_Anas oustaleti_ Salvadori, Bull. British Ornith. Club, 4, 1894, p.
1. (Type locality, Mariannis Islands.)
_Anas oustaleti_ Salvadori, Cat. Birds British Mus., 27, 1895, p.
189 (Guaham); Oustalet, Nouv. Arch. Mus. Hist. Nat. Paris, (3), 8,
1896, p. 49 (Guam); Hartert, Novit. Zool., 5, 1898, p. 66 (Guam,
Saipan); Wheeler, Report Island of Guam, 1900, p. 13 (Guam);
Seale, Occ. Papers Bernice P. Bishop Mus., 1, 1901, p. 25 (Guam,
Saipan); Matschie, Journ. f. Ornith., 1901, pp. 110, 113 (Guam,
Saipan); Safford, Osprey, 1902, p. 66 (Mariannas); _idem_, Amer.
Anthro., 4, 1902, p. 711 (Guam); _idem_, The Plant World, 7, 1904,
p. 267 (Guam); Dubois, Syn. Avium, 2, 1904, p. 990 (Mariannes);
Safford, Contr. U. S. Nat. Herb., 9, 1905, pp. 80, 126 (Guam);
Prowazek, Die deutschen Marianen, 1913, pp. 47, 100 (Marianen);
Cox, Island of Guam, 1917, p. 22 (Guam); Phillips, Nat. Hist.
Ducks, 2, 1923, p. 53 (Guam, Saipan); Mathews, Syst. Avium
Australasianarum, 1, 1927, p. 214 (Guam, Saipan); Berlioz, Bull.
Mus. Hist. Nat. Paris, 2d ser., 1, 1929, p. 67 (Guam); Peters,
Check-list Birds World, 1, 1931, p. 159 (Guam, Tinian, Saipan);
Hand-list Japanese Birds, rev., 1932, p. 184 (Guam, Tinian,
Saipan); Bryan, Guam Rec., vol. 13, no. 2, 1936, p. 15 (Guam);
Kuroda, Tori, 11, 1941-42, pp. 99, 443 (Marianas); Hand-list
Japanese Birds, 3d ed., 1942, p. 205 (Guam, Tinian, Saipan);
Amadon, Amer. Mus. Novit., no. 1237, 1943, p. 1 (Marianne); Mayr,
Birds Southwest Pacific, 1945, p. 285 (Marianas); _idem_, Audubon
Mag., 47, 1945, p. 282 (Marianas); Baker, Trans. 11th N. Amer.
Wildlife Conf., 1946, p. 208 (Guam); Stott, Auk. 64, 1947, p. 525
(Saipan); Baker, Smithson, Misc. Coll., vol. 107, no. 15, 1948, p.
45 (Saipan, Tinian); Momiyama, Pacific Science, 2, 1948, p. 121
(Saipan, Tinian, Guam).
_Polionetta oustaleti_ Kuroda, in Momiyama, Birds Micronesia,
1922, p. 39 (Guam, Saipan).
_Anas superciliosa oustaleti_ Hartert, Novit. Zool., 36, 1930, p.
112 (Guam, Saipan).
_Anas platyrhynchos oustaleti_ Delacour and Mayr, Wilson Bull.,
57, 1945, pp. 21, 39 (Marianas).
_Geographic range._--Micronesia: Mariana Islands--Guam, Tinian,
Saipan.
_Characters._--From study of a large series of specimens of _Anas
oustaleti_, Yamashina (1948) described two types of plumages: one
type resembles that of _A. platyrhynchos_ and another type
resembles that of _A. poecilorhyncha_. He based his conclusions on
both a study of prepared skins and observations of the molt of
living specimens as reported by Kuroda (1941-1942). The following
descriptions are quoted from Yamashina (1948:122).
Adult male in nuptial plumage of _A. platyrhynchos_ type: "Whole
head is dark green, except at the sides where buff feathers are
plentifully intermingled, a dark brown streak through the eye, and
faint white ring on the lower neck. Feathers on scapulars and sides
of body are as those of _Anas poecilorhyncha_. Sides of body are
vermiculated but some brown feathers are found even in the full
nuptial plumage. Upper breast is dark reddish chestnut with dusky
spots. Upper and under tail-coverts are as in _Anas platyrhynchos_.
Speculum is as that of _Anas platyrhynchos_, but the tips of the
greater coverts are buff instead of white. Central tail feathers
are more or less curled upward. Base of bill is black, tip is olive
color. Iris is dark brown. Feet, reddish-orange, webs darker."
