145 



TERNS (LARIDAE, subfamily STERNINAE) 



Although in the gull family, terns really bear little resemblance to gulls 

 except that some have a'color pattern, i.e., "gull gray" above and white 

 below, similar to some of the larger gulls. The combination of a slender, 

 sharply pointed bill (no hook; Plates 29-30), short legs, a long tail that 

 is usually forked, and, especially, long, narrow and pointed wings is 

 characteristic of species in this group. The petrels also have long, 

 narrow wings. Whereas the latter achieve greater wing length by a 

 relative extension of proportions from shoulder to wrist, terns do so by 

 having very long primary feathers. Thus, the wrist outward is the major 

 portion of a tern's wing. We can really not add much more to what has 

 been presented in the keys in the way of additional identification charact- 

 eristics. One should be aware, however, that it is perhaps more likely to 

 find a dead pigeon (ROCK DOVE) on the beach than it is to find a tern in 

 many areas along the Pacific coast, and should only the wings of a pigeon 

 be found, it will probably "key" to terns in the Key to Keys. A pigeon's 

 wings are much broader than a tern's. 



Most terns are tropical or subtropical in distribution. In general, 

 they occur either in estuarine or very protected waters, or they occur 

 far at sea. As a result, they are infrequently encountered as beached 

 specimens . 



GULL-BILLED TERN (Gelochelidon nilotioa; choices 13 and 13', pg. 63) 

 If a specimen still has its head and one has decided it is a tern, then 

 the heavily proportioned bill (Plate 30) (somewhat like that of a 

 Bonaparte's Gull) should confirm its identity. It is very unlikely that 

 this species will be encountered in the area covered by this manual. 

 Gull -billed Terns occur inland in southern California (Sal ton Sea) and 

 from there south along the Sonora, Mexico coast (to Ecuador). Thus, if 

 they are to be found anywhere along the Pacific coast, it would be most 

 possible in the Baja California segment. Any specimen found should be 

 saved for verification. 



FORSTER'S TERN (Sterna forsterij choices 18 and 18', pg. 64), COMMON 

 TERN (S. hirundo; choices 22 and 22', pg. 64) and ARCTIC TERN (S. paradisaea; 

 choices 23 and 23', pg.65 ) These species are quite similar in size and 

 in other characteristics. Characters mentioned in the key should usually 

 suffice in distinguishing them but some others may at times help. 

 Although outer tail feathers are subject to a great deal of wear, in the 

 outer tail feathers of the Forster's Tern the inner and outer vanes 

 should be gray and white, respectively. In the other two species the 

 outer web should be gray. The bill of an Arctic Tern is usually entirely 

 a deep, blood red (sometimes dark at tip); in the other two it has a good 

 deal of black at the tip and the red, if present (in summer quite 

 extensively so), is more orange. 



