FAMILY HYDROBATIDAE 43 



It is certain that other kinds will be recorded when more is 

 known of the bird life of the offshore waters. There is now a 

 sight record for a fourth, Oceanites gracilis^ and probability of 

 several others in Pacific waters. Others may come casually along the 

 Caribbean. (One present sight record in the Gulf of Panama for 

 Oceanodroma castro by C. A. Fleming (Emu, 1950, p. 177) from 

 a steamer July 20, 1948, "approaching the islands in the Bay" appears 

 uncertain.) 



KEY TO SPECIES OF HYDROBATIDAE 



1. Upper tail coverts white. 



Abdomen black Galapagos petrel, Oceanodroma tethys, p. 43 



Abdomen white Graceful storm petrel, Oceanites gracilis, p. 45 



2. Upper tail coverts dark, like the rest of the plumage. 



Smaller, not more than 150 mm. long. 



Least petrel, Halocyptena microsoma, p. 45 

 Larger, 200 mm. long, or more Black petrel, Loomelania melania, p. 47 



OCEANODROMA TETHYS (Bonaparte): Galapagos Petrel; Danzarina 



A small petrel, with upper tail coverts and lower rump white; 

 elsewhere dark colored ; tail slightly forked. 



Description. — Length 140 to 160 mm. Sooty black above ; browner 

 on the lower surface and on the wing coverts ; lower rump and upper 

 tail coverts white, with dark shafts ; some white on the outermost 

 under tail coverts. 



Iris brown ; bill, tarsus, and toes black. 



This is a bird of the Galapagos Islands and the northwest coast 

 of South America that after its breeding season ranges north in 

 the eastern Pacific to waters off northwestern Mexico. As it has been 

 found off Panama a number of times it appears that it passes regu- 

 larly through this area though probably, in the main, well at sea. 



Two subspecies separated by differences in size currently are 

 recognized with specimens of both recorded within the limits of the 

 present work. 



Robins (Condor, 1958, pp. 300-301) saw petrels of this type 

 following the fishing boat on which he traveled July 15 to 26, 1957, 

 from near Taboga to beyond Bahia Pinas, Darien. Dr. Oscar Owre 

 informs me that the specimen recorded by Robins as taken at Bahia 

 Santelmo, Isla del Rey, on July 24, was prepared as a flat skin that 

 could not be preserved permanently so that the race concerned in 

 these records is not known. 



Dennis R. Paulson, when a student at the Institute of Marine 



