FAMILY LARIDAE 



443 



Immature, above, mainly grayish brown ; tail light gray at base, dull 

 black at end, tipped obscurely with white ; underneath grayish brown 

 except for the abdomen, which is paler. 



Measurements. — Males, wing 316-348 (332.7), tail 121-135 

 (127.6), culmen 40-43 (41), tarsus 47-53 (50.4), middle toe 34.5- 

 38 (36) mm. 



Fig. 70. — Right wings of two gulls to show pattern of marking. Upper : Frank- 

 lin's gull, gaviota de Franklin, Larus pipixcan. Lower : Laughing gull, gaviota 

 reidora, Larus atricilla. 



Females, wing 311-331 (322), tail 116-125.5 (120.2), culmen 38- 

 40 (39.1), tarsus 46-51.5 (48.1), middle toe 32.5-35 (33.5) mm. 



Migrant from the north. Found along both coasts, abundant in the 

 Bay and Gulf of Panama; common on Gatun Lake, and casual on 

 other larger bodies of water inland. Recorded regularly at Isla Coiba, 

 and occasionally around other offshore islands. Nonbreeding in- 

 dividuals remain through the period of northern summer. 



The main influx from the north comes in October and November, 

 and during succeeding months the birds are widely spread. Molt into 



