Chapter III: GENUS HYPOTRIORCHIS. Boie Isis, p. 976. (1826.)

DENDROFALCO. Gray list, p. 3. (1840.)

Size small, tarsus lengthened and rather slender. In all other characters much like typical Falco. Toes long, slender and furnished with sharp, curved claws. This genus includes about ten or twelve small species found in various parts of the world, and for the greater part dark colored, like the species of typical _Falco_.

1. Hypotriorchis columbarius. (Linn.) The Pigeon Hawk.
Falco columbarius. Linn. Syst. Nat. I. p. 128. (1766.)
Falco intermixtus. Daudin, Traité d’Orn. II. p. 141. (1800.)
Falco temerarius. Aud. B. of Am. I. p. 381. (1831, plate pub.
1829)
“Falco æsalon. Temm.” Rich. and Sw. Faun. Bor. Am. Birds, p. 37.

Cat. Car. pl. 3. Vieill. Ois. d’Am. Sept. pl. 11. Wils. Am. Orn. II. pl. 15, fig. 3. Faun. Bor. Am. Birds, pl. 25. Aud. B. of Am. pl. 75, 92. Oct. ed. I. pl. 21. De Kay, Nat. Hist. N. Y. pl. 4, fig. 9.

Small, head and body broad and strong, bill short, wing pointed with
the second and third quills longest, tail slightly rounded, tarsi and
toes slender. Adult male. Entire plumage of the upper parts dusky
slate color, inclining to bluish, every feather with a black
longitudinal line. Forehead and throat white, other under parts pale
yellowish or reddish white, every feather with a narrow longitudinal
stripe of brownish black, plumage of the tibia, light rusty red, with
narrow stripes of black. Quills black, with transverse bands of white
on their inner webs, and narrowly tipped with ashy white, tail above
light bluish cinereous tipped with white, and with a wide subterminal
band of black, and with several other narrower bands of black, inner
webs nearly white. Cere and feet yellow, bill blue.

Middle age or winter plumage? Entire upper plumage, brownish black,
slightly mixed with rufous on the head and neck behind, white of the
face, and under parts more deeply tinged with reddish yellow, dark
stripes wider, plumage of the sides, with wide transverse bands of
brownish black, predominating on some feathers, and the yellowish
white, assuming the form of circular spots. Tail dark brown, nearly
black tipped, and with four bars of white, upper tail coverts with
spots of white at their bases. Feet yellow.

Younger and adult female? Entire upper plumage, dusky brown, quite
light, and with a tinge of ashy in some specimens. Head above with
narrow stripes of dark brown and rusty red, and in some specimens,
many irregular spots and edgings of the latter color, on the other
upper parts. Forehead and entire under parts white, with longitudinal
stripes of light brown. Plumage of the sides and flanks light brown,
with pairs of circular spots of white, tibia white, with dashes of
brown, tail above and below pale brown, with about six bands of white.
Neck behind with a distinct band of white.

Dimensions. Total length (of skin,) females, 12 to 14 inches, wing, 8
to 9, tail, 5½ inches. Male. Total length, 10 to 11 inches, wing, 7½
to 8, tail, 5 inches.

Hab. North and South America. Wisconsin, (Dr. Hoy.) California, (Mr.
J. G. Bell.) Oregon, (Col. M’Call, Dr. Townsend.) Cuba, (M. de Sagra.)
Jamaica, (Mr. Gosse.) New Granada, (M. Parzudaki.) Bermuda, (Sir. W.
Jardine.) Spec. in Mus. Acad. Philada.

Obs. The adult of this species is with difficulty distinguishable from the European _H. æsalon_, but we have never seen the latter in the nearly black plumage, which we regard as characterizing the young or winter plumage, of the American bird. The light, “liver brown” plumage, represented by European authors as the female of _F. æsalon_, frequently occurs in this bird, and is given by Rich. and Swains. in Fauna Boreali Americana, Birds, pl. 25. The adult which appears to be _Falco temerarius_, Aud., is figured in B. of Am. pl. 75, the other figures by Aud. pl. 92, and Wilson’s plate, represent this bird in the dark plumage as described above.

Adult specimens from Western America, even more closely resemble the European species, but differ from the Eastern American only in small and scarcely describable particulars, as the slightly greater extent of the white front, or the greater purity of the white of the throat and breast. We regard the stage of plumage above described as that of the female, (and as figured by Rich. and Swains.) principally on account of its analogy to the female of the nearly allied European species.

This bird is of frequent occurrence in the United States. The largest specimens that we have ever seen are from Oregon, and may prove to be of a distinct species, though we cannot at present, determine.