10 ARKIV FÖR ZOOLOGI. BAND 13. NIO 4. 



elements from the main or the smaller birds are completely 

 isolated from their sister birds on the mainland, judging by 

 the endemic forms, we, however, must define this fauna 

 only as a part of the Panaman one, the composition of which 

 agrees with the small life area presented by the Islands and the 

 existing biological conditions. 



In the following list North American birds occurring only 

 as winter visitors or during migration are marked with an 

 asterisk, measurements are in millimetres, and the colours 

 are according to Ridgway: Color Standards and Color Nomen- 

 dature, Washington 1912. 



IV. List of Species. 



Fam. Sulidae. 



1. Sula etesiaca (Thayer and Bångs). 



Sula sp. Salvador:, Boll. IMus. Torino, XIV, 1899, no. 339, 13 (Pearl Is- 

 lands). 



Sula leucogastra Salvin and Godman, Biol. Centr.- Am. Aves, III, 1901, 149 

 (Pearl Islands, in ref. to Salvadori's record). 



Sula etesiaca Thayer and Bångs, BuU. Mus. Comp. ZoöL, XLVI, 1905, 141 

 (San Miguel, Saboga). 



Thayer and Bångs described (Bull. Mus. Comp. ZoöL, 

 XLVI, 1905, 92) this species based upon specimens from 

 Gorgona I. off the coast of Colombia, 8an Miguel I., and 

 Saboga I. (type sp. from Gorgona I.) and stated it also as 

 being the Booby occurring in the Cocos Island. We don't 

 know the northern limit for the distribution of this species, 

 Carriker, however, states it (Ann. Carn. Mus. VI, 1910, 439) 

 breading in Costa Rica on the rocky islets off the coast a little 

 north of the delta of the Rio Grande de Térraba and it would 

 seem, that the Boobies met with at the Pacific side of Costa 

 Rica are to be referred to this species, while S. leucogastra is 

 found along the Caribbean coast. 



Dr. BovALLius found the Booby abundant in P a c h e c a, 

 inhabiting the northern part of that island. 



He also met with great flocks of Boobies at C h e p i 1 1 o 

 Island. 



