I bought a couple of DLink cameras at Best Buy for about $50 each. There is no monthly fee, and you can set the cameras to record all the time, or just when motion is detected. You can vary the sensitivity of the motion, but for outdoors, you might just need to turn them on and record every night. They also can "see" in infrared, for nighttime.
You log into their website to do all the managing, and you must have WiFi and a good signal at the location you want to place the cameras. I got the "indoor" cameras, but they make indoor/outdoor ones also. They have worked out really well.
I have caught a variety of hanky-panky with my birds in the greenhouse (who prefers the taste of which tree, etc), and also discovered where the mice get in. I wish I could figure out how to speed up the playback, and I would use it for time-lapse cactus flower blooming!
Carolyn