Field guides covering North America, in this context, include Alaska, Canada, and the Lower 48 of the United States. It does not include Hawaii, Greenland, Bermuda, Mexico southwards to the Panama Canal (which are instead covered in our neo-tropical region).
USA and Canada:
The Sibley Guide to Birds, Second Edition (Sibley). This guide covers 923 bird species, including all the regularly occurring species in North America as well as most vagrants with more than one record. Birds with only one record in the region are excluded. Since there is only one artist, there is great consistency in the (extremely high) quality of the paintings, which are both beautiful and practical. Sibley thoroughly depicts each species with separate male, female, and juvenile plumages as well as paintings of each species in flight. Concise written descriptions accompany each painting, usefully positioned near key field marks to ease identification. Range maps include separate shades for resident, summer, winter, and migratory ranges. An expanded text includes information on habitat and voice descriptions as well as tips on finding birds in the field. The team at Birding Ecotours is also glad to endorse the app (Sibley e-guide), which has all the bird calls (the “Lite” version of the app is not recommended, though).
By the way, we do not like the separate Eastern and Western versions of North American field guides because they are not substantially more practical and compact for carrying into the field than the standard versions, and we’d rather leave more space on our shelves for a foreign guide or other bird book (rather than two overlapping North American ones). It’s more convenient just to have the full Sibley guide that will cover your birdwatching whether you are in California, Kansas, or Maine.
National Geographic Field Guide to the Birds of North America (Dunn and Alderfer). The seventh edition of the National Geographic guide has recently been released and has left us impressed. The artwork is amazing, the distribution maps are top-notch, and the taxonomy is up-to-date. The Sibley guide (above) and National Geographic guide are in our opinion the two best guides for North America, with some in the office preferring one over the other.