I thought this was to be a straight-forward book review, but rarely has an assignment caused such a reevaluation of the basic understandings and definitions that have been a key part of my hobby and career. Don’t worry: this is not going into deep philosophy, but this review necessitated determining in my own mind not only what a bird (and tree) guide should be, but also how this has fundamentally changed in the nearly six decades that I have been a birder.

When Frank Izaguirre first asked, I thought the assignment was to be a review of a new field guide. I quickly said yes, but then added that I was not a big fan of photo guides. But then, right there in the first email, I started back-peddling: Well, I really do like the Stokes Guide, which is great, and yeah, I am a big fan of the iconoclastic Crossley Guides, and so on. But then, after I hit send and backed away slowly from the computer, I began to reflect on just what a modern “bird guide” needs to be. These were unfocused thoughts until the moment that the 907-page National Audubon Society Birds of North America landed (with a thud) on my front stoop. Then it was no longer an esoteric question, but a real challenge.

Since I hadn’t really thought about the essence of a bird guide in a few years, a real rethinking was about to begin, focusing on the prerequisite needs and differences of a field guide versus a reference guide. I see few birders today carrying a physical book field guide, and if they are, they are predominantly of an older generation. For the vast majority, it is all on their smart phones: photos, drawings, vocalizations, maps, apps, camera, and recent sightings. If all else fails, there is always Merlin Bird ID to make the call.

I never carry a field guide today, nor a smart phone with birding apps. This is not elitist in any way; it’s not that I know everything, just that I have always regarded field guides as references to study and learn, as preparation, not a crutch. I am of the school wherein if you see a bird you don’t know: study it, take notes, take photos, make sketches. The time to consult the guide is when you get back to the car, or get back to the house. My field guides (I have them all) have always been strategically placed around the home, next to my desk, bed, dining room table, even in “the reading room.” They are ready references that have mostly never seen the field. Even when traveling to exotic locales (remember traveling?) where every bird is new, such as a pre-2020 visit to Canopy Camp, the Panama field guide was feverishly studied over pre-dawn coffee or post-dinner at the end of a wonderfully exhausting day. But in the field, why be looking down at a guide when you can be looking up? And, you don’t need a field guide to identify a Harpy Eagle! I make no admonitions or value judgements here, and I know this approach is not for everybody, but that is how I bird.

So this was the conundrum I now faced: what was a field guide in the past, and what is a field guide twenty-one years into the 21st century? At times the lines are blurred, but at some point in the last two decades, it does seem that field guides have morphed into reference guides, a process that began with The Sibley Guide to Birds in 2000. When the National Audubon Society Birds of North America arrived, the cover announced that it was “the complete guide to birding,” which didn’t really help in classifying it. I quickly realized that it was not a field guide. It was too big, too heavy to carry even if you are so inclined. It was too detailed, showing too much information. Definitely a reference guide, yet here were descriptions, similar species, in-depth ID points, and well-organized photos for comparisons. In some ways, it seemed more like a field guide. Could it be both a field and reference guide at the same time?

Part of what we expect in a field guide, or a reference guide, is a generational thing. I grew up with the Peterson guide, A Field Guide to the Birds, Second Edition (1947), that my grandmother gave me when I was 12. It still holds an honored place on the bookshelf today, faded, dog-eared, pages falling out (I certainly used to carry my guide into the field). I remember thinking when I first opened it that there was simply no way I could ever possibly see all these birds. But the date was October 6, and the place was Stone Harbor, just north of Cape May, and the next day the first bird I identified with my new Peterson was a Black-and-white Warbler in our seashore yard. And with the cockiness of youth, I remember thinking that just maybe I can see all these birds! (I haven’t yet, but I’m still trying.) On the other hand, my reference guide in those early years was National Geographic Society’s Water, Prey, and Game Birds of North America by Alexander Wetmore (1965). But I digress….

