Hey Roger, The others have some good ideas. I think I will represent the other side of the coin though.. iBird Pro: tons of calls/songs and descriptions. BirdLog North America: To make checklists to submit straight to ebird. Easier than pen/paper. BirdsEye: Locate a specific bird, see bar charts, and see rare bird alerts. Oregon2020: View the Hotspot squares for helping with the Oregon 2020 project. Master Birder by Larkwire: Bird sounds quiz/game. Rode Rec: Good recording app - for recording unknown calls and then puzzling over them later. Not totally related, but Motion-X GPS: You can pre-download terrain maps for areas you wont' have cell service, the gps still works when out of cell range, giving you a second version of whatever is your primary map. (it does use up your battery a lot though). I had other ones similar to iBird Pro (Peterson Birds Field Guide), but I didn't use it much, and didn't have enough space on my phone for all of them. Cheers, Brandon Wagner