_Hypotaenidia owstoni_ Rothschild, Novit. Zool., 2, 1895, p. 481.
(Type locality, Guam.)
_?Rallus philippinus_ Gray, Cat. Birds Trop. Is. Pacific Ocean,
1859, p. 51 (Marian or Ladrone Is.).
_Rallus pectoralis_ Finsch and Hartlaub, Fauna Centralpolynesiens,
1867, p. 157 (Guam).
_Eulabeornis forsteri_ Gray (part), Hand-list Birds, 3, 1871, p.
57 (Marian).
_Hypotaenidia philippensis_ Pelzeln, Ibis, 1873, p. 41 (Marianne
Isl.); Salvadori (part), Ornith. Papuasia, 3, 1882, p. 261
(Marianas); Sharpe (part), Cat. Birds British Mus., 23, 1894, p.
39 (Guam).
_Rallus philippinus_ Wiglesworth (part), Abhandl. und Ber. Zool.
Mus. Dresden, no. 6, 1890-1891 (1891), p. 59 (Guam).
_Hypotaenidia owstoni_ Hartert, Novit. Zool., 5, 1898, p. 62
(Guam); Safford, Osprey, 1902, pp. 41, 67 (Guam); _idem_, The
Plant World, 7, 1904, p. 265 (Guam); Dubois, Syn. Avium, 2, 1904,
p. 961 (Mariannes); Safford, Contr. U. S. Nat. Herb., 9, 1905, p.
79 (Guam); Cox, Island of Guam, 1917, p. 21 (Guam); Kuroda, in
Momiyama, Birds Micronesia, 1922, p. 42 (Guam); Hartert, Novit.
Zool., 34, 1927, p. 22 (Guam); Mathews, Syst. Avium
Australasianarum, 1, 1927, p. 84 (Guam); Hand-list Japanese Birds,
rev., 1932, p. 196 (Guam).
_Hypotaenidia marchei_ Oustalet, Nouv. Arch. Mus. Hist. Nat.,
Paris, (3), 8, 1896, p. 32 (Type locality, Guam).
_Hypotaenidia oustini_ Seale, Occ. Papers Bernice P. Bishop Mus.,
1, 1901, p. 30 (Guam).
_Rallus owstoni_ Peters, Check-list Birds World, 2, 1934, p. 166
(Guam); Bryan, Guam Rec., vol. 13, no. 2, 1936, p. 15 (Guam);
Hand-list Japanese Birds, 3d ed., 1942, p. 220 (Guam); Mayr, Birds
Southwest Pacific, 1945, p. 287 (Guam); _idem_, Audubon Mag., 47,
1945, p. 279 (Guam); Watson, Raven, 17, 1946, p. 41 (Guam);
Strophlet, Auk, 1946, p. 536 (Guam); Baker, Smithson. Misc. Coll.,
vol. 107, no. 15, 1948, p. 48 (Guam).
_Geographic range._--Micronesia: Mariana Islands--Guam.
_Characters._--Adult: A large rail with head, neck, and eye stripe
near "mummy brown" with feathers on sides of neck tipped with
"russet"; superciliary stripe to back of neck, throat and upper
breast near "mouse gray"; mantle, back, scapulars, and some upper
wing-coverts dark olive-brown becoming browner on rump and upper
tail-coverts; wings dark with brownish spots and barred with
white; lower breast, abdomen, under tail-coverts, and tail
blackish with white barrings; bill lead colored; feet dark brown;
tibia brown; iris red.
_Measurements._--Four adult males measure: wing, 120-123 (121);
tail, 46-54 (50); full culmen, 37-43 (41); tarsus, 47-51 (50); six
adult females measure: wing, 108-118 (112); tail, 38-46 (42); full
culmen, 36-39 (37); tarsus, 43-47 (45).
_Weights._--The NAMRU2 party obtained specimens with the following
weights: two adult males 256, 257; four females 147, 153, 210, 252
grams.
_Specimens examined._--Total number, 13 (5 males, 6 females, 2
unsexed), from Mariana Islands, USNM--Guam (Jan. 29, May 8, June
19, 20, 23, 28, 30, July 14, 19, 23, Sept. 8).
_Nesting._--A nest was found by McElroy of the NAMRU2 party at Guam
on October 24, 1945, in dense grass on a hillside near Mount Santa
Rosa. The nest contained three eggs, which the author (1948:48)
describes as "white with a pinkish cast and a scattering of small
spots of colors near 'russet' and near 'pear blue' which are
concentrated at the large ends. They measure 37.5 by 29.1, 39.1 by
28.0, and 40.7 by 29.0." Downey, black chicks were found on April
1, May 16, and May 26. M. Dale Arvey found a chick on August 2,
1946, near Tumon Bay. A parent bird with young ones was seen near
Merizo on October 2. A male taken on January 26 had enlarged
gonads. Seale (1901:30) obtained a black chick in June or July. On
the basis of the above observations it seems that the nesting
season extends from spring to fall, although Marshall (1949:219)
assumes that this rail breeds the year around.
_Remarks._--The Guam Rail was first reported by Quoy and Gaimard who
called it "Ralê tiklin," but was not described as new until 1895 by
Rothschild. It appears to be equally at home in upland grassy areas and
in jungle areas. The species was not seen frequently by the NAMRU2
party, although birds were occasionally observed crossing the roads. Few
birds were shot; most of the specimens were taken in rat traps, which
may be the most satisfactory method of obtaining them. Coultas took his
specimens with the aid of a dog. On June 19, 1945, a small patch of
woodland was being removed by a bulldozer. Four rails, which were hiding
in this thicket, were surrounded and three were captured by hand. These
birds tried to escape over the cleared ground by running with wings
flapping but made no effort to fly. I am inclined to believe, as the
natives do, that these birds are virtually incapable of actual flight.
The Guam Rail usually appeared to be a quiet bird, but at Tarague Point
on July 12, 1945, I heard its loud penetrating cry; it was a series of
rapid screeches. At the same time rapid movement made considerable noise
in the undercover. The bird making the call suddenly appeared, either
rapidly chasing, or being chased by, another rail. The birds had
abandoned their usual skulking habits and had little concern for the
observer. I took this to be breeding behavior, comparable to that of
some of the North American rails during the mating period.
The Guam Rail is probably not in serious danger of extermination. It is
utilized by the natives as food; they capture the bird, using dogs and
trail snares. Its skulking habits and ability to inhabit most types of
cover on the island should insure its existence for a long time to come.
_Evolutionary history._--_Rallus owstoni_ is endemic to the island of
Guam with no closely related forms nearby. It is one of the several
rails found in the Pacific which live on isolated islands. In comparison
with other species in the region, it has some resemblance to both _R.
torquatus_ and _R. philippensis_. In general, the underparts of _R.
owstoni_ resemble those of the _R. philippensis_ group, although the
upper parts resemble somewhat those of _R. torquatus_. Certain specimens
of _R. owstoni_ have a slight indication of a pale pectoral band. The
bill is shorter and heavier than that of _R. torquatus_, possibly more
like that of _R. philippensis_. The short rounded wing is a distinctive
character. The bird came from an ancestral stock possibly resembling _R.
philippensis_ and probably originated in the Philippine or Papuan areas.
It may have invaded Micronesia at an early date and may have had a wider
distribution in the islands in former times. Perhaps this same invasion
resulted in the establishment of _R. wakensis_ (Rothschild) at Wake. The
supposed route of colonization is shown in figure 9.
[Illustration: FIG. 9. Routes of dispersal of rails in the Pacific area.]
=Rallina fasciata= (Raffles)