bird id help

I set out a decorative birdhouse in my garden and much to my surprise a bird moved in and built a nest.
The bird is about the size of a Chickadee but more slender, it has a longish very slender beak.
It is a plain grey/brown with no eye streaks or barring, its chest is lighter than its back.

I know this is not much of a description but I am hopeing someone will recognize this little friend.
About a month ago I noticed a bird singing I didn't recognize, then I saw a bird had occupied the house.
I started watching the bird and sure enough he or she was the new singer in the neighborhood.

I am not sure if it really is off its usual route or if I just noticed its song because it was so close.
It is quite shy so have only caught gimpses and no chance for a picture yet.

Sure hope someone has an idea.

A house wren is a good bet.

That's what I was thinking. They will try to build a nest ANYWHERE! Back when I used to hang my clothes outside, I kept finding a buch of little sticks inside a leg of my jeans. Again and again. I decided to keep an eye out to see who was doing that...I was amazed at watching this cute little bird put stick after stick down in the leg.

The male wren will build several nests in many different locations, in hopes of attracting a female to one of them. She has the final say on where she raises her young.

Yes! that's it. Thanks it has such a pretty song. I guess it has been in the area and I just never saw it.