The Sibley Guide to Birds East and West were both published in April 2003.
They use the same artwork from the original Sibley Guide to Birds. These employ a different design, with each page divided into top and bottom halves, and the species information fit into that space. No changes were made to the artwork, but fewer illustrations are used in these smaller books. The text was largely rewritten. The largest differences being that the voice descriptions are cut, and a sentence or two was added to each species describing the general status and habitat.
The maps were completely revised for these books, using a team of over 100 experts from around the continent, compiled by Paul Lehman