570 NORTH AMERICAN BIRDS. 
about 4.10-4.50, wing 1.85-1.95, tail 2.10-2.25. Hab. Western 
Mexico (Mazatlan to Tehuantepec). 
P. nigriceps Barrp. Baird’s Gnatcatcher.! 
d@. Lores, superciliary region, and greater portion of ear-coverts 
white, in abrupt contrast with black or gray of top of head; a 
distinct black or gray streak behind eye, along upper edge of 
ear-coverts; length about 4.00-4.50, wing 1.80-1.90, tail 1.70- 
1.85. Hab. Guatemala to Peru and Venezuela. 
P. bilineata (Bp.). White-browed Gnatcatcher.? 
a. Exposed portion of inner web of outer tail-feather with at least the basal half 
black. 
db. Adult males with top of head glossy black. 
ce. Outer tail-feather with outer web entirely white, the inner web broadly 
tipped with white. 
Adult male: Above light bluish gray (as in P. cerulea), the whole 
top of head, down to lores and auriculars, uniform glossy black ; 
eyelids white ; lower parts white, shaded with bluish gray on 
sides. Adult female: Top of head wholly gray, the plumage 
otherwise as in male, but usually somewhat duller. Young: 
Similar to adult female, but somewhat washed with brown- 
ish—the young male attaining the black by degrees, com- 
mencing with a streak over each eye. Length about 4.25- 
4.60, wing 1.90-2.00, tail 2.15-2.25. Eygs 54.42. Hab. 
Southwestern border of United States, from southern Texas 
to lower Colorado Valley, and thence south to Cape St. Lucas; 
northern Mexico. 
752. P. plumbea Bairp. Plumbeous Gnatcatcher. 
ce, Outer tail-feather with outer web black, edged with white, the inner 
web narrowly tipped with white. , 
Adult male: Top of head black, as in P. plumbea, rest of upper 
parts dark bluish gray or slate-gray ; eyelids white ; lower parts 
dull light gray, deeper laterally, tinged with brownish poste- 
riorly. Adult female: Similar to male, but with black on head 
wholly replaced by the general dark gray color, the latter duller 
than in male. Young: Similar to adult female, but more tinged 
with brownish—the young male with black of head appearing 
gradually, asin P. plumbea. Length about 4.15-4.50, wing 1.90- 
2.00, tail 2.15-2.25. Hab. Pacific coast of southern California 
and northern Lower California. 
753. P. californica Brewst. Black-tailed Gnatcatcher. 
b*. Adult male with top of head ash-gray, like back. 
Adult male with a curved black line bordering upper and hinder mar- 
1 Polioptila nigriceps Barrp, Review Am. B. i. 1864, 69. 
* Culicivora bilineata Br., Consp. i, 1850, 316. Polioptila bilineata Scr, P. Z. 8. 1855, 12. 
