What am I doing wrong?

Hi What am I doing wrong, if anything? Here has been my problem from day one. Started off by doing a hardwire to my existing doorbell only to find out the sound from the doorbell chime inside my house wouldn't notify me when someone was there Took it off hardwire. Now I am using it in my backyard as a battery only camera. Have it on a table right now. I have it set for 30 feet and took people only mode off and have it on the frequency setting. It will pick up a squirrel if it runs across my patio but it won't pick up any small birds that are right in from of the camera and within the parameters of the mode settings. If I have this set to include my backyard fence, shouldn't it pick up squirrels or birds that are on the back fence? Just curious. Thanks in advance.