How to get birds to stop nesting and coming back?

Block this area off with mesh netting or something else..if this has been a continual problem..you should have taken care of this BEFORE the breeding season. You can legally knock the nests down if NO eggs are in it. Once eggs are laid you are stuck with the nest as all native wild birds, their eggs, nests, and parts are protected by the Migratory Bird Treaty Act. At this point the birds are just wasting a lot of time and energy which may affect their potential to have a successful nest somewhere other than your porch. Block it off once and for all.