But with this perspective, I am somewhat biased as to what a field guide should be, as opposed to, or in concert with, what a reference guide should be. Part of a book review is figuring out how and if a book will fill a needed niche, and here you need to first figure out what that niche is. It is hard to slot the National Audubon Society Birds of North America. There is no easy pigeonhole. This is not necessarily bad—some great works in all fields, literature, music, art, cooking—blend the lines. Crossover hits are valued in all fields, as they blend genres and attract diverse audiences. Single target or many targets? I am sure that the editors at NAS and Knopf hashed over these questions many, many times. There is no right or wrong in different approaches. Like in your choice of houses, cars, clothes, optics, we make a personal choice in our bird guides, whether field or reference, for those aspects that fit your comfort level, style, utility, durability, and ease of use. No one size fits all, but certainly in publishing there is a tendency to try to cover many bases and reach out to a wide audience. This is the challenge, and sometimes dilemma, for all editors and publishers. For one thing, NAS and Knopf have cornered the market, or at least set the bar very high, with the NAS Sibley Guide to Birds. Few would argue that the Sibley Guide to Birds has set the modern standard for field guides, and maybe even reference guides. It is a tough act to follow. So what was this committee aiming at? I say committee, because there is no author, or even an editor, listed for the NAS Birds of North America. This was the question at the forefront as I opened this impressive and formidable book.

First of all, it is a BOOK! This is a wonder in its own right in this day and age of large and small bookstores closing, shrinking libraries, and societal focus on blogs, podcasts, and reliance on internet sources and artificial intelligence. And I won’t even go into the disinformation age. Second of all, it is a book of high quality. It is attractive, well designed, user-friendly, well put together, durable. The cover, the paper, the printing and the color balance are as good as it gets (not a guarantee in publishing and printing). The binding seems strong and permanent, also not a given. I liked the color-coded margins for quick and easy reference. A minor thing maybe, but I love the ribbon page marker. Maybe it’s a throwback, but a nice touch for this old-fashioned reader. The book is solid. The physical quality makes it well worth the price. If I first blinked at the $49 price tag, well, I have to remember that this is an average and competitive price in this day and age. I am curious though what my grandmother paid for my priceless Peterson back in 1961.

There are many good points. The arrangement is well thought out, and the layouts work well. 800 species are covered, with 700 range maps. Only vagrants (rarities) don’t get a map, but the text nicely references where they hail from. The range maps are excellent, brighter, bolder, and much more easily read than in many guides. The conservation status of each species is shown, based on the designations given by the International Union for Conservation of Nature’s Red List of Threatened Species. This approach is accurate on the global scale, but is a broad-brush approach that is not always appropriate for North America. For example, Fulvous Whistling-Duck’s listing of LC, or Least Concern, may be accurate on the international scale for this cosmopolitan species, but this bird has seen a major decline in North America. The above said, for many species (including the Fulvous) you will find exemplary discussion on conservation status and issues, often on a regional level.

The introductory section is very well done, readable, spot-on. It contains biology, behavior, intelligence of birds (a current hot topic), bird feeding, and ethics. These topics cover a lot of ground, and as a result they are succinct, yet are very well written by well-known birders and ornithologists. Essays on bird biology topics are a nice touch, and are again penned by top experts in their fields. One thing I particularly liked in the introductory material was the good explanations of terms that long-time birders will be familiar with, yet might be unknown to newcomers. As a bird walk/tour leader, I can sometimes be guilty of assumptions, pointed out by participants’ questions such as: “What do you mean by plunge-diving?” “Hawking insects?” “You said the birds are dancing?” Whoops! Remember the basics. So I like these explanations up front, although there is a full glossary at the back of the book too. There is one curious omission: despite the terrific explanations and glossary, nowhere to be found is an illustration of the anatomy of a bird. I don’t think I have ever seen a field guide or a reference guide without an anatomy diagram. Almost every reader will probably have this in other books, but this is something odd to need to cross-reference. The bird families section is excellent, covering a subject not readily understood by many birders, and a good tool to have in your tool kit. The section is exemplary, but it needs just one more paragraph linking families to the classification and taxonomy section that inexplicably fails to mention families. It is a minor glitch maybe, but one that could be confusing to some.

