“_Buteo borealis_ var. _lucasanus_, RIDGWAY,” COUES, KEY, 1872, 216
(under _B. borealis_).
SP. CHAR. _Adult._ General appearance of the normal plumage of var.
_calurus_, but the upper parts more uniformly blackish, and the upper
tail-coverts and tail uniform rufous, the latter without a trace of a
black bar. Beneath nearly uniform reddish ochraceous, or light rufous,
the usual abdominal belt merely indicated by a few inconspicuous spots;
no trace of transverse bars on the lower parts. _Female_ ? (No. 16,925,
Cape St. Lucas, Sept. 15, 1859; J. Xantus). Wing, 16.00; tail, 9.50;
tarsus, 3.00; middle toe, 1.60. Wing-formula 5, 4, 3, 2–6–7–8–9, 1, 10.
_Young._ Not distinguishable, by positive characters, from that of var.
_calurus_.
HAB. Peninsula of Lower California.
All adult specimens from the peninsula of Lower California agree with
that described above, in the peculiar features which I consider as
characterizing a well-marked local race. The present form is most nearly
related, in its adult dress, to the var. _krideri_ of the plains, in its
unbarred tail and immaculate lower plumage, but differs from this in
having the upper parts nearly black instead of almost white, the upper
tail-coverts deep rufous, like the tail, instead of white, and the lower
parts rufous instead of white; in the rufous lower plumage and very dark
upper parts, it closely resembles var. _costaricensis_[90] of Central
America and Southern Mexico, but the latter has a barred tail, entirely
continuous black above, plain white throat patch, and other minor
differences, besides having a quite different young plumage. As to the
young plumage of var. _lucasanus_, I cannot find any character by which
it can with certainty be distinguished from that of var. _calurus_.
Var. calurus, CASSIN.