Enough! San Jose woman wants bird to stop tapping at her door
Maybe he thinks he's a raven, or perhaps, by adding food into the fray, you have given him something to protect even after the reflective challenger disappeared.
Why does Walnut Creek cat yowl mornings and nights?
If you haven't already, take him in for a check up to make sure there isn't a medical reason for the howls. If he gets a good report, time to consider other factors.