BIRDS OF NORTH AND MIDDLE AMERICA. 527 
KEY TO THE SPECIES AND SUBSPECIES OF HYDROCHELIDON. 
a, Under parts not white; pileum uniform black. (Summer adults.) 
b. Upper tail-coverts and lower rump gray, concolor with back, etc.; smaller 
wing-coverts not conspicuously paler than back. 
ce. Sides of head white; under parts pale gray anteriorly, becoming much darker 
gray on flanks and abdomen; larger (wing 213.5-249, tarsus 19-22). (Southern 
and central Europe to China, Philippines, Australia, Africa, etc.; accidental 
in Barbados,).............c2eeeeeee ees Hydrochelidon leucopareia (p. 528). 
ce. Whole head, neck, and under parts (except anal region and under tail- 
coverts) uniform black or deep gray; smaller (wing 191-215, tarsus 14-18). 
(Hydrochelidon nigra.) 
d, Under parts gray (light purplish gray to blackish purple-gray). (Europe 
and western Asia; Africa in winter.) 
Hydrochelidon nigra nigra (extralimital).2 
dd. Under parts black. (North America, south in winter as far as Chile.) 
Hydrochelidon nigra surinamensis (p. 532). 
bb. Rump white, in contrast with dark gray or grayish black of back; smaller 
wing-coverts conspicuously paler than back, passing into white anteriorly. 
(Warmer parts of Eastern Hemisphere; accidental in Wisconsin and Barbados.) 
Hydrochelidon leucoptera (p. 536). 
aa. Under parts white; pileum not uniform black. 
b. Back, scapulars, etc., uniform gray. (Winter adults.) 
c. Rump gray, concolor with back, etc. 
d. Larger (wing 213.5-249, tarsus 19-22); upper parts much paler gray; bill 
Dro wish joseieivan0 seems Hydrochelidon leucopareia, winter adults (p. 528). 
dd. Smaller (wing 191-215, tarsus 14-18); upper parts much darker gray; bill 
blackvecsssccexs Hydrochelidon nigra nigra, winter adults (extralimital). 
Hydrochelidon nigra surinamensis, winter adults (p. 533). 
ec. Rump white. ............- Hydrochelidon leucoptera, winter adults (p. 537). 
@ [Sterna] nigra Linneeus, Syst. Nat., ed. 10, i, 1758, 137 (Sweden).—Sterna nigra 
Selby, Brit. Birds, ii, 1833, 477, pl. 91;Gould, Birds Europe, v, 1837, pl. 422; Nau- 
mann, Vig. Deutschl., x, 1840, 189, pl. 256.— Hydrochelidon nigra Boie, Isis, 1822, 563; 
Macgillivray, Brit. Birds, v, 1852, 658; Gould, Birds Great Brit., v, 1873, pl. 75 and 
text; Dresser, Birds Europe, viii, 1876, 327, pl. 592; Saunders, Proc. Zool. Soc. Lond., 
1876, 642 (monogr.); Cat. Birds Brit. Mus., xxv, 1896, 17;-ed. Yarrell’s Hist. Brit. 
Birds, iii, 1884, 516; Man. Brit. Birds, 1889, 617.—Hydrochelidon nigra nigra American 
Ornithologists’ Union, Check List, 3d ed., 1910, 47.— Viralva nigra Stephens, Shaw’s 
Gen. Zool., xiii, pt. i, 1826, 167.—Hydrochelidon nigrum Bonaparte, Geog. and Comp. 
List, 1838, 61.—[Rallus] lariformis Linneeus, Syst. Nat., ed. 10, i, 1758, 153 (Europe).— 
[Hydrochelidon lariformis.] a. (European references) Couzs, Birds Northwest, 1874, 
704.—[Sterna] nxvia Linneeus, Syst. Nat., ed. 12, i, 1766, 228 (south Europe=young).— 
Larus merulinus Scopoli, Ann. I. Hist. Nat., 1769, 81.—(?)Larus columbinus Scopoli, 
Ann. I. Hist. Nat., 1769, 83.—Sterna nubilosa Sparrman, Mus. Carls., fasc. iii, 1788, 
no. 63 (Finland;=young).—Sterna fissipes (not of Linnzus) Latham, Index Orn., ii, 
1790, 810; Bechstein, Naturg. Deutschl., ii, 1791, 833; Yarrell, Brit. Birds, iii, 1843. 
413; ed. 2, iii, 1845, 523; Schlegel, Mus. Pays-Bas, vi, Sternae, 1863, 29; Harting, Handb, 
Brit. Birds, 1872, 76.—Hydrochelidon fissipes Bonaparte, Cat. Ucc. Eur., 1842, 77; 
Degland and Gerbe, Orn. Eur., ii, 1867, 465; Fritsch, Vég. Eur., 1870, 462, pl. 54, 
fig. 6; Salvadori, Fauna Ital., Ucc., 1871, 284.—Hydrochelidon obscura Brehm, Vég. 
Deutschl., 1831, 795.—Hydrochelidon nigricans Brehm, Vég. Deutschl., 1831, 795.— 
Hydrochelidon pallida Brehm, Naumannia, 1855, 295; Vogelf., 1855, 350.—Hydro- 
chelidon obscura Brehm, Naumannia, 1855, 295; Vogelf., 1855, 350. 
