White-rumped Shrike 431 
this species. He found the nests usually placed in low 
bushy thick-twigged willows at from seven to twenty 
feet from the ground. The nest is a bulky, rather untidy 
structure of grass and other vegetable stems, lined with 
finer material, including wool and hair. The eggs, 
seven or eight in number, are whitish-yellow, uniformly 
freckled with yellowish-brown, and measure about 
“97 X *72. 
Family VIREONIDA. 
Bill variable in size, but rather Shrike-like, strongly 
hooked and notched ; nostril oval or rounded, overhung 
by an operculum ; frontal and rictal bristles present ; 
wing with ten primaries, but the outer or tenth sometimes 
so small and rudimentary as to be entirely concealed, 
sometimes about half the length of the ninth; tarsus 
longer than the middle toe and claw, scutellate in front ; 
toes adherent at the base, the basal joint of the middle 
toe rather shortened and soldered to the basal joints 
of the lateral toes; plumage with plain green and grey 
prevailing ; never spotted or barred even in the young. 
This is a purely New World family, containing the 
Vireos or Greenlets ; about seventy species are known ; 
those of North America were formerly all referred to the 
type genus, but it is perhaps a matter of convenience 
to divide them as is here done. 
Key oF THE CoLoRADO SPECIES. 
A. Tenth primary entirely concealed, apparently absent; no 
wing-bars. V. olivacea, p. 432. 
B. Tenth primary narrowed, pointed and short, less than } 
length of the ninth. 
a. No wing-bars. V. g. swainsoni, p. 433. 
b. Two distinct pale wing-bars. 
a? ‘Olive-green above and on the flanks and edges of the 
wing. L. s. cassini, p. 435. 
b? Grey above, edges of wing whitish. L. s. plumbeus, p. 435. 
