Scratchinn sounds like rats or chipmunks, wire eaters for sure. Get rid of them!
Every Spring here I get robins under my skoolie hood building nests. last Spring they built 4 and I removed 3 of them. The last time there was 2 eggs so I let them be, and they return every year. Tough little birds because the bus is wide open to some pretty vicious winds all winter and spring.
If you have rats get a pesticide specialist, they have the right stuff for those guys. I had them in my Suburban engine compartment finding warmth I guess.