[90] Buteo borealis, var. costaricensis, Ridgway. Buteo borealis (all citations from Central America).
Sp. Char. Adult (No. 30,409, Costa Rica; Dr. A. von Frantzius). Head, neck, and upper parts continuous, unvariegated brownish-black; whole throat white, with a few cuneate spots of black; black of the neck meeting narrowly across the jugulum; pectoral area immaculate pure white; upper part of abdomen with an imperfect belt of distinct narrow lanceolate strips of black; whole posterior lower parts fine pinkish ochraceous, unvariegated; tibiæ deepest, inclining to delicate ochraceous-rufous; upper tail-coverts immaculate rufous. Tail as in var. borealis. Wing, 16.00; tail, 9.00; tarsus, 3.20; middle toe, 1.80. Bill very high, abruptly curved. Wing-formula, 4, 5, 3, 6, 2; first, shortest.
This very curious variety is that which departs furthest from the true borealis; not only the details, but in a measure the pattern, of coloration, being greatly modified. The perfectly continuous pure brownish-black of the whole head and neck, sharply contrasted with the white throat-patch, are features which distinguish it from every other variety of this group; while the deep rufous tibiæ, and almost utter absence of transverse bars beneath, are also very distinctive characters.
The second of the two Costa Rican specimens before me (No. 33,507; J. Carmiol) differs from the type in having the white of the pectoral area clouded by an encroachment of the blackish of the neck; and across the abdomen is a deep wash of the same. The tail-feathers exhibit indications of spots along the shafts, as in var. calurus; while the upper tail-coverts have a very few bars of blackish.
Young (37,338, Tres Marias Islands, January; Col. A. J. Grayson). Similar to the adult in general appearance, but differing in the following particulars: Tail deep umber, with about twelve or thirteen narrow bands of black, and very narrowly tipped with whitish; lateral lower parts thickly spotted with blackish, and tibiæ spotted transversely with the same; lower tail-coverts with distant bars of blackish. Upper tail-coverts blackish-brown barred with white, this not touching the shaft.
Hab. Central America and Southwestern Mexico; Costa Rica, Veragua, and Tres Marias Islands (Mus. S. I.).
Localities: (?) Guatemala (Scl. Ibis, I, 217, B. borealis); Costa Rica (Lawr. IX, 133, “var. montanus”).
List of Specimens Examined.—National Museum, 4.
Measurements much the same as in the other varieties.
[91] Archibuteo lagopus (Brunn.), Gray. Falco lagopus, Brunn. Orn. Bor. p. 4, sp. 15 (1764); Penn., Gmel., Lath., Siemss., Daud., Shaw, Naum., Meyer. Buteo lagopus, Steph. et Auct. Butaëtes lagopus, Bonap., Gray, Bailly, Morr., Reich. Archibuteo lagopus, Gray, Gen. B. (ed. 2), p. 3; 1841, et Auct. (Not of American writers, nor when used for the American bird!) Hab. North and Central Europe; Northern Africa.