458 BULLETIX 50, UNITED STATES :N'ATI0NAL MUSEUM. 



Family STERNID.E. 



THE TERNS. 



=Sterninx Bonaparte, Geog. and Comp. List Birds Europe and N. Am. 1838, 61; 

 — Lawrence, in Baird, Rep. Pacific R. R. Surv., ix, 1858, 837, 858. — Carus. 

 Handb. Zool., i, 1868, 362.— Coues, Proc. Ac. Nat. Sci. Phila., 1869, 214, 

 Key, 1872, 317; 2d ed., 1884, 734, 754.— Sclater and Salvin, Norn. Av. 

 Neotr., 1873, 147. — Baird, Brewer, and Ridgway, Water Birds N. Am., 

 ii, 1884, 196, 197.— Saunders, Cat. Birds Brit. Mu8., xxv, 1896, xiii, 3, 4.— 

 American Ornithologists' Union, Check List, iS86, 92. — Gadow, in 

 Bronn's TIiier-Reich, Yog., ii, 1891, 205. — Beddard, Struct, and Classif. 

 Birds, 1898, 356.— Sharps, Hand-list, i, 1899, xiv, 133.— Salvin and Godman, 

 Biol. Centr.-Am., Aves, iii, 1903, 397. — Knowlton, Birds of the World, 

 J 909, 390. 



=Sternidae Reichenow, Yog. Zool. Gart., i, 1882, 27. 



Medium-sized to very small Lari with the bill nearly straight, 

 relatively narrow (vertically), with terminal portion of culmen not 

 strongly if at all decurved, its depth at gonydeal angle usually less 

 (never more) than at middle of nostril, the exposed culmen at least 

 one and one-fourth times (sometimes nearly three times) as long as 

 tarsus; feet relatively small, the tarsus little if any more than one- 

 ninth (usually less than one-tenth, sometimes only one-nineteenth) 

 as long as wing; tail usually (often deeply, sometimes excessively) 

 forked, rarely graduated; thigh-muscle formula with B (except in 

 Gygis); expansor secundariorum muscle absent (except in Anous); 

 pterylosis typically charadriine. 



The Sterniidoe are closely related to the Larid», but seem to be 

 sufficiently distinct to merit family rank. Although single characters 

 often occur in both groups, every species is, nevertheless, distinctly 

 and unmistakably either a Tern or a GuU. 



The Sternidse are as a rule birds of smaller size, lighter build, and 

 more graceful form and actions than the Laridae, and obtain their 

 food in a different manner, pouncing suddenly on it from the air and 

 striking it with their sharp bills. From this habit the vernacular 

 name ''Striker" is applied to them on the coast of Virginia and 

 elsewhere. Their nidification is closely similar to that of the Laridse. 



KEY TO THE GENER.\ OF STERNID^E. 



a. Tarsus longer than first two phalanges of middle toe, more than one-fifteenth as 

 long as wing, more than one-third (usually one-half or more) as long as exposed 

 ^culmen, the latter more or less decurved terminally; webs between anterior 

 toes not deeply incised; coloration not wholly white. 

 b. Tail simply forked (more or less deeply), the lateral pair of rectrices longest or 

 equal to the long(>st. 

 c. Frontal feathering advancing farthest anteriorly on sides of maxilla, where 

 forming a distinct (though sometimes obtuse) angle immediately behind 

 nost ril . 



