(SWAINSON'S BUZZARD.)
[Plate XVI.]
[Illustration: BUTEO SWAINSONI.]
+Buteo swainsoni+, _Scl. et Salv. Nomencl._ p. 118; _Withington,
Ibis_, 1888, p. 469 (Lomas de Zamora); _Baird, Brew., et Ridgw.
N. A. B._ iii. p. 263. +Buteo obsoletus+, _Sharpe, Cat. B._ i. p.
184. +Buteo albicaudatus+, _Scl. et Salv. P. Z. S._ 1869, p. 634
(Buenos Ayres).
_Description._--Above blackish brown; scapulars slightly variegated
with rufous; upper tail-coverts white, tinged with rufous; tail dark
greyish brown, crossed by several ill-defined blackish bars: beneath
white or pale ochraceous; a broad band covering the whole breast
reddish brown; bill black; feet yellow; claws black: whole length
20·0 inches, wing 15·0, tail 8·5. _Female_ similar, but larger.
_Hab._ North and South America.
The figure given herewith (Plate XVI.) represents a fine adult female
specimen of this Buzzard, obtained by Mr. Frank Withington at Lomas de
Zamora, on the 4th of February, 1886, and now in Sclater's collection.
Swainson's Buzzard is a North-American species, which has only
recently been ascertained to occur in the southern part of the Western
Hemisphere. Full details concerning it are given in the standard work on
"North-American Land-birds," to which we have referred above. Messrs.
Baird, Brewer, and Ridgway divide the species into two subspecies,
"_swainsoni_" and "_oxypterus_" to the latter of which they refer the
southern specimens, but they acknowledge that it is "difficult to
express points of absolute difference" between these subspecies.
It appears from what these authorities say (_l. c._ p. 268) that a
young specimen procured by Hudson at Conchitas in 1860, and referred
by Messrs. Salvin and Sclater with doubt to _B. albicaudatus_, really
belongs to _B. swainsoni_. A second undoubtedly Argentine example is
that procured by Mr. Withington and now figured.
Like other Buzzards, _B. swainsoni_ varies much in plumage, and
occasionally assumes a melanistic form, under which it was described and
figured by Sclater in 1858 as _Buteo fuliginosus_ (_cf._ P. Z. S. 1858,
p. 356, and Trans. Zool. Soc. vol. iv. p. 267, pl. lxii.). Mr. Gurney is
of opinion that d'Orbigny's _Buteo unicolor_ is also referable to this
form of _B. swainsoni_ (_cf._ Ibis, 1889, p. 134).
A well-known writer on North-American birds (Capt. C. E. Bendire) gives
the following account of the nesting of _Buteo swainsoni_ in Arizona:--
"This species is by far the commonest Hawk in the vicinity of Fort
Huachuca, and a resident throughout the year. Lieutenant Benson found
not less than forty-one of their nests containing eggs between May 14
and June 18, 1887. These were all placed in low mesquite trees and
bushes, from 3 to 15 feet from the ground. Only six of these nests
contained three eggs each, twenty-one nests contained two eggs, the
remaining fourteen but a single egg. Many of the latter were undoubtedly
laid by birds that had been robbed before, especially where the same
nest was used again, which was frequently the case, and a few were
uncompleted sets. Two eggs is the usual number laid by these birds, in
Arizona at least. The nests were bulky platforms, composed of sticks of
various sizes, with but a slight depression in the centre, and sparingly
lined with a few bunches of dried grass. Lieutenant Benson writes me
that after the Arkansas King-birds (_Tyrannus verticalis_, Say) began to
build he invariably found one of their nests in any tree that contained
a Swainson's Hawk's nest. In one case, a pair of these birds had placed
their nest directly under, and but 8 or 9 inches from that of the Hawk.
A pair of White-rumped Shrikes (_Lanius ludovicianns excubitoroides_)
built also immediately below one of these Hawk's nests.
"When not closely looked at, many of the eggs of Swainson's Hawk appear
to be unspotted, but on careful examination there are in reality but
very few that are immaculate. Out of a series of sixty-nine specimens
sent by Lieutenant Benson there are but three unspotted ones. The
ground-colour of these eggs when fresh is a very distinct greenish
white, which in course of time fades into a dull yellowish white, even
if the eggs are not exposed to light. They are more or less heavily
spotted and blotched, varying in colour from burnt-umber to tawny olive,
and in some of the lighter coloured specimens from a French grey to a
drab-grey. Their shape ranges from a short ovate to an oval, and they
average about 2·23 by 1·71 inches in length and width."