Whether you’re hiking in the mountains or strolling through Cherry Creek Park, it’s always nice to have a field guide handy to identify wildlife. Each spring, the Rocky Mountains funnel migrating birds right by Denver, and a field guide can help you identify those chirping chickadees and dusky warblers. But what if you’re aiming for a light pack, or just want to keep your hands free of cumbersome books? Check out these nature apps that put field guides in your pocket with no extra weight:

Audubon Field Guides: The National Audubon Society’s multiple apps allow beginners to browse by bird shape, while expert naturalists can geek out on the detailed descriptions and range maps of each species. Keep the bird app handy to identify spring migrants. $4.99-$9.99.

MyNature Animal Tracks: Sometimes the only wildlife you see on a hike are a few paw prints ambling across your trail. This handy app will help you identify unseen critters by the scat and tracks they leave behind. The app includes fore and hind limb tracks, gait patterns, detailed scat illustrations, and range maps for each species. $6.99.

Geograph CO: Ever wonder what kind of rock is underfoot along the trail? Geograph CO uses U.S. Geological Survey data to tell you more about the land around you. Interchangeable layers allow you to identify geological formations, elevation, past earthquakes, mines, oil wells, rivers, and even fire history. Even better, this app doesn’t need a cellular or wireless connection to work, which allows you to access your inner rockhound when you’re deep in the woods. $4.99.

LeafSnap: This app makes tree identification a snap. Take a photo of any leaf and LeafSnap will use visual recognition software to identify the species. LeafSnap is best suited to backyard adventures, as a Wi-Fi connection and white photo background speed up identification. Free.