Despite an excellent text, the photographs are the heart and soul of Birds of North America. There are an amazing 3,500 high quality color photographs in these 907 pages. My only real concern/issue with this monumental effort is some of the photo selections. For a number of species, the images do not depict the bird particularly well. This is an issue dear to me; over the years I have been tasked with being the photo editor for several books, and I respect that this is a herculean task. Much of the issue is far bigger than NAS’s efforts here. I have repeatedly found that photographers always, and totally understandably, submit their best shots, with “best” being defined as sharpest focus, best lighting, in-your-face close-ups (or crops), and showing dramatic attitudes or behavior. This can work well for coffee table books, but not so much for a field guide or a reference when you really need to have a photograph that captures the shape and essence of the bird—a photo that looks like the bird. In my limited experience as a photo editor, I have had to reject many fantastic shots, and get back to the photographer: “Say, do you have anything else that looks more like a Ferruginous Hawk, you know, that captures the GISS of a Ferruginous? That shot of it catching the ground squirrel is truly amazing, but...” I have asked for uncropped original images too, as a point-blank cropped image might well display different features and field marks than you actually see during real-world conditions in the field.

Understand that this NAS guide has many truly fantastic photos for almost all species. But presuming that the “committee” (not editor) wanted this guide to do double duty, some of the photos could have been chosen better. Many images are excellent, yet not diagnostic. For example, there are five photos of Dovekies included, but all sitting on rocks on the breeding grounds. I would bet that 99% of Dovekie sightings by 99% of birders are of birds sitting on the water (seen from a boat), or fly-bys while scanning from a wind-swept headland. Another example: among five images of adults, why not show a single juvenile Laughing Gull instead of birds copulating or nest building? For Red-throated Loon, every image shows the stunning breeding plumage that they only retain for a few weeks when on the breeding grounds. Of the many tens of thousands of Red-throated Loons I have seen on migration and wintering in New Jersey, I can count on two hands those that have shown the red-throated breeding plumage. Why not one image of the prevalent basic (“winter”) plumage? For Red-tailed Hawk, not one photo readily shows a red tail, nor do the Northern Harrier images clearly show the diagnostic white uppertail coverts. For Rough-legged Hawk, four of the six images show birds taking off, flaring, and pouncing, yet not one shows a good, diagnostic image of the classic plumage or profile of a soaring Rough-leg. The prize-winner for a curios photo choice is of an Osprey carrying a bird.

The faint criticism above does not relate to the whole book or all birds. I find that songbirds in general are much better in comparison. As an example, I thought that all the vireos were exceptional, very well depicted, and maybe better than can be done in a field guide with drawings/paintings. The photos chosen here are masterful, and reflect an enlightened and talented photo editor. I suspect, but do not know, that the committee approach of NAS with this guide also translated to several photo editors, leading to some disparity in style and what was chosen and depicted. These photo issues may be of limited concern in the grand scheme of the book, but I can’t help but feel that the committee approach may have led to missing the chance to do so much more, and for many species (not all) preventing the guide to realize the double duty of being a true and usable field guide as well as a reference guide.

Of interest is that the photo credits reveal that there was a huge reliance on Project Vireo for this project, and that of course means that the project relied upon and show-cased the best photographers in America, both present and past. It was really fun to find some “old friends” from my formative years. That 12-year-old kid with the Peterson Guide was also looking at amazing National Geographic photos by Frederick Kent Truslow at the time, and I was pleasantly amused to find Truslow photos in the book, among other classics. Some photos are timeless.

In summary, I do think the questions I posed at the outset have been answered for this book: the Knopf/Audubon guide does an excellent job as a complete reference guide to North American birds, and a bit of a lesser job as a complete ID guide. This is in no way the fault of this book—you just can’t have it both ways. Ah, back to the field guide app on your phone! I would recommend this book in addition to Sibley, but not instead of Sibley.

