[jedigrant]

North America

The Sibley Guide to Birds - by David Allen Sibley. Still my favorite. Runner up goes to the latest NatGeo guide

I agree with the suggestions for Costa Rica and West Indies. For Panama, I'd go with Angehr and Dean.

South America is especially tough, since you almost have to go with (at least) one guide for each country.

[J. Moore]

Best Bird ID Reference: agree with The Sibley Guide to Birds--second to none on ID issues. Too big to be considered a true field guide though, and text is sparse on anything but ID issues and not enough text for beginners.

Best Regional Guides for the Field: The Sibley Guide to Birds of Eastern North America and The Sibley Guide to Birds of Western North America. Among the lightest and most compact guides available, yet quite comprehensive. Also have more text, so better for beginners. Not as many plumages illustrated as the "big Sibley" though, so these are not a replacement for it.

Best and Most Comprehensive Photo ID Reference: The Stokes Field Guide to the Birds of North America (2010); Honorable Mention to The Crossley ID Guide: Eastern Birds (2011). All are too heavy to carry in the field though.

Best Pocketable Guide Covering all of N. Am. (north of Mexico): 6th Ed. National Geographic (but it's a bit heavier than I prefer for a portable guide)

Jim