Vol. XXX VII 



1919 



Oberholser, Notes on N. A. Birds. 557 



Scseophaethon rubricaudus rotshchildi (Mathews). 



The Red-tailed Tropic Bird is included in our North American 

 list on the basis of a single specimen obtained by Mr. A. W. An- 

 thony near Guadalupe Island, Lower California, on April 23, 1897. 1 

 We have recently examined this specimen, which is now No. 21822 

 in the collection of the Carnegie Museum of Pittsburgh, Pa., and 

 find it to belong to the subspecies Scccophcetho7i rubricaudus roths- 

 childi, recently described 2 from Laysan Island in the Hawaiian 

 group. This race differs from Scceophoetkon rubricaudus rubri- 

 caudus, from the region about the Island of Mauritius, in its shorter 

 bill and wing; and from Sccpophcethon rubricaudus norcehollandiae 

 (Brandt), from Australia, in its smaller size and paler, less rosy 

 coloration. By this change of identification the place of Scoeo- 

 phasthon rubricaudus rubricaudus in the North American list should 

 be taken by Scceophaethon rubricaudus rothschildi. 



Casmerodius albus egretta (Gmelin). 



The forms of the genus Casmerodius (= Herod ias 3 ) are com- 

 monly considered distinct species. Mr. G. M. Mathews has, 

 however, recently treated 4 the Australian bird as a subspecies. 

 So far as our material indicates, there are, as Dr. R. B. Sharpe 

 concludes, 5 three forms of the genus, but all are without doubt 

 only subspecies. The principal characters separating these con- 

 sist in size, particularly of the tarsus, and in the length of the dorsal 

 plumes or train. The colors of the bill, tarsus, and the bare por- 

 tion of the tibia, which have been sometimes used as specific dis- 

 tinctions, are more or less unsatisfactory for this purpose, because 



' The Auk, XV, No. 1, January. 1S9S, p. 39. 



2 Pha'cthon rubricaudus rothschildi Mathews, Birds of Australia, IV, pt. 3, June 23, 1915, 

 p. 303 (Laysan Island). 



3 Attention has already been called by other writers to the fact that the generic name 

 Herodias Boie is a synonym of Egretta Forster, since its type is really Ardea garzetta Linnaeus, 

 as designated by Gray (List Genera Birds, 1841, p. 86). The next available name is 

 Casmerodius Gloger, as above given. 



4 Birds of Australia, III, pt. 5, March 26, 1914, pp. 431-435. 

 6 Cat, Birds Brit. Mus., XXVI, 1S9S, pp. 88-100. 



