Could you just block up the area that they like to build in?
I had a friend that had a wall AC that he found birds in. He couldn’t bring himself to kill them…and turning on the AC most likely would…so he lived with sweltering heat until they were gone.
He then used Duct tape and WIRE to completely seal off the AC.
Next year, somehow, they got in and layed eggs. It must have taken them forever. He sighed, lived with the sweltering heat and let the chicks live.
The next year…he went all out. I can’t remember what he did but it was an A++++ effort. They still got in and layed eggs.
He gave up and bought another AC for another window. 
So, the only solution is to nuke them from orbit, eh? Gotcha. 
It’s the only way to be sure!
Might I suggest a sign of some kind to provide backup protection? “Out of order – use alternate mailbox – do not disturb” might be just the ticket without drawing too much unwanted attention.
See post #17.
Bumping for birdie update! What’s the story, MissGypsy? Got little wrens yet?
Nothing yet, still just little eggs. Mama Bird just sits there and peers at me when I open my front door, rather than flying away. I like to think she’s guarding them as they get close to hatching, or that she’s a friendly little thing who likes me.
Just chiming in to confirm from our experience with our balcony pigeons, that is a myth, and human scent won’t bother the birds. We were worried about that at first too, until we learned otherwise.
But I have heard from people on pigeon boards who have moved a nest, and the parents could not find it or possibly did not realize it was theirs despite it being close by.