Localities quoted: (?) Xalapa (Sclater, P. Z. S. 1859, 368); Oaxaca (Scl. P. Z. S. 1859, 389); (?) Cuba (Cab. Journ. II. lxxxii; Gundl. Rep. 1865, 223; resident. “B. borealis”); S. E. Texas (Dresser, Ibis, 1865, 324).
LIST OF SPECIMENS EXAMINED.
National Museum, 44; Philadelphia Academy, 18; Boston Society, 6; Coll. G. N. Lawrence, 2; R. Ridgway, 5. Total, 75.
| Sex. | Wing. | Tail. | Culmen. | Tarsus. | Middle Toe. | Specimens. |
|---|---|---|---|---|---|---|
| ♂ | 13.50–16.00 | 9.50–10.00 | .90–1.10 | 2.90–3.30 | 1.70–1.80 | 30 N. Am. |
| ♀ | 16.00–17.25 | 9.50–11.30 | 1.00–1.08 | 3.30–3.40 | 1.80–1.95 | 16 N. Am. |
| ♂ | 13.25–14.00 | 9.00–0.00 | 1.00–0.00 | 3.30–0.00 | 1.80–0.00 | 2 Jamaican. |
| ♀ | 14.50–0.00 | 9.00–0.00 | 1.10–0.00 | 3.25–0.00 | 1.75–0.00 | 1 Jamaican. |
| ♂ | 15.50–0.00 | 9.50–0.00 | 1.15–0.00 | 3.10–0.00 | 1.85–0.00 | 1 Cuban. |
A large collection of specimens of this race presents a series connecting borealis with the black form known as “calurus”; every possible condition between the two being indicated in the range of individual variation. The lightest styles as distinguished from var. borealis always have the tibiæ barred with rufous; the crissum, also, is generally barred, on the throat the blackish-brown predominates, and the tail has more or less perfect bars to the roots of the feathers; generally, however, these are merely indicated by projections from the shafts.
The extreme condition of this is the melanistic form which Mr. Cassin described as “Buteo calurus”; the darkest example of which (5,481, Petaluma, Cal.; E. Samuels) is entirely blackish-brown, wings and scapulars with feathers somewhat paler at tips; breast inclining to dark sepia-brown, the feathers with black shaft-streaks; tibial feathers faintly tipped with pale grayish-brown; lower tail-coverts tipped and barred with rufous; upper tail-coverts deep rufous barred with black; tail deep chestnut-rufous, the subterminal black band very broad, and anterior to this are nine or ten imperfect narrower black bands.
These fuliginous examples have always a more or less appreciably lighter pectoral area, corresponding to the white of this region seen in the lighter styles.
Of this race, almost each individual has its own characteristic markings, and scarcely two are to be found alike in a very large series from Western North America. All the specimens from the Rocky Mountains to the Pacific, and from the table-lands of Mexico, as well as from Cuba and Jamaica, are referrible to this variety, although we are not aware that in the latter region the bird ever becomes black. In the latter island this species (as is also the case with many other birds) seems to be remarkably subject to albinism. In the peninsula of Lower California it is replaced by the var. lucasanus, and in Central America by the very different var. costaricensis; from both of which it may be distinguished by the numerous transverse rufous bars crossing the posterior under parts, which character serves also to distinguish the lightest examples from the eastern typical borealis.
A specimen (50,761; Colonel Grayson) from the Socorro Island, S. W. Mexico, is like some Fort Tejon specimens.