NO. 22 BIRDS FROM CLIPPERTON ISLAND WETMORE 3 



Sula leucogaster nesiotes Heller and Snodgrass : 



Sula nesiotes Heller and Snodgrass, Condor, vol. 3, May 1901, p. 75 (Clip- 

 perton Island). 



Male with the head and neck much lighter than brewsteri or etesiaca, 

 the head in fully adult birds being almost white ; back and breast 

 more grayish, less brownish. Female with upper surface, foreneck, 

 and breast darker, more sooty gray, less brownish than breivsteri or 

 etesiaca. 



Range. — Clipperton Island, considered to range also to the Tres 

 Marias and Isabel Island, western Mexico ; a specimen assigned here 

 seen also from Manzanillo, Colima. 



Measurements (in millimeters). — (All specimens from Clipperton 

 Island, the type locality) : Males ( 1 1 specimens) , wing 360-385 (376) , 

 tail 166-205 (188), culmen from base 90.2-97.3 (93.5), depth of bill 

 at gonydeal angle 11. 7-14. 1 (12.9), tarsus 44.3-49.2 (46.7), middle 

 toe and claw 72.0-77.9 (76.3). 



Females (7 specimens), wing 385-410 (400), tail 163-200 (178), 

 culmen from base 97.6-100.8 (99.2), depth of bill at gonydeal angle 

 r 3-7 _I 5-7 ( : 4-6)> tarsus 47.1-51 (49.2), middle toe and claw 79.0- 

 86.8 (82.6). 



The extent of the light color on the head and neck of the male in 

 this race, and the darker, less brownish cast of the female, set this 

 group of birds off strikingly from brewsteri to the north and etesiaca 

 to the south, and the light color of the head that appears in males of 

 these boobies on the Pacific coast of the New World and nowhere 

 else finds in nesiotes its maximum expression. If nesiotes stood alone, 

 it is so distinct from Sula leucogaster platus, the widespread race of 

 the Pacific Ocean marked by very dark coloration, and from Sula 

 leucogaster leucogaster of Atlantic areas, in which the head and neck 

 are darker than the back and wings, that it would appear as a distinct 

 species. The connecting links are found in brczvsteri and etesiaca. 



Recently van Rossem has described another form 2 from Isabel 

 Island near the Tres Marias group as similar to breiusteri but with 

 smaller and more slender bill, paler upper parts and chest, and the 

 male with the head white. His conclusion is based in part on speci- 

 mens in the National Museum. While I have not seen van Rossem's 

 type, I have had available 9 males and 8 females from Isabel and the 

 adjacent Tres Marias Islands. These birds are identical in coloration 

 with skins from Clipperton, the type locality of nesiotes, so far as I 



2 Sula leucogastra albiccps van Rossem, Trans. San Diego Soc. Nat. Hist., 

 vol. 9, No. 4, November 21, 1938, p. 9 (Isabel Island, western Mexico). 



