In the 60s I took a course in animal behavior at UNH. I found nest building to be fascinating. Each species has their own specific design, and they build without blueprints or having watched their parents do it! And with no hands!
As the name implies, these guys are quite prolific here in the "Old North State"! Quite friendly, busy nest builders, and very noisy... They build 3 or 4 nests before deciding which one will get their eggs. Our neighbor's cat comes by to check out all the obvious places every other day -- raises quite a ruckus!