This praise-worthy and monumental effort, one that maybe could only have been done by committee, suffers solely from a lack of robust identity. But again, if one considers it as a cross-over hit, a hybrid guide, it will well satisfy. I maybe still haven’t answered my own question as to what the perfect field guide could or should be in the 21st century. But as I often do, I may start reading them all again, even if not in the actual field, starting with that early dog-eared Peterson. When re-reading them, I still learn something new each and every time. This will be easy and satisfying with the new NAS/Knopf Guide. Such is the reward of books, and especially this one.

And where the Birds of North America bills itself as a complete guide to birding, leading to some of the questions outlined above, the Trees of North America is more direct and specific in its claim: the complete identification reference to trees. That helps, although one quickly realizes that at 591 pages and 7 ½ inches by 9 ½ inches, it is really too large and heavy to be a field guide. Seat back of the car maybe. And a weighty and complete reference it is. 540 species are covered, with over 500 range maps, and it is well illustrated with 2,500 color photographs. Ecology, identification, leaf shape, and so much more are covered and covered well. As in the NAS Birds of North America, topical essays are offered; these short and readable essays by knowledgeable botanists offer great learning and insight into a variety of fascinating subjects.

For someone who is primarily a bird person or zoologist in general, this tree book takes more work than the bird guide. But the color keys and an excellent glossary facilitate easy use. This is a more scholarly, indeed more scientific, effort than the bird guide, taking more focus and invested effort to use and learn. And I think that is a good thing.

Although advertised as a complete guide, it is not quite that, but the book doesn’t really tell you that. Not all tree species in North America are covered. 540 species are covered here, but the Sibley Guide to Trees covers over 600. This may frustrate the user at times; for example, I looked up a local favorite, the Dwarf Hackberry, but it was not covered. The NAS guide covers 2 species of Hackberries, where Sibley covers 13. Admittedly, there are some recent taxonomic changes in the hackberries, with lumping and splitting (as prevalent in botany as in ornithology) and different schools and interpretations, but nowhere does the NAS Guide to Trees readily explain how the choices, of what to leave in and what to leave out, were made.

While the photography is excellent, in some regard trees do not lend themselves as well as birds to a photography guide approach. I love the shots of whole trees, leaves, bark, flowers, catkins, and fruit. All are helpful and educate well. There can sometimes be difficulty in making a quick ID though due to the very nature of photographs—varying lighting, shadows, settings, habitat, and lack of scale. With photos, it is often hard to make side-by-side comparisons of tree species. This is a generic issue here, not one with this book. NAS Trees of North America does it as well or better than any I have ever seen.

Unlike most tree guides that use either herbarium pressings or drawings of leaves, the photo approach makes it more difficult. Not impossible; I’m only saying you have to work harder at it, integrating text and photos, more so than you need to with guides that use drawings. This is not a bad thing, as this is how true learning occurs rather than making a quick match, moving on, and forgetting it next time you see a given tree species. But one frustrating aspect of the NAS guide is that some species don’t have photos of the leaves. The flip side is that photos show the foliage and vegetative structure better than drawings or paintings, however good. Trees have depth and complexity of structure that are highlighted very well by photos.

This work is impressive, scholarly, and I see the new NAS/Knopf Trees of North America sitting alongside the “old” Knopf Sibley Guide to Trees, whether on the back seat or bookshelf, as an inseparable set to be used with each other again and again. As I mentioned with regard to Birds of North America, I own and cherish all the bird guides, and I guess am now tending in that direction with tree guides too. Gosh, I love books. You can never have too many.

Editors' Note

The titles of these books use the contemporarily common but inaccurate convention whereby "North America" refers only to the continental U. S. and Canada. We hope publishers and authors will replace this standard with more geographically accurate and less exclusionary language in the future. For more on this topic, click here.

–Frank Izaguirre, Book & Media Reviews Editor

–Michael Retter, Birding Specials Editor

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Clay Sutton is a co-author, with Pete Dunne and David Sibley, of the classic Hawks in Flight (Houghton Mifflin Harcourt, 1988: second edition, 2012). Clay and his wife Pat Sutton co-authored Birds and Birding at Cape May (Stackpole Books, 2006), among other titles. Clay was a long-time instructor for the ABA's Institute for Field Ornithology.