FAMILY LARIDAE 447 



Iris brown ; edge of eyelids and edge of gape bright red ; tip of 

 bill greenish ; base black ; tarsus and toes pink. 



Measurements (from Murphy, I.e., p. 1086). — Males, wing 405- 

 433 (414.8) ; tail 184-202 (191.1), culmen 47-55 (52), tarsus 45-55 

 (52.1) mm. 



Females, wing 393-414 (404.1), tail 181-197 (189.7) culmen 49- 

 52 (50.9), tarsus 47-54 (51) mm. 



Visitor from the south. Casual. 



The only record is that of Robins (Condor, 1958, p. 302) who 

 recorded one seen at a deep reef northwest of Bahia Pinas, July 18, 

 1957. I have found no basis for the statement by Swarth (Occas. 

 Papers California Acad. Sci., vol. 18, 1931, p. 66) that "one or two 

 stragglers have been found on the coast of Panama." 



The fork-tailed gull breeds at the Galapagos Islands, and after 

 the breeding season it is found at sea as far as the coasts of Ecuador 

 and Peru. It nests also on Isla de Malpelo, approximately 500 

 kilometers west of Buenaventura, on the coast of Colombia, and about 

 400 kilometers due south of Isla Coiba. 



XEMA SABINI (Sabine): Sabine's Gull; Gaviota de Sabine 



Larus sabini J. Sabine, Trans. Linn. Soc. London, vol. 12, pt. 2, 1819, p. 522, 

 pi. 29. (Sabine Islands, near Melville Bay, west coast of Greenland.) 



A small gull, with a deeply forked tail. 



Description. — Length, 300 to 350 mm. Adult, summer dress, head 

 slate-colored, with a narrow black ring around the neck ; back, lesser 

 wing coverts, secondaries, scapulars, and tertials dark gray; outer 

 webs of outer primaries black, tipped with white; inner primaries, 

 tips of secondaries, tail, upper tail coverts, and under parts white; 

 edge of wing black. 



Winter dress, head and neck mainly white, with occiput, nape, 

 and auricular region brownish gray. 



Immature, grayish brown above, with feathers edged with dull 

 white to grayish buffy white; tail white, with a broad subterminal 

 band of black, and a white or grayish tip. 



Measurements (from Ridgway, I.e., p. 664). — Males, wing 265- 

 286 (277.2), tail 114.5-130 (122.4), culmen 25.5-28.5 (27.4), tarsus 

 31.5-34.5 (33.1) mm. 



Females, wing 260-276 (267.5), tail 111-114.5 (112.2), culmen 

 25-27 (26.2), tarsus 30-32 (31.5) mm. 



Migrant from the north. Casual. 



