Here's my review of the 2005 (6th) edition.
+ Easier to use than previous edition, better photos and color register
- Some photos omitted from previous edition were helpful for identification, still some disorganization
This new edition is a great improvement over the 5th. Entries cover 141 species and subspecies. Birds are still organized by habitat, but page headers and color coding make finding a bird much quicker, which is useful for field identification. Symbols showing endemic, indigenous, alien, visitor, and endangered species are clearer. The endemic bird list and distribution maps have been updated, as have references and descriptions (for example, this edition notes the split of the African Silverbill [Lonchura cantans] from the Warbling Silverbill [Lonchura malabarica]). Each entry includes 1-2 photos (many of higher quality than in thge previous edition), the common name, Hawaiian name, genus and species (plus subspecies where relevant), distribution, description, voice, and habits. The "voice" and "habits" sections are especially helpful for differentiating between birds of similar habitat and appearance. A collection of island maps in the back provide a quick reference for common birds.
Although the color-coded tabs make the book much more usable, it's still not clear what determined the order in which birds appear within each section. It is the same as in the 5th edition and is not alphabetical by common name, Hawaiian name, or genus; it also is not in order of relative frequency. While I appreciate most of the new photos, and particulatly those of juveniles, some omissions are puzzling. For example, the 5th edition had a nice photo of a White-tailed Tropicbird from above, showing the black markings on its wings that help differentiate it from the Red-tailed Tropicbird when it is at a distance and the tail color can't be seen. This was especially useful since viewing opportunities at Kilauea Point and Waimea Canyon are often fom overhead and at a distance. The 5th edition also included a facing page photo of an immature Red-tailed Tropicbird, illustrating the description of "heavy black barring on upperparts" (5th ed., p. 16). This photo is omitted from the 6th edition. Thus, there is now a notation of the juvenile Red-tail's "heavy black barring" and the adult White-tail's "black marks on wings and back" but no photo of either to guide the reader. Since the text notes that a third species, the Red-billed Tropicbird, has recently been seen at Kiluea Point, and that it has "heavily barred upperparts," the identification is muddier still for those not already familiar with the three species.
If I were in charge of the the 7th edition, I would organize each section by main color or by most-to-least common, include a photo of an immature bird when this aids differentiation, include a colored notation by each bird identifying the islands on which it is found (to supplement the text and the endemic checklist in the back), and move birds presumed to be extinct or exceptionally rare to a new section.
This field guide is useful for quick identifications of the expected birds; less so for visitors. It has the virtue of large photos and is small enough to carry easily. For more comprehensive coverage, spring the $45 for Pratt et al.'s A Field Guide to the Birds of Hawaii and the Tropical Pacific. Yes, it's woefully out of date (it was last revised in 1987), but it provides illustrations of juvenieles and adults of both sexes, side-by-side species, and a broader geographic range. Pratt's newer Enjoying Birds and Other Wildlife in Hawai'i (revised 2002) is light on bird photos but heavy on viewing sites, species lists, and information. It includes military bases and atolls; you can't get there from here but it's still interesting to know. It could be heavier on "other wildlife" (a 4-page sop rather than a real focus; on my last trip I saw butterflies, other insects, an amphibian, a reptile, and a nice big spider that aren't represented here).
Of the 141 birds represented in the Audubon book, we saw 40-41 (one identification still pending) in 4 days this month, one at the airport on O'ahu, the others on Kaua'i at Kilauea Point NWR, Hanalei NWR, Waimea Canyon SP, Koke'e SP, Alaka'i Wilderness and along the Kuhio and Kaumuali'i highways, as well as outside the hotel.