What kind of Animal would do this?

Holy **** that is a lot of junk.
A real nest.

That could be a wren nest.

I think I had a mechanic do that... once ;)

Never seen that but have had dirt dabbers lock up the A/C motor. At first I thought it had seized but with a wrench going back and forth I was able to crush the nest(s) and it has not happened for the past 9 years.

Must have been a large hole in the A/C housing to bring all of that through especially for a bird.

I don't have a picture, but I noticed a big nest a few weeks back on top of my left slide. I have awnings over the slides and this nest was big with large pieces of sticks, etc. much larger than a bird. It was a squirrel nest. Solution: Tools required
Step ladder
Stihl gas powered blower

Procedure:
Set ladder at rear of slide
Start blower and let it warm up
Climb ladder and aim blower into area under the slide awning
Full power on the gas engine

The Fun:
Watching the nest and the squirrel blow out the other end and the squirrel running like crazy for the nearest tree after a 11' drop to the ground.

Preventive:
Stihl chain saw and removed the entrance and exit ramp limb(s) from the nearest tree to the rear of my rig.

Problem solved.

Pack rats. They will pick up and carry just about anything they can into their nest. They're very strong and determined little buggers. Never underestimate them.

Pack Rat, Squirrel/Chipmunk, birds

Eliminate the threat immediately. I had a squirrel family take up residence under my engine cover several years ago. The little f*****s chewed away all my vacuum lines,many wires, injector casings and throttle linkage of which Had to fabricate myself since ford stopped making the parts years ago.
Use critter ridder, shotgun shells, dynamite, whatever it takes.