BIRDS OF NORTH AND MIDDLE AMERICA. 673 
Family STERCORARIIDA. 
THE SKUAS AND JAEGERS. 
=Lestrine Bonaparte, Saggio dist. Anim. Vertebr., 1831, 60. 
=Lestride Kaup, Jardine’s Contr. Orn., 1849, 119. 
= Lestridine BoNAPARTE, Consp. Gen. AV., ii, 1857, 206.—LAWRENCE, in Baird, 
Rep. Pacific R. R. Surv., ix, 1858, 837.—Carus, Handb. Zool., 1868, 
361.—Cougs. Proc. Ac. Nat. Sci. Phila., 1869, 218; Key N. Am. Birds, 1872, 
308; 2d ed., 1884, 734; Birds Northwest, 1874, 602.—ScLater and Savin, 
Nom. Av. Neotr., 1873, 148. 
=Stercorartine Gray, Hand-list, iii, 1871, 110.—Brpparp, Struct. and Classif. 
Birds, 1898, 356.—Know ton, Birds of the World, 1909, 394. 
=Stercorartide Ripeway, Proc. U. 8. Nat. Mus., iii, Sept. 4, 1880, 240; Man. 
N. Am. Birds, 1887, 20.—Barrp, Brewer, and Ripaway, Water Birds N. 
Am., ii, 1884, 191, 328.—Srzsnecer, Standard Nat. Hist., iv, 1885, 75, 
in text.—AmeErRicaN OrnitHoLoaists’ Union, Check List, 1886, 84; 3rd ed., 
1910, 33.—Suarprg, Review Rec. Att. Classif. Birds, 1891, 72; Hand-list, 
i, 1899, xv, 143—Saunpers, Bull. Brit. Orn. Club, no. xxxiii, 1896, p. 
xxii; Cat. Birds Brit. Mus., xxv, 1896, xiv, 3, 314.—OsBEruHo.seER, Outl. 
Classif. N. Am. Birds, 1905, 3. 
Medium sized to large Lari with rhamphotheca complex (bill 
with a cere); caeca well developed, long; coracoids separated; meta- 
sternum 2-notched, and claws large, strongly hooked, and sharp. 
Bill gull-like in general form, but basal 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 anteriorly, 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 (Stercorarius) to half (Megalestris) 
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 strong, the tarsus decidedly 
longer than middle toe without claw, the acrotarsium regularly 
transversely scutellate, elsewhere covered with reticulations. 
2 See Stejneger, Standard Nat. Hist., iv, 1885, 75. 
40017—19—Bull. 50, pt 844 
