464 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



RYNCHOPS NIGRA Linnaeus: Black Skimmer; Rayador 

 Figure IZ 



Like a large tern in form, with a laterally compressed, knifelike 

 bill, in which the lower mandible is much longer than the upper. 



Description. — Length, 410 to 460 mm. Adult, in breeding plumage, 

 sooty black above; wing coverts somewhat browner; secondaries 

 tipped narrowly with white; tail dark gray edged with white; fore- 

 head and lower surface white ; under wing coverts pale gray. 



Postbreeding adults and immature, browner above, with a white, 

 or grayish white band on the hindneck. 



Fig. Ti. — Head of black skimmer, rayador, Rynchops nigra. 



The black skimmer in the north is mainly a bird of ocean beaches 

 and salt-water inlets, but in South America it also ranges widely along 

 the larger rivers. As the few reports for Panama come from both 

 coasts, two geographic races probably are represented, though only 

 one from the Caribbean side to date has been verified by a specimen. 



RYNCHOPS NIGRA NIGRA Linnaeus 



Rynchops nigra Linnaeus, Syst. Nat., ed. 10, vol. 1, 1758, p. 138. (Coast of 



South Carolina.) 

 Rynchops nigra oblita Griscom, Ibis, ser. 13, vol. 5, no. 3, July 1, 1935, p. 545. 



(Laguna Acapam, Pacific coast of Guatemala.) 



Characters. — White edgings on secondaries broader; tail more ex- 

 tensively white; underwing coverts usually white, though in some 

 tinged with gray ; somewhat smaller. 



Measurements.— Males, wing 364-401 (380), tail 112.0-128.1 

 (120.4), culmen 63.7-73.8 (69.5), tarsus 30.8-37.8 (34.8) mm. 



