502 LAND BIRDS 
In several nests, May 20, when the watch began, the 
young were nearly ready to fly, and their little heads 
were stretched over the edge as if they were trying to . 
gather up courage to make the dive. In other cases the 
broods were much later. Incubation required twelve 
days, and in this the male shared equally with the 
female, seeming fully as much at home on the nest as 
did she. It was delightful to see them sit side by side 
on the edge, turning their little blue heads sidewise as 
they peeked into the cradle and talked it all over to- 
gether in low sweet twitters. And when the nestlings 
were finally hatched, one need not climb to discover the 
fact, for the busy importance of the happy housekeepers 
told all who had eyes to see. The young were fed by 
regurgitation until two weeks old, and then the diet 
was varied by an occasional large insect that looked like 
a bluebottle fly. 
614. WHITE-BELLIED SWALLOW, OR TREE 
SWALLOW. — Tachycineta bicolor. 
Famity. — The Swallows. 
Length: 5.00-6.25. 
Adult Male: Upper parts iridescent steel blue ; lores deep black ; wings 
and tail blackish, slightly tinged with greenish; under parts pure 
white. 
Adult Female: Similar to male, but upper parts duller. 
Young: Upper parts dull brownish slate. 
Geographical Distribution: Whole of North America, migrating in winter 
to the Gulf States and West Indies. 
California Breeding Range: Chiefly in upper Sonoran zone, west of the 
Sierra Nevada. 
Breeding Season: May, June, and July. 
