I saw Tree Swallows going into bird houses both small and large at Nisqually National Wildlife Refuge.   There were also tree swallows that made nests in the eaves and other openings on the Twin Barns.  The babies were sticking their heads out of the opening with their mouths wide open when they saw their parent approaching.  Sometimes they would be fed, but sometimes they would be teased by the parent…. I think they were trying to get them to leave the nest!