Saturday, July 8, 2017

Review: A Swift Guide to Butterflies of North America

Earlier this year I decided to step up my butterfly game, honing my ID skills and seeking out new species more deliberately. For the most part, I’d call myself a casual enthusiast, in that, for as long we we’ve been birding, I’ve been keen to get photos of butterflies as well, but as a secondary activity – something to focus on when the birds are quiet. And even when I managed a decent photo, I hadn’t always doggedly worked out difficult IDs or learned what diagnostic features I should key in on next time. 

We own a copy of the Kaufman Field Guide to Butterflies of North America, which is a great resource on its own, but just as we own multiple bird field guides, it’s worth exploring how other authors and publishers choose to present similar information. Fortunately, Princeton University Press has a brand new edition of A Swift Guide to Butterflies of North America, by Jeffrey Glassberg, President of the North American Birding Association (NABA). The first edition of this guide was only published in 2012, so it’s surprising that a second edition should follow so soon after. Not being familiar with the earlier edition, I obviously can’t address what updates have been made, but I do have plenty of thoughts how well it meets my expectations as a reference.

Firstly, this is a photo-based field guide, and the photos are stunning. Each species entry has a large primary image, with supporting images surrounding it. Notably, the butterflies haven’t been isolated by cropping out non-essential details, but are left in the context of their immediate environment. Field guides often remove these to help make more direct comparisons between species, but Swift Guide selected images, and oriented them, in such a way that similar species are usually shown in comparable poses. Species entries typically take about a half-page, but sometimes run multiple pages, meaning that a lot of variation is shown, and in nearly every case the photos are larger than those shown in Kaufman, allowing you to see more detail.

But a field guide is more than just images. As for the supporting information in Swift Guide… well, there’s a lot to unpack. Before checking out the book’s introductory text, I flipped through the species accounts to get a first impression, and really didn’t know what to make of it. In order to conserve space and keep the text as close to the images as possible, the layout ends up hiding some details in plain sight. To illustrate, here’s the sample entry for Hawaiian Blue. Without scrolling ahead, try and determine on your own how large this butterfly is. 

Now look directly above the name, Hawaiian Blue, and you’ll see a short white line. That line represents the size of the butterfly’s forewing, from its base to the apex. Not only is this not intuitive, it’s difficult to use in practice. But in the field you’re going to see an entire individual, comprised of more than one dimension. Contrast this with Kaufman, which shows you the life-size silhouette of one species per page, and keeps all species on that page in proportion to one another. This gives me a much clearer picture of what to expect when I actually see a butterfly. A line is too abstract, too far removed from the actual, living butterfly, and for species that commonly hold their wings out to the sides, doesn’t convey how large it will appear to you when you encounter it.

I wanted to put this field guide to the test so I looked back at some photos of butterflies I haven't been able to ID yet, including difficult groups such greater fritillaries, and buckwheat blues. To be clear, it may not even be possible to ID some of these species without examining them in hand, so it's not a reflection on the field guide where I haven't been successful, but I was able to narrow down my options based on the information provided, including features that aren’t discussed in the Kaufman guide.

For the Dotted Blue complex, Swift Guide very helpfully provides a separate range map for each subtype, allowing you to see which varieties appear in different regions. Throughout the field guide, I was able to find lots of other examples where subtypes received their own entries (and with their own range maps), too.

While, on the whole, it’s super helpful to have separate entries for different subtypes, it does create some confusion where the book’s organization is concerned. For instance, there’s an entry for Aphrodite Fritillary on p. 165. At first glance you wouldn’t know that there are other entries for the same species: the page before and the page after are both for Great Spangled Fritillary! If you live in the west you’ll have to flip ahead to p. 171 to see what “your” Aphrodite looks like.

Although this book is difficult to navigate at times, it’s an absolutely lovely field guide. If you’re looking for a photo-based reference, with lots of large, high-resolution photos, Swift Guide is for you. This is a wonderful addition to our library, and has already proved a handy resource.

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