BIRDS AQUILINAE — POLYBOKUS THAEUS. 
45 
appreciable specific differences between specimens from all parts of North America, and we may- 
be allowed to add, very slight between those of this country and of Europe and Asia. 
List of specimens. 
Catal. No. 
Sex and age. 
Locality. 
When collected. 
Whence obtained. 
Original No. 
Collected by — 
Measurements. 
Length. 
Extent. 
Wing. 
4366 
5837 
6872 
4616 
6844 
3 
Ft. Steilacoom, W.T 
do 
May, 1855 
Oct. 2, 1856 
Mr. Geo. Gibbs 
Dr. Geo. Suckley.. 
Lieut. Williamson . 
181 
589 
23.00 
22.25 
64.50 
64.50 
19.50 
Colorado river, Cal. 
Ft. Fillmore, N. M. 
Major Emory 
POLYBORUS, Vieillot. 
Polyborus, Vieillot, Analyse, p. 22, (1816.) 
Smaller than in either of the preceding genera of eagles. Bill rather long, compressed ; cere large ; wings long, pointed ; 
tail moderate or rather long ; tarsi long, rather slender ; claws long, rather weak, and but slightly curved ; space in front of 
and below the eye naked. 
Two species only form this genus, both of which, in their habits and manners, show an 
approximation to the vultures. They are well known birds of South America. 
POLYBORUS THARUS, Molina. 
The Caracara Eagle ; The Mexican Eagle. 
Falco tharus, Mol. Sagg. Stor. Nat. Chili, (1732.) 
Falco cheriway, Jacquin, Beyt. Gesch. der Vog. p. 17, (1784.) 
Falco brasiliensis, Gm. Syst. Nat. I, 262, (1788.) 
Falco plancus, Filler, Cimelia Physica. 
Polyborus vulgaris, Vieill. Nouv. Diet. V, 257, (1816.) 
Figures . — Vieill. Gal. I, pi, 7 ; Swains. Zool. 111. I, pi, 2 ; Gay's Chili, Orn.pl. 1 ; Aud. B. of Am. pi. 161 : Oct. ed. I, pi. 4. 
Legs rather long, occipital feathers somewhat elongated. Mult. — Head and body above and wide belt on the abdomen and 
tibia brownish black ; neck, breast, upper and under tail coverts yellowish white, on the breast with narrow transverse bands 
of black. Tail white at base, with numerous transverse bands of black and widely tipped with black ; bill bluish tipped with 
yellowish white ; legs yellow. 
Younger. — Head and body above dull brown, darker on the head, and many feathers having paler edgings ; under parts dark 
brown, with longitudinal stripes of dull yellowish white ; throat dull white ; tail for the greater part and its coverts above and 
below white with numerous transverse bands of ashy brown, and tipped with brownish black. 
Total length, female, about 25 inches ; wing, 17 inches ; tail, 10 inches. 
Hab.— Southern North America. Florida. Texas. Mexico. Spec, in Nat. Mus. Washington, and Mus. Acad. Philadelphia, 
One of the most abundant of the rapacious birds of South America. It is of frequent 
occurrence also in Mexico and Texas, and is found also in Florida. This bird is more sluggish 
in its habits than is usual in this family, and may belong more properly to the family of 
vultures. It subsists mainly on dead animals, and walks on the ground with facility. 
