Little Carolina wrens--will nest anywhere. I had hung the nest bag on a plant hanger for a squirrel that I had evicted from the release cage (six months after I released him. He'd play in the woods by day and sleep at home at night). But I needed the cage for the next litter that had come along. I don't think he ever slept in it, but some wrens thought it would be a good spot for a nest. You can also see in the background where they did actually use a bird house--by building a nest on top of it!
Today I saw that the wren was carrying a bug rather than nesting material--so I sneaked a peek. These guys are only a few days old. With Mom bringing bugs about every 15 minutes from dawn to dusk, they'll be ready to fledge in a couple of weeks.