1887.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 291 

 Subgenus Nannocnus Stejn. 



(va'vvoi, dwarf; oKvoi, bittern.) 

 (l:V2.) Ardetta eurhythma SwiNii. 



Schrenck's Little Bitteru. Yosbi-goi. 



1860. — Ardea cinnamom^a Schrenck, Reis. Amurl., I, p. 447, pi. xiii, fig. 3 {nee Gm^i.., 



1788). 

 1873. — Ardttta enrhi/thma Swinhoe, Ibis, 1873, p. 73. — hi., ibid., 187.5, pp. 132, 455. — 



Id., ibid., 1876, p. 335. — Blakist. & Pryer, Ibis, 1878, p. 2:^3. — /ifi., Trans. 



As. Soc. Jap. VIII, 1880, p. 199.— lid., ibid., X, 1^82, p. 118.— Blakist., 



Amend. List B. Jap., p. 12 (1884). 

 1873. — Ardetta eurythma Swinhoe, Ibis, 1873, pi. ii. 

 1874. — Ardetta sinensis Taczxviow SKI, Journ. f. Orn., 1874, p. 325 (nee Gmel. ). 



Schrenck's Little Bittern diifers from the Little Yellow Bittern not 

 only by the characters of structure and proportions already pointed 

 out, but also by the coloration of the upper parts, which is more or less 

 dark chestnut, uniform, or varied with whitish spots. 



The exact relations of the different plumages are not yet fully under- 

 stood, and a thorough study of these birds in the field is a very desira- 

 ble and promising one. How complicated the question is may be best 

 understood from a quotation of Mr. Swinhoe's observations on breed- 

 ing birds (Ibis, 1875, p. 133). 



On May 20 he obtained a "male with enormous testes," and on 

 the same date a female with the " eggs largely developed, nearly ready 

 for emission," but it had the ^^ plumage spotted lilie that of the immature 

 bird.^^ He continues as follows : " On the 21st a bird in the male dress 

 [unspotted] proved on dissection to be a female, and on the 22d one in 

 female dress [spotted] turned out to be a male. There was no difference 

 in the swollen state of their sexual organs from those of normal birds. 

 From the number of adult females I examined there can be no doubt 

 that the immature dress is the full feminine costume; and that an occa- 

 sional female, probably well advanced in years, should affect the male 

 plumage is a very ordinary circumstance amongst birds. But what 

 means the adult male in immature dress "? I presume that males re- 

 quire two years to acquire their full plumage, and breed in their first 

 year." Finally he adds (p. 134) : " I know no other Bittern of which 

 the sexes have different plumages." 



This last remark at once makes us think of the European Little Bit- 

 tern {Ardetta minuta) and the American Least Bittern {Ardetta exilis). 

 Nearly all the European authorities (including Dresser and Seebohm) 

 agree that in the former the sexes are very different, the male having 

 the back glossy greenish black, and the female dark Vandyke-brown, 

 like the adult Japanese Yellow Bittern. Naumann, however, asserts 

 most positively (Xaturgesch. Vog. Deutschl., IX, p. 201) that the old 

 female is black above like the male. But may it not be that Kaumanu 

 obtained female A. minuta in the plumage of the male just as Swinhoe 



