A SYNOPSIS OF THE KACES OF THE CRESTED TERN, 

 THALASSEUS BERGII (LICHTENSTEIN). 



By Harey C. Oberholsee, 



Of the Biological Survey, United States Department of Agriculture. 



The identification of United States National Museum material 

 collected in the East India Islands by Dr. W. L. Abbott has involved 

 a canvass of all the races of Thalasseus hergii. Some of these have a 

 more or less uncertain status, owing to the divergent views of recent 

 authors;^ and the following conclusions, based upon a careful study 

 of the questions involved, throws, I hope, a little further light on the 

 relationships and geographical distribution of the various subspecies. 

 Although the specimens examined have not been numerous, only 

 about 45, they are of importance since none of them was available 

 to either Mr. Mathews or Mr. Stresemann, the two authors who have 

 most recently monographed the species. These specimens comprise 

 the collections of the United States National Museuxn and the 

 Museum of Comparative Zoology at Cambridge, Massachusetts, and 

 include birds from most ports of the range of the species, together 

 with the types of Sterna rectirostris Peale and Sterna hergii horeotis 

 Bangs. While I have been unable to see examples of Thalasseus 

 hergii thalassinus, Thalasseus hergii velox, Thalasseus hergii hakeri 

 or Thalasseus hergii gwendolenae, the measurements of these races 

 given by Mr. Stresemann, ^ together with notes which Mr. Mathews, 

 who has had access to Mr. Stresemann's material, has very kindly 

 furnished, have very well supplied the deficiency. 



Measurements in this paper are aU in millimeters, and those in the 

 tables have been taken as in the author's recent paper on Butorides 

 virescens.^ For the sake of comparison I have added the wing 

 measurements of each race as given by Mr. Stresemann;^ since, owing 

 to the fact that these are invariably greater than my own, there 

 seems to be indication of a difference in our methods of measuring. 



• Bangs, Bull. Mus. Comp. Zoo!., vol. 36, 1901, p. 257; Mathews, Birds of Australia, vol. 2, pt. 3, Sept. 

 20, 1912, pp. 346-347: Stresemann, Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. 

 » Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. 

 » Oberholser, Proc. U. S. Nat. Mus., vol. 42, Aug. 29, 1912, p. 533. 

 « Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. 



Proceedings U. S. National Museum, Vol. 49— No. 2121. 



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