FAMILY SULIDAE 63 



nesting sites on small ledges on the higher cliffs. Some of these held 

 nearly grown young. The largest colony that I have seen is on Isla 

 Bona, where I observed them in numbers flying off the steep rocky 

 slopes on March 31, 1962. Robins (Condor, 1958, pp. 301-302) in 

 July 1957 found this the most common booby around Isla Camote 

 and Isla Galera and off the coast between Punta Garachine and 

 Bahia Piiias, Darien. This seems to imply either more extensive 

 breeding colonies than have been reported or that birds that nest 

 elsewhere come to the Gulf of Panama when food is abundant. I 

 saw one near Isla Pelado, off the mouth of the Rio Chiman, on 

 February 15, 1950, but noted no indication of nesting. A specimen in 

 the American Museum of Natural History was taken by Dr. Murphy 

 on the Askoy Expedition, at Ensenada Guayabo, southern Darien, on 

 March 2, 1941. 



As these boobies circle and swing about they appear very large 

 against the sky. When seen from the side the gray-brown head 

 and neck are outlined clearly from the white breast. 



The population found at the Galapagos Islands has been separated 

 by Todd (Proc. Biol. Soc. Washington, 1948, p. 99) as Sula 

 nehouxii excisa on the basis of average larger size. Murphy (Oceanic 

 Birds S. Amer., 1936, p. 830), the first to point to this distinction, 

 listed wing measurements as follows : 



Pacific coast, 7 males, 387-413 ; 7 females, 403-426 mm. 



Galapagos Islands, 3 males, 406-433 ; 3 females, 444-448 mm. 



The difference is slight but appears valid in the specimens that I 

 have examined. 



SULA SULA SULA (Linnaeus): Red-footed Booby; Boba Blanca 



Pelecamis Sula Linnaeus, Syst. Nat., ed. 12, vol. 1, 1766, p. 218. (Barbados.) 



Adult, white or grayish brown ; tail white in both phases. 



Description. — Length 660 to 700 mm. Adult, white, with primaries 

 black, washed with gray on the outer webs ; or in the darker color 

 phase, grayish brown, with rump and tail white. 



Immature, plain grayish brown. 



Gular sac black in males, bluish black in females ; feet red. 



Measurements (from Murphy, Oceanic Birds S. Amer., vol. 1, 

 1936, p. 862).— Males (9 specimens), wing 362-385 (372.1), tail 

 206-231 (217), exposed culmen 76.3-85 (81.2), tarsus Z2.7-Z6.9 

 (33.7) , middle toe and claw 66.2-74.5 (69) mm. 



Females (7 specimens), wing 378-405 (389), tail 198-215 (207.4), 



