448 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



The only reports are those of Robert Cushman Murphy (Vert. 

 SCOPE, Nov. 7-Dec. 16, 1956, p. 137, mimeograph, and in litt.) 

 who says that this species was seen occasionally southward to the 

 latitudes of Panama but far at sea between long. 88° and 100° W. 



In 1941, during the cruise of Askoy, however, he saw 8 Sabine's 

 gulls close along the coast of southern Darien, and later, on May 11, 

 1941, he collected two to the southward in Bahia Cuevita, below 

 Cabo Corrientes, on the northwestern coast of Colombia. 



The species nests in the far north, and in migration moves south 

 off the Pacific coast of America as far as Peru. 



CHLIDONIAS NIGER SURINAMENSIS (Gmelin) : Black Tern; 

 Gaviotfn Negro 



Sterna surinamensis Gmelin, Syst. Nat., vol. 1, pt. 2, 1789, p. 604. (Surinam.) 



A small tern ; adult in breeding dress, black on head and lower sur- 

 face; immature and winter adult, tail dark gray (white, or mainly 

 white, in other terns) ; bill, tarsi, and feet black. 



Description. — Length, 230 to 250 mm. Adult, breeding dress, en- 

 tire head and under surface back across abdomen sooty black ; anal 

 region and under tail coverts white ; back, rump, wings, and tail dark 

 gray. 



Winter dress and immature birds, anterior half of crown, fore 

 neck, and under surface white ; spot on either side of breast dusky ; 

 rest of upper surface as in summer. 



Measurements (from Ridgway, I.e., p. 533). — Males, wing 192-213 

 (203.2), tail 73-87.5 (79.8), culmen 26-29.5 (27), tarsus 14.5-16 

 (15.4) mm. 



Females, wing 191-215 (199.6), tail 73.5-82 (77.8), culmen 25.5- 

 27 (26.2), tarsus 14-16.5 (15.6) mm. 



Migrant from the north. Common along the coast, and in the 

 Gulf of Panama ; ranges regularly over Gatun Lake, and other larger 

 inland bodies of open water. 



The flight from the north comes in September and continues 

 through October. Northward movement appears to begin in April 

 and to extend well into May, On May 13, 1953, at sunrise I found 

 many passing toward the north across the dry savannas near Rio 

 Hato in the Province of Code on a course that would carry them 

 over the low divide to the Caribbean west of the Canal Zone. Two 

 that I shot, male and female, were in worn plumage and were molting 

 the wing and tail feathers but did not show any of the black body 

 plumage of the nesting season. Considerable numbers of nonbreed- 



