BOOKS
The Sibley Field Guide to Birds of Western North America by David Allen Sibley
Peterson's Field Guide to Birds of Western North America by Roger Tory Peterson
WEBSITES
Very comprehensive ID information on birds of North America managed by the Cornell Lab of Ornithology. Photos to help you with ID, even audio recordings of birds' songs.
Includes a Guide to North American Birds with, of course, wonderful illustrations by John James Audubon, news on birds, conservation, climate.
Website of the California Native Plant Society packed with advice about what to grow to create a nave habitat for birds and butterflies, managing pests, where to buy natives, and how to conserve water.
Wild Birds Unlimited may be a commercial organization but their website has very informative pages on Backyard Birds and Bird Behaviors. Also advises on deterring rodents.
APPS
Merlin Bird ID by Cornell Lab of Ornithology.
A quick and easy way to find the bird you've seen in the field, females and immatures included, as well as their songs and maps showing seasonal locations.
iBird Pro Guide to Birds
Not cheap but very comprehensive with detailed information about bird coloring and behavior.
Audubon Bird Guide: North America