BIRDS OF NORTH AND MIDDLE AMERICA. 673 



Family STERCORARIID^. 



THE SKUAS AND JAEGERS. 



=Leslrinx Bontaparte, Saggio dist. Anim. Vertebr., 1831, 60. 



=Lestridx Kaup, Jardine's Contr. Orn., 1849, 119. 



= Lestndinx Bonaparte, Consp. Gen. Av., ii, 1857, 20G. — Lawrence, in Baird, 

 Rep. Pacific R. R. Surv., ix, 1858, 837.— Carus, Handb. Zool., 1868, 

 361.— CouES. Proc. Ac. x\at. Sci. Phila., 1869, 213; Key N. Am. Birds, 1872, 

 308; 2d ed., 1884, 734; Birds Northwest, 1874, 602.— Sclater and Salvin, 

 Nom. Av. Neotr., 1873, 148. 



=5'<ercommna? Gray, Hand-list, iii, 1871, 110. — Beddard, Struct, and Classif. 

 Birds, 1898, 356.— Knowlton, Birds of the World, 1909, 394. 



=Stercorariid3e Ridgway, Proc. U. S. Nat. Mus., iii, Sept. 4, 1880, 240; Man. 

 N. Am. Birds, 1887, 20. — Bairl», Brewer, and Ridgway, Water Birds N. 

 Am., ii, 1884, 191, 323.— Stejneger, Standard Nat. Hist., iv, 1885, 75, 

 in text. — American Ornithologists' Union, Check List, 1886, 84; 3rd ed., 

 1910, .33.— Sharpe, Review Rec. Att. Classif. Birds, 1891, 72; Hand-Ust, 

 i, 1899, XV, 143. — Saunders, Bull. Brit. Orn. Club, no. xxxiii, 1896, p. 

 xxii; Oat. Birds Brit. Mus., xxv, 1896, xiv, 3, 314. — Oberholser, OutL 

 Classif. N. Am. Birds, 1905, 3. 



Medium sized to large Lari witli rhampliotlieca complex (bill 

 with a cere); caeca well developed, long; coracoids separated; meta- 

 sternum 2-notclied, and claws large, strongly hooked, and sharp. 



Bill gull-like in general form, but basa] half or more of the culmen 

 covered with a saddle-like "cere," membraneous or horny, ac- 

 cording to the season," the lower edge of which reaches half way or 

 more to the tomium and is nearly parallel to it, its upper outline 

 straight; culmen strongly decurved from anterior end of the "cere," 

 the tip of the maxilla forming a distinct unguis, overhanging the 

 tip of the mandible; gonys short (decidedly less than half as long 

 as mandibular rami), ascending terminally, its posterior angle more 

 or less prominent; nostril slightly anterior to middle of maxilla, 

 longitudinal, rounded antei'iorly, partly overhung (except at anterior 

 extremity) by edge of the "cere;" frontal feathering advancing 

 farther on side of maxilla than at base of culmen, the antia either 

 acute, rounded, or nearly truncate; malar antia more or less pos- 

 terior to latero-frontal antia, but sometimes nearly on same vertical 

 line, more or less cuneate; mental antia about on same vertical 

 line as posterior end of nostrils or posterior to same. Wing long 

 and pointed, the longest primary (outermost) exceeding distal 

 secondaries by about two-thirds (Stercoranus) to half {Megalestrls) 

 the length of the wing. Tail much shorter than wing (ex- 

 cept for the elongated middle rectrices in some species), slightly 

 rounded to slightly graduated, the middle pair of rectrices longest, 

 sometimes greatly elongated. Feet stiong, the tarsus decidedly 

 longer than middle toe without claw, the acrotarsium regularly 

 transversely scutellate, elsewhere covered w^ith reticulation^. 

 '^ See Stejneger, Standard Nat. Hist., iv, 1885, 75. 

 40017— 19— Bull. 50, pt 8 44 



