As a city dweller, I might have wondered about the statistic on the number of birders in the United States cited below. But having worked side-by-side with a dedicated birder at School Library Journal (who has traveled far and wide in pursuit of the hobby) and witnessed how a perennial second-grade unit on these creatures brought those students (and their parents and siblings) back year after year looking for new titles on our winged friends, I have no doubt that the number is accurate. Here are a couple of the latest digital guides to share with the birders—armchair or otherwise—that come into your library. Bird-watching is one of the fastest growing outdoor hobbies in the United States with well over 51.3 million Americans reporting that they participate. The activity has generated enthusiasm across all age groups and demographics. Many of us grew up with a tattered copy of one of the “Peterson Guides” in our home. Today, with family members pinching and swiping their way through books, it's no surprise that digital references for these hobbyists are a growing category. Indeed, there are a host of great apps to assist those who want to sharpen their observational skills. Quality resources include iBird in all its iterations, from the Ultimate (pricey) to the Lite (free) versions, both available for i0S and Android, as well as National Geographic Birds: Field Guide to North America (also available in a free, Birds Lite edition). And, of course, there’s Peterson's Birds Pocket Edition: A Field Guide to Birds of North America. Is there room for additional competitors and improvements? Enter the species-specific app. Since warblers are one of the most confusing and difficult to identify of birds, it makes sense to offer a guide on them, and Princeton University Press and One Hundred Robots have obliged with The Warbler Guide (iOS $12.99; Gr 9 Up). The app is based on the award-winning reference of the same title by Tom Stephenson and Scott Whittle (PUP, 2013). Brief descriptions of the creatures are offered, along with icons indicating typical behaviors and preferred habitats. Particularly noteworthy are the multiple views of the birds that allow users to see the creatures from many angles including below with pinch-zoom properties. Other welcome features are the exhaustive song and vocalization library for each warbler, and the array of images depicting differences for age, plumage, season, and activity. The app can be customized by view, season, location, and order. There's even an opportunity to paint the bird bodies, which will aid in identification when in the field, filtering out some of the many possibilities. A user guide is provided. Highly sophisticated both in navigation and content, the app is designed for experienced, dedicated birder. Combining the depth of the print guide and the technology of digital, Warbler will make a good companion for those hoping to identify those beautiful but difficult-to-identify warblers on a walk or hike, or during window bird-watching session. Student researchers looking for images may also find it useful.—Elisabeth LeBris, Director Library Tech Center, Kenilworth SD 38, Kenilworth, IL Similar in design and depth to the National Geographic Birds: Field Guide to North America, the Collins Bird Guide (Touch Press/Bonnier Fakta/William Collins, iOS $17.99; Gr 5 Up) focuses solely on the birds of Europe, North Africa, and the Middle East. The app is based on the book by Lars Svensson and illustrated by Killian Mullarney and Dan Zetterstrom (Collins, 2008). Species can be searched by name and a variety of attributes including plumage, habitat, and size. Each animal is drawn in various poses with labels describing its physical features. The text is limited to short descriptions of the creatures’ appearance, and typical flight and characteristic voice patterns. For each, a small distribution map is provided; a bird atlas is available as an in-app purchase. Enhancements include an audio of each bird’s call and a selection of videos (13 in all) of the some of the animals in their natural habitats. The videos are superb, both informative and appealing, and set this app apart from other guides. (Additional videos are available as three in-app purchases, totaling 794 video clips.) The app’s other noteworthy features include a comparison guide—helpful in the field for identification purposes—and a “share” button that alerts other birders to a special sighting. There’s also an option to create a “life list” of sightings. Both navigation and image size changes are easy. Because of the range of the birds featured, the app may not be essential for North American birders, but for those wishing to see and hear some nonnative species up close, this will be a worthwhile purchase.—Elizabeth Kahn, Patrick F. Taylor Science & Technology Academy, Avondale, LA For additional app reviews, visit our dedicated webpage.