Simple. Load your save file, press pause, go to Stats and then Vehicles and scroll down slowly until you see two options: Stunt jumps found
& Stunt jumps completed
. First option tells you how many jumps you've found but not necessary completed, and the second one tells you the completed jumps.
Also, I read about your problem with the last Pigeon. I've got a way faster option for you. It's called Simply Native Trainer
- downloadable here
(version 6.4). It'll teleport you to the pigeon you haven't shot yet. Please tell me if you wish to go deeper with this option, and if you'd like to use it, please tell me the game version. Hope this helps.