Eclipse plumage of adult male resembles that of _A. platyrhynchos_.
Adult male in nuptial plumage of _A. poecilorhyncha_ type:
"Resembles _Anas poecilorhyncha pelewensis_ from the Palau Islands
and Truk Island, but sides of head are browner, superciliary
stripes and ground color of cheeks are more buffy. Feathers on
upper breast and sides of body are more broadly edged with brown.
Speculum is usually violet-purple as in the _platyrhynchos_ type,
but in two specimens from Saipan and Tinian, respectively, it is
dark green as in _Anas poecilorhyncha pelewensis_. Tips of the
secondaries are usually white, but sometimes very faint as in
_Anas poecilorhyncha pelewensis_, and in one specimen from Saipan
they are buffy. Bill is olive color with a black spot in the
center of the upper mandible. Iris, dark brown. Feet, dark orange,
darker in joints and webs." Eclipse plumage of adult male
resembles the nuptial plumage.
_Measurements._--Measurements of nine ducks from Guam and Saipan
are: wing, 238-266 (252); tail, 75-84 (81); exposed culmen, 49-53
(51); tarsus, 41-43 (42).
_Specimens examined._--Total number, 9 (5 males, 2 females, 2
unsexed), as follows: Mariana Islands, USNM--Saipan, 2 (Oct. 2,
3)--Guam, 1 (June 6); AMNH--Saipan, 2 (Aug. 7, 11)--Guam, 4 (Jan.
10, April 6, Dec. 11, 16).
_Nesting._--At Guam, Seale (1901:25) found nests of the Marianas
Mallard "among the reedy swamps and streams of the island." He
obtained two downy young in June. Kuroda (1941-1942) reports
nesting at Lake Challankanoa, Saipan, in July. He writes that nests
contained 7 to 12 eggs. Ducklings and incubated eggs were obtained
in June and July, but he is of the opinion that the breeding season
may be longer. He notes that adults exhibit both nuptial plumage
and eclipse plumage at the same time, suggesting that breeding may
occur at various times in the year. A nest with seven eggs taken on
July 4, 1941, at Hagoi Lake, Tinian, is described by Kuroda as
having been found among rushes and constructed of dead leaves,
stems, and roots and lined with down. He describes the eggs as
being grayish-white with a pale greenish tinge, and measuring 61.6
by 38.9. Marshall (1949:202) saw a family of ducklings in April.
_Remarks._--The Marianas Mallard is rare; probably it never has been
very abundant in the small chain of islands to which it is restricted,
because fresh water marshes and swamps are not extensive. The bird was
first recorded by Bonaparte as _Anas boschas a. Freycineti_ in 1865.
This name was a _nomen nudum_ and later the same specimen in the Paris
Museum was named by Salvadori (1894) as _Anas oustaleti_. In 1888,
Marche obtained six specimens at Guam; these were reported on by
Oustalet (1896:49). Later collecting showed that the duck inhabited
also the islands of Saipan and Tinian. There have been no records of
this duck in the more northern islands of the Marianas. According to
Yamashina (1948:121) in the period from 1931 to 1940, the Japanese
obtained 38 specimens of the Marianas Mallard at Tinian and Saipan. In
1940, four birds from Tinian were shipped alive to Japan and kept in an
aviary by Kuroda. At Tinian in 1940, one of the collectors observed two
flocks of _A. oustaleti_, each containing 50 or 60 individuals. The
Japanese took specimens at a lagoon area and at fresh water lakes.
Yamashina describes one of the localities, Lake Hagoi on Tinian, as "a
small body of fresh water surrounded by about 40 acres of marsh." During
the war, servicemen reported the presence of the Marianas Mallard at
both Saipan and Tinian. Moran (1946:261) counted twelve ducks at Saipan.
Stott (1947:525) saw seven birds at Lake Susupe on Saipan in December,
1945. He writes that the birds were gentle and easily approached and
that they preferred winding channels in reed beds to open water.
Marshall obtained two ducks at Lake Susupe in early October, 1945. These
specimens are in the United States National Museum. He (1949:202) found
ducks at both Saipan and Tinian; twelve was the greatest number seen at
any one time. Gleise (1945:220) estimated that there were twelve birds
on Tinian in 1945, remarking that their habitat was swamp area.
