BUTEO. 63 
therefore of opinion that the true B. borealis does not winter in any part of Central 
America, but possibly journeys to South America by way of the West Indian Islands. 
A single specimen was obtained at Santa Cruz in Patagonia by Darwin, and further 
investigations may show that B. borealis migrates with B. swainsoni into the southern 
portion of the South American continent. On this point, however, we are without 
exact information, and its winter home has yet to be correctly ascertained. 
In Western North America there is a large form which has been variously called by 
writers B. montanus and B. calurus. This bird has not apparently received a specific 
designation and we propose calling it Buteo rufescentior. It is slightly larger than the 
true B. borealis, with much more rufous thighs, but has the blackish throat of that 
species, differing from it in having a reddish patch across the lower breast and 
abdomen, on which the black spots are conspicuous. ‘This form extends from Sitka 
and British Columbia to California, and in the Henshaw Collection there are examples 
from Utah, Colorado, and New Mexico. Our collection also contains specimens from 
Zacatecas, San Luis Potosi, Colima, Jalisco, Sonora, the Valley of Mexico, Vera Cruz, 
Guatemala, and Nicaragua. 
Buteo krideri is a pale form from the Middle States of America, having the upper 
plumage mottled with white, instead of rufous, especially on the scapulars and inner 
secondaries; the under surface is almost white, with a few longitudinal streaks 
on the abdomen; the thighs are even paler than in typical B. borealis. The 
tail is of a much lighter rufous colour than in the latter species, being of a light 
cinnamon ; the black subterminal bar is either narrow or broken up, or entirely 
absent. A similar variation in this respect is often observed in true B. borealis, 
and a specimen from Illinois in the Henshaw Collection, at first sight referable to 
BL. krideri, appears to us to be an unbarred example of B. borealis, having the dark 
chestnut tail of the latter. We can trace this light-coloured race to Zacatecas, and we 
have a specimen from Ciudad in Durango, while another from the Southern Pine 
Ridge in British Honduras may perhaps be referred to B. krideri. 
The true B. calurus of Cassin is very large and dark in colour. The throat and 
abdomen are smoky brown and the chest-patch rufous, while the rufous thighs and 
under tail-coverts are also conspicuous features. The young bird has a remarkable 
appearance, being very dusky underneath and having broad bands across the thighs. 
In this immature stage the species has often been mistaken for B. harlani, and we refer 
the so-called B. harlani from Guatemala to B. calurus. The British Museum contains 
specimens of the last-named form from California and Mexico, and we possess examples 
from Zacatecas, the Sierra Madre de Nayarit, Orizaba, and Jalapa. 
Buteo lucasanus from Cape San Lucas we have not seen. It is described as a dark 
form of B&B. borealis, with no subterminal black band on the tail. Mr. Brewster, 
writing to the late Capt. Bendire (Life Hist. N. Amer. Birds, p. 216), emphatically 
refuses to believe in the distinctness of the Cape San Lucas bird, having compared 
