds in the islands of Micronesia are isolation, paucity in numbers of individuals, freedom from predation, absence (and presence) of interspecific and intraspecific strife, and nutrition. The importance of the "dilution" factor is discussed, and the possibility of cross-breeding between different kinds of birds is considered. It is concluded that genetic change altering the phenotypic expression of avian characteristics is no more apt to occur in insular populations than in continental populations, but such changes have a greater chance of being perpetuated in insular populations.

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