GREEN, GREENISH GRAY, AND OLIVE 481 
Geographical Distribution: Lower California, Southern California, <Ari- 
zona, and Western Mexico. 
Breeding Range: In southern part of California, both east and west of 
the Sierra Nevada, 
Breeding Season: On desert side of mountains, breeds in February; on 
the coast side, in May. 
Nest: Of plant down or fine shreds of vegetable fibre; lined with 
feathers, and covered with lichen, bark, and leaves; fastened in 
place by spider web. On bushes, 1 to 6 feet from ground. 
Eggs: 2; white. Size 0.48 X 0.31. 
THE Costa Hummingbird is a haunter of the desert 
plains and barren mountain ranges of Southeastern Cali- 
fornia, where it nests in the branching cactus. On May 
16 a nest containing one egg was discovered on a low 
branch of a willow five feet from the ground. The 
mother was brooding, and refused to leave until forced 
to do so. The next morning there were two tiny white 
eggs. Incubation lasted thirteen days, the young emerg- 
ing from the shell on the twenty-ninth. At first they 
were very tiny, naked, grayish bits of bird life with black 
skinny knobs for eyes, more like worms than humming- 
birds; but they grew surprisingly fast, and at the end 
of the fourth day were covered with yellowish white 
down on their backs and tops of their heads. By the 
sixth day this had spread to the wings and rump, the 
edges of the former began to show dark lines of needle- 
like points where the pinfeathers were coming through. 
On the eighth day they had more than quadrupled in 
size, were darker in color, and were commencing to push 
pinfeathers through the down. On the twelfth day they 
seemed like miniature adults, for they were covered with 
greenish feathers, the hair-like down still sticking out in 
spots on the crown and back, but the plumage showing 
