Table 17. Measurements of Three Subspecies of Poliolimnas cinereus
Table 17. Measurements of Three Subspecies of Poliolimnas cinereus
| Location | No. | Wing | Tail | Full culmen | Tarsus |
| Poliolimnas cinereus collingwoodi Philippines, Talaut. Celebes | 13 | 98 | 22.5 | 38.0 | |
| 92-108 | 21.0-24.0 | 35.0-41.0 | |||
| Poliolimnas cinereus micronesiae Guam | 10 | 95 | 51 | 21.0 | 37.0 |
| 91-102 | 50-53 | 20.0-22.5 | 34.5-39.0 | ||
| Palau | 10 | 93 | 51 | 21.0 | 37.0 |
| 89-95 | 51-53 | 20.0-23.0 | 34.0-38.0 | ||
| Truk | 5 | 95 | 51 | 21.0 | 36.0 |
| 94-97 | 51-53 | 20.5-22.5 | 35.0-37.0 | ||
| Poliolimnas cinereus brevipes S. Dionisio Island | 8 | 96 | 19.0 | 30.0 | |
| 94-97 | 17.0-20.0 | 29.0-32.0 |
Specimens examined.—Total number, 25 (11 males, 13 females, 1 unsexed), as follows: Mariana Islands, AMNH—Guam, 10 (July 13, Aug. 1, 5, 7, 13, 19, 23, 31); Palau Islands, AMNH—exact locality not given, 10 (Nov. 11, 13, 15, 23, 25); Caroline Islands, AMNH—Truk, 5 (June 3, 8, 16, 17, 18).
Nesting.—Hartert (1900:9) describes two nests found on swampy ground. One contained three eggs, the other four eggs. He writes, "The eggs are pale buff, or cream-colour, speckled all over with brownish rufous, more frequently near the broad end. In some eggs, these spots are larger, in others minute, and there are often some, underlying pale purplish gray spots."
Remarks.—Superficially, the White-browned Rail of Micronesia is distinct from its near relative, P. c. collingwoodi, but the differences are not so well marked as they are between insular populations of other species of rails. It is probably a comparatively recent addition to the Micronesian avifauna, and its pattern of distribution may represent an early stage in the development of endemism in contrast to the pattern of later stages in the development of insular forms shown by the isolated rails, Rallus owstoni and Aphanolimnas monasa. The fact that Poliolimnas cinereus is found only on widely separated islands in Micronesia does not necessarily mean that it has become "extinct" on the intervening islands, but that it may be partial to the larger, "high" islands, or that it is actually present but remains to be discovered on these intervening islands when more intensive field investigations are made. Hachisuka (1939a:151), in naming the Micronesian form, comments that it has a shorter bill than P. c. collingwoodi of the Philippines and Celebes, and that it is intermediate between this subspecies and P. c. brevipes of the Volcano Island to the north. Within these three subspecies there are trends toward a shorter culmen and shorter tarsus and, less markedly, toward a shorter wing. From the evidence at hand, it can be concluded that Poliolimnas first colonized Micronesia probably from the Philippine area (or Papuan area) through the Palaus and Carolines, to the Marianas and north to the Volcano Islands. Further, this has probably been a relatively recent invasion, although the subspecies in the Volcano Islands shows marked change in length of tarsus and culmen. This extension of range to the islands north of the Marianas is unusual and resembles somewhat the distribution of Nycticorax caledonicus in the same general area.
The Micronesian White-browed Rail is a shy bird with the typical skulking habits of most rails. The NAMRU2 party did not find the bird at Guam, although reports were obtained that it was present in the marsh and swamp areas. Coultas (field notes) tells of observing the rail at Palau at a fresh water lake on Babelthuap, where it was difficult to obtain and apparently rare. Seale (1901:30) obtained a female specimen at Guam from native boys who snared it in a sweet potato patch near the Agaña River. This bird, taken in June or July, had eggs ready for laying. McElroy of the NAMRU2 party observed rails at Truk in brackish swamps, where he found them to be fairly common. A male which was taken in December had enlarged gonads. At Asor in the Ulithi Atoll, the NAMRU2 party learned that a small rail (possibly of this species) was found at taro patches in the early days of occupation, but that it was apparently eliminated by clearing operations. The taking of a bird at Bikini, as reported by Yamashina (1940:679), is further evidence that these birds may subsist on coral atolls as well as on the high volcanic islands; possibly the bird of the Marshalls may have been derived from the south rather than from the west. Unlike Rallus owstoni, this bird is apparently restricted to swampy areas, and may be eliminated from its habitat by drainage or clearing by man. It may always persist, however, in the taro patches maintained by the natives.
Gallinula chloropus subsp. near orientalis Horsfield
Gallinule
Gallinula orientalis Horsfield, Trans. Linn. Soc. London, 13, 1821, p. 195. (Type locality, Java.)