46 
ANAS WY VILLI ANA 
and then dealt at some length with the various differences found among the five specimens then at 
hand in the U.S. National Museum. Other remarks were made about this species by Salvador! 
(1895) who also considered this bird more or less of an ornithological puzzle. Rothschild (1900, 
p. 271) in the Avifauna of Laysan, gives two plates of Anas uyvilUana and discusses his large series 
of specimens. 
In the ten specimens now before me the main points of sexual difference are as follows. Of the 
six males, four are correctly sexed, one is not sexed, and one has been sexed both as a male and a 
female and then had both marks crossed out. There is, however, no question about the sex of either 
of these two. All six males present the characteristic V-shaped markings on the breast, thickly 
streaked throat and cheeks, nearly black pileum, sometimes mixed with iridescent green toward 
the neck, and except in one case evidence of sex-feathers in the tail. In this one case (U.S. National 
Museum, No. 113,448) the middle tail-feathers are lacking, probably moulted out, as the date is 
May. The sex-feathers appear to be typically three in number, but there may be four. They are not 
so well developed as in the Mallard. 
Of the four females all are correctly sexed. They all have the streaked under parts, immaculate 
throats and absence of sex-feathers. 
The table of measurements below shows the size difference in the two sexes. This is small and 
about comparable with that seen in Anas diazi. 
Males 
113,447 
U.S.N.M. 
113.449 
U.S.N.M. 
131.717 
U.S.N.M. 
113.448 
U.S.N.M. 
21,319 
U.S.N.M. 
15,025 
M.C.Z. 
Average 
Culmen 
44 
44 
45 
48 
44 
46 
45 
Wing 
230 
218 
223 
228 
218 
212 
221 
Tarsus 
37 
39 
39 
40 
39 
38 
39 
Females 
12.788 
U.S.N.M. 
Type of 
Anas aberii 
113,450 
U.S.N.M. 
131,718 
U.S.N.M. 
48,. 384 
M.C.Z. 
48,383 
M.C.Z. 
■Average 
Culmen 
42 
44 
41 
44 
45 
43 
Wing 
212 
210 
206 
215 
219 
212 
Tarsus 
35 
38 
38 
38 
41 
38 
We must now turn to Dr. Stejneger’s account of the species. He first describes the two males, 
U.S. National Museum No. 113,447 and No. 113,449, and shows several points of difference between 
them, especially in the color of the bill, in the anterior white wing-band and in the under wing- 
coverts and under tail-coverts. No. 113,448 was taken to be a female (absence of sex-feathers noted 
above) although the specimen is without doubt a male, as evidenced by the characteristic breast- 
pattern, large size, and dark chin. The smaller upper wing-coverts are broadly margined with cin- 
namon in this specimen, a character also seen especially well in No. 131,718 and in the type of 
Anas aherti. This certainly looks, as Stejneger himself suggests, like a youthful type of plumage, 
for the males of more advanced plumage show the small wing-coverts plain drab, slightly edged with 
white. 
Of the other two specimens described as females. No. 21,319 is a typical male, and this leads to a 
misunderstanding. The only female then which Dr. Stejneger had was No. 113,450. He mentions 
