"They started building it in the elbow of my eavestroughing. I noticed there were no eggs in it, so I took it down as it was in the highest traffic area of my deck. Side entrance, BBQ, dog play area, etc.
They then started building in a maple tree…"
There are about a half-dozen nesting records for NB that I'm aware of and undoubtedly many more that have never been discovered. It's a very hard nest to find. As you've likely read, they don't build a stick nest; they lay their two eggs in large cavities such as caves or hollows in rock piles, in large hollow logs, etc. Most NB nests reported have been in piles of large boulders at the base of rock faces, usually with a east, south-east or southern exposure.