Hard to really tell from an aerial photo without a few more details. How's the water situation? Is it good bedding cover? Are you seeing any sign of old rubs on outer trees bordering the fields? 40 acres isn't going to hold a lot of deer no matter how good the total situation but it looks like you may have a little something there to work with. Good outlaying nearby food source and from what little I can see from the photo, may have good bedding cover which is very important. Really home in on the edges of that wooded lot and look for trails. Also locate a water source and look around the banks for tracks as well.