2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



California, is distinct and to be recognized as a separate geographic 

 race under the name ncsiotes given it years ago by Heller and 

 Snodgrass. 



The identification of these birds from Clipperton Island has led to 

 examination of all the boobies of this group from the west coast of 

 the New World from Baja California to Gorgona Island, Colombia, 

 with results that are of interest. While apparently uniform over large 

 areas of the tropical oceans of other parts of the world there are three 

 (barely possibly four) races of Sula leucogaster to be recognized in 

 the limited area on the Pacific coast of the Americas under considera- 

 tion. These differ from all other subspecies of the species in question 

 in having the head in the male in part, or entirely, distinctly lighter 

 than the neck and upper parts. Following are notes on these races : 



Sula leucogaster brezusteri Goss: 



Sula breivsteri Goss, Auk, 1888, p. 242 (San Pedro Martir Island, Gulf of 

 California). 



Male with the head partly light in color, the paler area confined 

 mainly to the face ; female with upper surface, head, and neck brownish 

 (uniform in shade like S. I. plot us of widespread distribution farther 

 west in the Pacific but lighter colored). 



Range. — Baja California, including the Gulf of California, to the 

 Revillagigedo Islands. 



Measurements (in millimeters). — Males (6 specimens), wing 375- 

 397 (384), tail 178-196 (187), culmen from base 90-95.3 (93.2), 

 depth of bill at gonydeal angle 11.0-13.6 (12.4), tarsus 46.5-52.1 

 (48.5), middle toe with claw 76.9-78.8 (78.0). 



Females (7 specimens), wing 389-414 (403), tail 176-198 (189), 

 culmen from base 93.7-104 (98.4), depth of bill at gonydeal angle 

 12. 5-14. 7 ( 13.2), tarsus 48.5-54 (51.5), middle toe with claw 76.9-78.8 



(/8). 



In these measurements there are included data from three specimens 

 in the Carnegie Museum from San Benedicto, Revillagigedo Islands, 

 made available to me by A. J. van Rossem. In comparing the meas- 

 urements of breivsteri and the other races here discussed the length 

 of the tail is included but has not been considered in comparative 

 studies of size as the rectrices in these boobies are often subject to 

 much abrasion, depending probably upon the conditions under which 

 the bird habitually perches, whether on sand or rock. 



