... Location

It seems that Organ Pipe Mud Dauber Wasps found the inside of the garage to their liking.

(You were expecting wrens?)

I was initially alerted to their presence by the loud buzzing sound they make, click here to hear.

Above we see a partially completed 'organ pipe'.

And shown here are two wasps busily making nests.

The female wasps will find a mud source and roll a ball of mud, as big as they can carry, grasp it with their forelegs, and fly it to the nest site.

At the site she will mix it with her saliva and add it to the growing pipe. If you bigafy the above image you can see the mud ball next to her head, which she uses to push the fresh mud into place.

The darker brown area is the recently applied wet mud.

Once complete the wasp will find and capture several spiders, paralyze them, and stuff them into the pipe.  She'll them mate at the nest site, lay an egg in the pipe and seal off the chamber. Her mate will guard the pipe as she goes off to find more spiders (males aren't completely useless). There can be up to seven chambers in a pipe. Once the eggs hatch the larva will feed on the paralyzed spiders and when ready the wasps will chew their way out of the pipe.

Of course, there will be no spiders or eggs in these pipes as once the door was closed construction ceased. I know not where they may have relocated.

Quite a few false starts, perhaps each time we left the door open as we worked in the yard?