Try spraying vinegar around the area.
Just pour it out of the jug, or use a sprayer or spray bottle.
This works well for cats, dogs and skunks (the furry 4 legged kind)
Another thing that works especially well for cats and skunks is putting
3-5 mothballs in an old sock and tie it shut, and put along the fenceline,
or wherever the critters are getting in.
I am pretty sure it will work well for anything including birds...
Humane and effective...