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.