FAMILY LARIDAE 459 



mon on both coasts, with individuals present throughout the year; 

 found regularly over Gatun Lake. 



The royal tern is known to breed on the Pacific coast from San 

 Diego Bay and Baja California to Sonora and the Islas Tres Marias ; 

 in Atlantic waters along the shores of Texas and Louisiana, on Cayos 

 Areas in the Bahia de Campeche, and from Maryland to Georgia, the 

 Bahamas, on scattered West Indian islands south to the Grenadines, 

 on Curagao and Bonaire, and at Islas Los Roques and Las Aves, 

 Venezuela. Many range to Panamanian waters in the resting period 

 of their life cycle, the majority found there having the light colored 

 crown that indicates nonbreeding dress. While they seem most abun- 

 dant in the period of Northern Hemisphere winter, the information 

 available does not indicate a clearcut schedule of migratory move- 

 ments, as they are fairly common at all seasons. It is possible that this 

 is due to their arrival and departure in Panama from both northern 

 and tropical centers, where breeding comes at different periods of the 

 year. They are found in greatest number along the Pacific coast and 

 in the Chiriqui Lagoon. 



Frequently royal terns are seen fishing over the open sea in small 

 groups of 3 to 6 or so, and at other times they are found in flocks 

 that rest on sand beaches. I have seen 20 together at La Honda 

 on the coast of Los Santos in late March, 30 to 40 at Venado Beach, 

 and 25 to 30 at the Rio Chico in February. Many come to Isla Coiba 

 where as many as 50 may congregate in Bahia Damas. Here frigate- 

 birds sometimes pursued them, but the terns seemed to have little 

 difficulty in avoiding these attacks. There are usually a number about 

 the Pacific entrance of the Canal, and a few come regularly to Gatun 

 Lake. At sea they often rest on floating logs or boards, and in the 

 Chiriqui Lagoon it is common to see them perched on poles standing 

 in shallow water. 



There is much variation in size among them, some of the females 

 being quite small. 



THALASSEUS SANDVICENSIS ACUFLAVIDUS (Cabot) : 

 Sandwich Tern; Gaviotin Patinegro 



Figure 71 



Sterna acuflavida Cabot, Proc. Boston Soc. Nat. Hist., vol. 2, 1847 (1848), 

 p. 257. (Tancah, Quintana Roo, Mexico.) 



A crested tern of medium size, with slender black bill tipped with 

 yellow. 



Description. — Length, 320 to 355 mm. Adult, in nesting season with 

 crown and crest black ; at other times crest, nape, and narrow space 



