Secret Lives of Wild Animals Captured by 1 Million Camera-Trap Images
wired.com
wired.com
That said, some of the animals in the pictures saw the camera -- not exactly discreet.
I 'hacked' together a FOSCAM IP camera to capture wildlife in my backyard. Was about $70 for the camera. There's a newer IP cam out from them that costs about $150 and has a much higher resolution.
Getting power to the cam was easy as I ran a really long power cord. It is cheaper to run Power Over Ethernet if you have longer distances (just buy an injector and splitter). If I move the cam further into the woods, I will do PoE (although bought the equipment).
If I go any further into the woods, I will use a solar panel, battery, and inverter.
FOSCAM has motion detection software on-board, so it would also work great at bird feeders around your house.
We, (local crime watch), use the same types of cameras to keep an eye on vacant houses in the neighborhood. So far we've assisted the police in tracking vandals and drug dealers. (Not to mention countless non-criminal animals...)