Bird Watching: Bluebird house mystery, 1 by gessieviolet

gessieviolet wrote:
It is gorgeous here after some very unusual weather. I am checking things out. Have heard bluebirds in trees and once saw a pair inspecting my new bluebird condo! Have a family nest in this same spot for 4 years, my handmade birdshack was about done with so I invested in a cedar beauty.

Been anxiously awaiting arrival of my regular yearly residents. On a whim I opened the front of my new house; look what I found. This does not resemble any bluebird nest I have ever seen. Any ideas?

I want my bluebirds but I don't want to destroy this, either, if it belongs to another species.