One of the tools I've been using in my backyard wildlife identification efforts is the Merlin Bird ID app (I'm using the Android version). This app is aptly named, because the ID capabilities are like some sort of dark magic!
There are a fair number of useful features in this app, none more so than the photograph identification tool. You simply upload a photo of the bird you want to identify, select the date and location where you spotted the bird, and the app gives you a list of possible birds. Each entry has information on the bird itself, and a number of excellent photos to compare your candidate against. In most of the trial cases I've given the app, only two or three candidates are usually returned, a testament to just how smart the "brains" of this thing are (all of its recommendations for my photos have been spot on so far).
Another feature that I haven't used much yet is the bird-call feature. While examining details on a bird, you can listen to a number of its calls, which makes identification by ear a lot easier. I cannot recommend this app highly enough!