oaw[25] - bird's nest

That is, I think, a wren's nest ...
The male builds several nests, and sings [loudly] to advertise to potential mates. She chooses a nest and matters proceed in the usual way ...
[I don't think this one has been used, but I will get a very careful look at the end of the nesting season - note that wrens sometimes roost communally in old nests]