========================+=====+========+=======+===========+===========
LOCALITY | No. | Wing | Tail | Culmen | Tarsus
------------------------+-----+--------+-------+-----------+-----------
_Poliolimnas cinereus | | | | |
collingwoodi_ | | | | |
Philippines, | 13 | 98 | | 22.5 | 38.0
Talaut. Celebes | | 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