Jim the Bird Watcher?

My barn swallows are back. I have a couple of new bird nests again this spring. Last fall I cleared out from above my patio on the underside of the second floor deck, all the nests from the last 2 years. Two summers ago I had barn swallows and if I remember correctly, last summer some sparrows used the same nest but added to it. They might've just finished another one that the barn swallows started but didn't finish...I'm not sure which it was. The spaces where birds always build these nests is over my patio on the underside of the deck above. There are several slots which offer a good place to build.
I think the birds get confused when they are building them because each slot has a little bit of nest in it. Eventually they manage to finish a complete nest and live in one of them. I'm not sure exactly who built what and when but out of 6 slots 5 have at least part of a nest built into them. Two of these nests look fairly complete. I haven't paid very close attention lately but I figured the new nests were built by sparrows again. Earlier today I think I saw the barn swallows again. I couldn't be sure because the glass on my patio doors was dirty. Whatever they were they were not sparrows. I cleaned the glass now and I plan to keep an eye on them to see what they are.

This is a barn swallow.