I’d been hearing House Wrens since April 20, but hadn’t seen one. On April 28, I heard one singing from the area behind the Sailboat where a bluebird nest box has been installed. This box was inspected on April 10 and although bluebirds had constructed a nest inside, it didn’t contain eggs.
I hadn’t seen any activity around the nest for several weeks and had written it off. A House Wren is now putting the box to use.

Male House Wrens arrive on the breeding grounds first. They may construct several nests, but it’s the female that chooses which one to use for raising young. So, although there is certainly some nest building going on in the box, we’ll have to wait till the females arrive to see if this particular nest will be used, I’m betting it will!
That’s it! They have a very cheerful opinionated sound to their song.
What is the reddish-headed bird that perches on the highest peak of a roof and sings a very complicated song? I have a few around my apartment building.
A House Finch is the most likely candidate.
http://www.allaboutbirds.org/guide/House_Finch/sounds