Monarcharses geoffroyii Mathews, Bull. British Ornith. Club, 45, 1925, p. 94 (new generic name); idem, Syst. Avium Australasianarum, 2, 1930, p. 514 (Yap).
Monarcharses godeffroyi Takatsukasa and Yamashina, Dobutsu. Zasshi, 43, 1931, p. 486 (Yap?).
Geographic range.—Micronesia: Caroline Islands—Yap.
Characters.—Adult male: according to Sharpe (1879:432). "General colour above white, from the hind neck to the rump and including scapulars; wings black, the quills browner; upper tail-coverts and tail black; head all around black, including the lower throat; sides of neck and rest of under surface, from the foreneck downwards, pure white; thighs and under tail-coverts black; under wing-coverts black, quills ashy blackish below; white along the inner edge of the primaries; 'bill entirely blue; feet whitish blue; iris black' (Kubary M. S.)."
Adult female: "Entirely black, excepting the hind neck and upper mantle, sides of neck, lower throat, and fore neck, which are pure white" (Sharpe, 1879:432).
Immature: "Above brown, the head and hind neck ashy grey, the scapulars rufescent at the tips, the rump rufous, becoming paler and more fulvous on the upper tail-coverts; wing-coverts dusky brown, broadly edged externally with rufous-buff, becoming fulvous on the median and greater coverts; quills dark brown, externally edged with rufous, the primaries narrowly, the secondaries more broadly, the innermost of the latter edged and tipped with buff; tail-feathers ashy brown, narrowly edged with ochraceous brown and tipped with white, more broadly on the outer feathers; lores and a broad eyebrow rufous-buff; ear-coverts rather deeper rufous, shading on to the sides of the throat; under surface of body light cinnamon-rufous inclining to rufous on the throat and under tail-coverts; under wing-coverts light cinnamon, like the breast; quills light brown below, whitish along the inner web; 'bill horn-colour, the point brown, under mandible paler, feet dirty white, iris black' (Kubary M. S.)." (Sharpe, 1879:433).
Remarks.—No specimens of this species have been seen by me. Most taxonomists have regarded this bird as a member of the genus Monarcha, although Mathews did propose the name Monarcharses for this bird. On the basis of descriptions and pictures (especially plate 38 in Hartlaub, 1868:828) the bird appears to be related to the monarch flycatchers of the Melanesian area. It may be closest to Monarcha menckei from the Bismarcks, M. manadensis of the New Guinea region, M. barbatus from the Solomons or to M. leucurus from Buru. The drab color of the immatures and the black and white color of the adults are characteristics of the Yap Monarch which are shared with some of the other species of Monarcha. The connection between M. godeffroyi and Metabolus rugensis of Truk is not known, but they evidently represent separate colonizations. M. takatsukasae of Tinian appears to be an offshoot of M. godeffroyi of Yap, in which the black and white plumage has been suppressed (or never developed). As indicated by the published descriptions, the immature of M. godeffroyi shows a close resemblance to the adult of M. takatsukasae. The latter also shows relationships to immature specimens of M. leucotis and to M. guttula of Melanesia.
The relationship of the two species of Monarcha in Micronesia to the Hawaiian Flycatcher, Chasiempsis sandwichensis is not known. It is apparent that this Hawaiian form was derived from some ancestor from Melanesia, which arrived in the Hawaiian Islands by way of either Polynesia or Micronesia. Mayr (1943:45) has already pointed out that Chasiempsis is "related to the Monarcha group (Pomarea, Mayrornis, etc.)."