FAMILY LARroAE 45I 



longer tarsus. The following measurements are taken from speci- 

 mens in the Museum of Comparative Zoology and the U. S. Na- 

 tional Museum. 



Measurejnents.—S males, wing 287-295 (291.4), tail 102.5-119.0 

 (111.6), culmen from base 41.4-46.5 (43.8), tarsus 32.0-35.2 (33.2) 

 mm. 



3 females, wing 287-298 (292), tail 98.7-115.0 (104.4), culmen 

 from base 42.9-44.5 (43.6), tarsus 32.9-33.3 (33.1) mm. 



Wing and tail measurements are difficult to ascertain, since many- 

 specimens show much wear, even breakage in the slender tips of 

 the longer feathers. Also, immature birds in their first winter do 

 not appear to develop full bill and tarsus size until they have been 

 for some time on the wing. 



The specimens now known from Panama (including the two col- 

 lected by Benson) all agree in size with the race aranea. It appears, 

 therefore, that these birds, like the laughing gull, in southward mi- 

 gration cross in part to winter on the Pacific side of Panama. 



HYDROPROGNE CASPIA (Pallas): Caspian Tern; Gaviotfn Piquirojo 

 Sterna caspia Pallas, Novi Comm. Acad. Sci. Petrop., pt. 1, 1770, p. 582, pi. 22. 

 (Caspian Sea, southern Russia.) 



Dififers from the royal tern in red bill, tail only slightly forked, 

 and elongated crest feathers rounded, with the free ends smoothly 

 blended. 



Description. — Length, 480 to 540 mm. Adult (sexes alike) in 

 breeding dress, crown including upper half of lores and side of head 

 immediately behind eye, black; rest of upperparts light gray, be- 

 coming white on upper tail coverts, and pale grayish white on tail; 

 line on lower eyelid, and under surface, including under wing 

 coverts, white ; inner webs of primaries dark gray. 



Winter plumage, crown, including forehead and side of head, 

 dusky black streaked with white. 



Immature, upperparts paler, with a few dusky spots ; crown with 

 more white. 



Iris dark brown; bill deep red, with the tip orange or yellowish 

 orange ; legs and feet black. 



Measurements. — (from Ridgway, I.e., p. 462). — Males, wing 400- 

 422 (411.1), tail 130-150 (137.9), exposed culmen 65-75 (69.4), 

 tarsus 40.5-46 (43.2) mm. 



Females, wing 404-423 (416), tail 135-148 (140.2), exposed cul- 

 men 64-70 (67.5), tarsus 40-44 (42.4) mm. 



Migrant from the north. One record at Aligandi, San Bias. 



