Well, this brings back old unpleasant memories. Not my C/F but another car I had parked outside my home near a wooded area behind my house. To make this short, this went on for months. Repairing and trying everthing to keep them from coming back. I trapped 25 of them, took them 10 miles away and turned them loose. Still more backups came in. I finally hit on a thought, What would deter them most? I took a old sock filled it with foam rubber tied it under the hood and poured "FOX URINE" over it, Yeah you read correctly, fox urine.
That is one character they don't want to mess with. Never had a problem since. You can buy "FOX URINE" at ****'s sporting goods or Walmart sporting goods. Don't laugh it works. I had to do something.