320 
Recently published Ornithological Works. [Ibis, 
32,800 birds listed in a census made in 1916, some 31,200 
have their homes and breeding-grounds. 
Far the most numerous in individuals are the Sooty Tern 
(.Sterna fuscata) and the Noddy (Anous stolidus) ; others of 
less importance as regards numbers are the Least Tern 
(Sterna a. antillarum ), the Roseate (S. dougalli), the Man- 
o^-War Bird (Fregata magmficens rothschildi ), and the 
Boobies (Sula leucogastris and S. sula), but the last three 
do not nest. 
Good accounts of all these species are given by 
Dr. Bartsch in the present paper, which is illustrated 
by a large number of photographs. There is also an 
interesting list of all the birds which have been recorded 
from the islands, as well as of the land-birds which have 
been observed there on different occasions on migration. 
Chapman on variation in Ostinops decumanus. 
[Unusual types of apparent geographic variation in colour and of 
individual variation in size exhibited by Ostinops decumanus. By Frank 
M. Chapman. Proc. Biol. Soc. Washington, vol. xxxiii. 1920, pp. 25-32.] 
Mr. Chapman has recently examined a large series of 
examples of Ostinops decumanus, chiefly from southern Peru 
and Bolivia, and also from Matto Grosso in south-west 
Brazil, and he finds among these birds, both male and 
female, a remarkable phenomenon of a varying number of 
feathers of the body and wing-coverts being wholly or in 
part yellow or more rarely white. Such a variation, if 
found in a single individual, would certainly be considered 
as pathological albinism or xanthochroism. But this curious 
variation is found to a variable extent in so large a propor¬ 
tion of the birds examined that it must be considered a 
diagnostic character, and to draw attention to it Mr. Chapman 
proposes to distinguish this form as a distinct subspecies, 
Ostinops decumanus maculosus. In birds from north of the 
Amazon valley this variation does not occur. 
In regard to size, Mr. Chapman finds a very remark¬ 
able variation among the males only—both those from 
the northern and southern parts of South America. 
