GardePro No-Glow Trail Camera
For catching someone on your property without the camera being spotted, you want a no-glow IR camera so there are no visible red lights at night. The GardePro No Glow is great for this, completely invisible IR, runs on batteries with SD card storage. If you want motion alerts, the Tactacam Reveal Pro is tiny and cellular (needs a data plan). Mount it high and camouflaged, and consider two cameras on different angles so you've got backup if one gets spotted.