That would be so exciting to see a nest! Your zoom lens did an excellent job capturing the 'tiny knot' Thanks for posting. Ruth

You should put it out as soon as you see the females. From my observations, they mate within a day or two of their arrival and begin making their nest the next day.

We get carpenter bees as well. Loads of them. But I never saw them going after the hummers. I have my feeders under my back patio and the carpenter bees are usually in that same area. Hummers can be pretty aggressive so I wouldn't worry about it. When I spot the carpenters nest I spray right into the holes and then immediately plug it up. Also, keeping regular bird feeders full attracts other birds that like to feed on the carpenter bees. They don't get all of them but I've seen quite a few dead on my walk way. They also kill their mate once they've mated so that could be why I see the dead ones on the walk.

Thanks Paul, Their nests are so cool, and VERY hard to see! I found 2 in the Fall one year, but this is the first time I've ever seen one in use. I probably would have gone all summer without seeing it, except that I was walking under a pine tree branch and suddenly heard a hummer take off. That make me look really closely.....and there it was! Even now when I look for it, I have to look for awhile. They're so cool!