At Guam and Rota, the NAMRU2 party failed to obtain any specimens but
received reports of the presence of ducks on both islands. At Guam,
reports were obtained of ducks of unknown species at a fallow rice paddy
in August, 1944, and in a marsh near Agat on June 13, 1945. The presence
of Japanese soldiers in the interior of Guam made it inadvisable to
investigate marshes and swamps of the interior and the upper courses of
streams. H. G. Hornbostel, as quoted by Phillips (1923:54), reported
that ducks were found at Guam only in the Tolofofo River Valley. The
NAMRU2 field parties investigated the lower reaches of this valley and
found no evidence of the ducks. The upper part of this valley was used
as an artillery range in 1945. Probably the firing of field guns was a
disturbing influence to any birds that might have been there. If the
ducks were on Guam at that time, they must have been secretive and
restricted in their movements. At Rota, two ducks which might have been
_A. oustaleti_ were seen by the NAMRU2 party on October 20, 1945, in a
cultivated field.
These recent reports indicate that the Marianas Mallard is secure for
the present on the islands of Saipan and Tinian, but thoughtful
conservation practices need to be placed in operation to insure its
survival in the future.
_Evolutionary history of Anas oustaleti._--In the past, most of the
studies have pointed to a northern ancestry for _A. oustaleti_. Bryan
(1941:187) has noted a relationship between _A. oustaleti_ and the
Laysan Duck (_A. laysanensis_ Rothschild) and the Hawaiian Duck (_A.
wyvilliana_ Sclater). Amadon (1943:1) suggests that these three species
of ducks are rather recent derivatives of the Common Mallard (_A.
platyrhynchos_) and postulates the evolution of _A. wyvilliana_ from
migrants from North America. He further states that _A. laysanensis_ and
_A. oustaleti_ may have been derived from _A. wyvilliana_ or may
represent independent colonizations. Delacour and Mayr (1945:21) go a
step further and make these forms subspecies of _A. platyrhynchos_,
saying that they are "dull-colored editions" of the Common Mallard, that
because of isolation they have become reduced in size and have lost many
of the characteristics of their ancestors. Recently, however, Yamashina
(1948) has concluded that the Marianas Mallard has evolved as the result
of hybridization between the two species, _A. platyrhynchos_ and _A.
poecilorhyncha_. His conclusions are based on a study of a large number
of specimens, both museum skins and captive birds, in which he has been
able to detect plumages of the _A. platyrhynchos_ type and of the _A.
poecilorhyncha_ type (see Characters). He has noted specimens which have
ninety percent of the characteristics of _A. platyrhynchos_ and ten
percent of the _A. poecilorhyncha_ type. These percentages are reversed
in specimens favoring the _A. poecilorhyncha_ type. In his series of
skins he finds the _A. poecilorhyncha_ type of plumage most frequently,
in forty-four specimens out of fifty examined, while only six specimens
have the _A. platyrhynchos_ type of plumage. Yamashina cites also as
evidence favoring his conclusion that hybridization has taken place the
results obtained from the crossing of captive _A. platyrhynchos_ and _A.
poecilorhyncha_. It is his assumption that there has been a resident
form of _A. poecilorhyncha_ in the Marianas, apparently resembling
closely that which occurs in the Palaus and at Truk (_A. p.
pelewensis_), and that stragglers of _A. platyrhynchos_ from the north
occasionally reach the Marianas where hybridization between the two
species occurs. Yamashina remarks (1948:123): "The opportunity for
hybridization should occur more rarely in the south, and thus more
frequent back-crossing of the hybrid with the indigenous _Anas
poecilorhyncha_ on Tinian and Guam explains the superabundance there of
the _poecilorhyncha_ type. As the hybridization should have taken place
more frequently to the north in Saipan, the ratio of the occurrence of
the _platyrhynchos_ type is logically higher there." The Common Mallard
(_A. p. platyrhynchos_) has not been recorded in Micronesia, but
according to Yamashina (1948:123) "winters frequently just north of the
Marianas in the Bonin and Volcano Islands."
This remarkable explanation for the development of the Marianas Mallard
is not questioned by this author, who feels that hybridization may be
found to be the cause for other unusual forms of life in island habitats
whose ancestry has not been explained. As Yamashina comments, the
special environments of islands together with small and restricted
populations of animals are factors which could favor such development.
=Anas poecilorhyncha pelewensis= Hartlaub and Finsch