we have found that simple chicken wire fence 2-3 ft tall is usually all it takes to keep our birds from roaming to the neighbors horse pasture, but our are larger birds who don't fly much unless being chased. It won't keep anything else out, but works for a simple deterrent.
B:
To add to Fisher's suggestion, I've found that birds will always come to a food/water bowl (maybe placed next to your back door)....then they'll eat an lounge a bit...when they get around to scratching they are near home base and have a lot longer walk to get off your property....my two cents...