Remarks.—In 1945 the NAMRU2 party found the Palau Fantail in small numbers at Peleliu, Garakayo and Ngabad. At Peleliu the birds were noted as singles or in pairs in brushy undergrowth in forested areas. The birds were observed also in the second growth vegetation in the battle areas. Coultas (field notes) found the bird to be rare and restricted to the true forest, when he visited the Palau Islands in 1931. 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. Oustalet (1896:70) notes a close relation between Rhipidura of the Marianas and R. rufifrons of Australia. Mayr (1941b:202, 203) regards the genus Rhipidura as typical of the Polynesian area and remarks that speciation within this genus has proceeded at a relatively rapid rate. Mayr and Moynihan (1946) have devoted a 21-page paper to a thorough discussion of the R. rufifrons group, based on the extensive collections at the American Museum of Natural History. They remark that no other genera are closely related to Rhipidura and that evolution has proceeded further in R. rufifrons than in any other species of the genus. These authors regard the Papuan area, probably New Guinea, as the original home of this group. From their study they point out that many of the subspecies of R. rufifrons of the Papuan area, especially those of the Louisiades and the Solomons, appear to be the least specialized of the species, and that this lack of specialization in these subspecies indicates that the ancestral stock of the species R. rufifrons acquired its specificity somewhere in that area. With regard to the kinds of Rhipidura in Micronesia, Mayr and Moynihan (1946:fig. 2) have logically found three separate colonizations within the area: one represented today by R. lepida at Palau; one of subspecies of R. rufifrons at Yap and in the Marianas; and one by R. r. kubaryi at Ponapé.
R. lepida, according to Mayr and Moynihan (1946), is a result of an early colonization by Rhipidura. It is related to R. dedemi, R. superflua, and R. teijsmanni, which are mostly monotypic or have only two or three subspecies within the species. These three species are found in the region including Celebes and the Moluccas. R. lepida apparently invaded the Palau Islands from Celebes or an adjacent area and, among named species, most closely resembles R. teijsmanni. Both of these species have a white chin and throat, black breast patch, and rufous abdomen. R. lepida has become differentiated chiefly by the presence of a rufous head and back, a more distinct breast band, and proportionately different amounts of rufous and black coloration of the tail feathers.
Mayr and Moynihan (1946:6) give as the chief characters of R. rufifrons the following: "a rufous forehead, a grayish brown head and upper back, a well-defined rufous rump, a white chin and throat, a black breast band with scaling at its lower edge, and a dark brown tail with a distinct rufous base and a white tip." The Micronesian subspecies of R. rufifrons at Yap and in the Marianas display these characters. Of the four subspecies found in the area including Yap and the Marianas, R. r. versicolor, R. r. saipanensis, R. r. mariae and R. r. uraniae, the two first named most closely approach the ancestral stock, which may have been R. r. commoda Hartert of the northern Solomons or some near relative in Melanesia. The amount of white on the chin and throat and on the malar stripe, in R. r. versicolor and R. r. saipanensis is probably nearer that which obtained in the ancestor. At Rota, R. r. mariae, exhibits less white on the throat and a thinner, white malar stripe, while at Guam, R. r. uraniae possesses only a small amount of white on the chin and only a very thin line of white in the malar region. This variation in coloration suggests that the birds may have originally become established at Yap, Saipan and Tinian and later, birds from Saipan and Tinian spread to Rota and lastly to Guam.
R. r. kubaryi of Ponapé, although considered as a subspecies of R. rufifrons by most workers, has lost the rufous coloring found in most members of the species. Mayr and Moynihan (1946:6) point to its evolution through subspecies in the Santa Cruz Islands, where in R. r. agilis Mayr the rufous of the lower back is restricted to the upper tail-coverts, and in R. r. melanolaema Sharpe and R. r. utupuae Mayr the rufous is absent. In the latter two subspecies, as well as in R. r. kubaryi, the forehead is white instead of rufous.
The invasion of Micronesia by Rhipidura has undoubtedly been the result of abnormally long flights by a relatively weak flyer. The fact that Rhipidura has succeeded in establishing itself at only a few of the seemingly suitable islands in Micronesia may indicate that the possibilities for chance migration and resulting colonization are small, but that new colonization may be expected in the future.
It is my opinion that the populations of Rhipidura, as I have observed them in Micronesia, are small because each individual or pair of birds is dependent on a relatively large area of woodland to satisfy its habitat requirements, especially for food. This suggestion needs to be tested by observation made in the field. In comparison with the insect fauna of New Guinea or some other large island, that of Micronesia is indeed small in number of kinds. Hesse, Allee and Schmidt (1937:524) explain the absence of insectivorous animals such as "swallows, swifts, flycatchers, and insectivorous bats" in island communities on the basis of the small number of flying insects in these communities. Probably Rhipidura is able to forage for sedentary insect life as well as for the flying forms.
Metabolus rugensis (Hombron and Jacquinot)
Truk Monarch
Muscicapa Rugensis Hombron and Jacquinot, Ann. Sci. Nat. Paris, (2), 16, 1841, p. 312. (Type locality, Roug = Truk.)