143. Circus hudsonius, (Linn.)
Probably the most common species of Hawk during the winter months, arriving in September and leaving in April. A large propor- tion are in immature plumage. — (Dresser, Ibis, 1865, 328. — 0. cyaneus hudsonius, Sennett, B. Rio G-rande, 40.)
144. Nisus fuscus, (Gruel.)
Found sparingly in winter. — (Accipiter /., Dresser, Ibis, 1865, 324.)
145. Nisus cooperi, (Bon.)
Like the last. — (Accipiter <?., Dresser, Ibis, 1865, 323.— Sennett, B. Rio Grande, 42.)
146. Antenor unicinctus var. haxrisi, (Aud.)
Resident and quite abundant. In its habits, this bird resembles the Oaracara Eagle, but is not so active. The nests are hardly distinguish- able in situation or construction, and the two eggs are also deposited at an interval of three or four days. Six eggs average 2.08 by 1.62 ; they are dull bluish or yellowish- white, faintly stained with yellowish- brown. — (Craxirex unicinctus, Dresser, Ibis, 1865, 329.— Buteo unicinc- tus harrisi, Sennett, B. Rio Grande, 42.)
147. Buteo pennsylvanicus, (Wils.)
Uncommon winter visitor. — (Dresser, Ibis, 1865, 325. — Sennett, B. Rio Grande, 43.)
148. Buteo swainsoni, Bon.
Occurs sparingly in winter. — (DRESSER, Ibis, 1865, 324.)
149. Buteo borealis, (Gmel.)
A pair seen January 10, 1877, near Fort Brown, seemed to approach var. Jcrideri in the extent and purity of white beneath, although the subterminal band of black on the tail was very distinct. The birds sailed several times quite near me, and I had a very good view of them.— (Dresser, Ibis, 1865, 324.)
150. Buteo harlani, Aud.
Early in November, 1876,1 observed a single specimen of this species sailing in easy circles at no great distance from the ground ; but, not having my gun, I was unable to secure it. — (Dresser, Ibis, 1865, 324.)
151. Buteo albicaudatus. — The White- tailed Buzzard.
Aquila coliblanca, Azara, Apunc. 1, 1803, 69. Buteo albicaudatus, Vieill.,Nouv. Diet. IV, 1816, 477 (ex Azara, I. c). — Strjokl., On. Syn. 1, 1855, 35.— Salvin, P. Z. S. 1870, 215 (Veragua). Tackytriorckis albicaudatus, Sharps, Cat. Ace. Brit. Mus. I, 1874, 162. Craxirex albicaudatus, Ridgw., Pr. Ac. Nat. Sci. Phila. 1875, 92. Buteo (Craxirex) albicaudatus, Ridgw., t. c. 98 (monographic). Spizaetus leucurus, Vieill., Nouv. Diet. XXXII, 1819, 59. Buteo leucurus, Lapr., Rev. Zool. 1849,100.
