BIRDS— LANItDAE— COLLYRIO EXCUBITOROIDES. 
327 
COLLYRIO EXCUBITOILOIDES, Baird. 
White-rumped Shrike. 
Lani-us excubitoroides, Swainson, P. Bor. Am. II, 1831, 115.— Gambel, Pr. A. N. Sc. Ill, 1847, 200. 
g P- Cn.-^Above rather light pure bluish ash. Forehead, sides of crown, scapulars, and upper tail coverts, hoary whitish 
Beneath plain whitish. Wings and tail black ; the former with a white patch at base of primaries and tips of small quills ; the 
latter with the lateral feathers tipped with white, and this extending broadly at the base. Bill throughout pitch black. A 
continuous black stripe from the bill through and behind the eye. Length, 8.75 or 9 inches ; wing, 3.95 ; tail, 4.35. 
Hab. — Missouri plains and fur countries to Pacific coast. Eastward into Wisconsin, Illinois, and Michigan. (?) 
Head and body above asby blue, the forehead slightly hoary ; the lower part of rump and 
upper tail coverts, with the outer scapulars, almost white. Beneath pure white without bands ; 
the sides very slightly touched with ashy. Wings and tail black ; the primaries with a band of 
white at the base, showing externally as a patch in the wing ; the white extending obliquely a 
little further on the inner than the outer web. The tertiaries and secondaries are paler on the 
outer portion of the inner web towards the base, but not abruptly white. The secondare 0 , 
tertials, and inner primaries tipped with white. All the feathers of the tail, except the 
innermost, are tipped with white, the amount diminishing from the exterior ; the outer feather 
is, in fact, entirely white, except a patch an incb long on the inner web covered by the tail 
coverts, and there is a white patch at the base of all the others, except the middle. A narrow 
band on the forehead, including the feathers along the base of the bill, and passing backwards 
over the lores, eyes, and auriculars, black, this color involving the upper eyelid. This is 
bordered above by a hoary tinge in the gray of the crown. 
The young differ chiefly in a strong tendency to waved, dark lines in the plumage of the 
upper and under surfaces. There is also a decided indication of reddish brown in the ground 
color. The female is smaller, and sometimes has the under mandible paler at the base. 
This species is similar in appearance to G. ludovicianus, but differs in several points. The 
ash of the upper parts is decidedly lighter, the rump generally almost white, instead of nearly 
like the back. The white at the base of the tail feathers is much more extended, reaching 
within half an inch or less of the tips of the coverts. There is also a good deal of white on 
the secondaries, visible from below, not seen in ludovicianus. 
In a large series of specimens I find differences, which, however, I can scarcely consider as 
specific. There is some variation in the ground color, but this is almost always lighter than 
in 0. ludovicianus. The boary tinge on the forehead and alongside the crown is sometimes 
entirely wanting ; and in the most strongly marked specimen (from Presidio) the under parts 
are strongly tinged with ash. The amount of black on the outer tail feather is sometimes but 
little more than in ludovicianus. Sometimes the black band across the base of the bill is 
distinctly visible, at others it is wanting, leaving the boary bluish of the head. 
The specimens before me from Wisconsin and Michigan are all immature and not well 
characterized ; I am, however, inclined to refer them to G. excubitoroides. An adult, No. 101 l 72, 
however, from soutb Illinois, is exceedingly like specimens from the plains, except that the 
rump is not quite so whitish. 
In the collection of the Philadelphia Academy is a shrike collected in California by Dr. Gambel, 
which exhibits some peculiarities. The ash color above is darker than in excubitoroides, and there 
is no hoary on the forehead and sides of the crown at all. The tail coverts are very nearly the 
color of the back, not whitish. The black of the sides of the bead extends further down, to a 
