I have a House Wren nest on my deck. The house was supposed to be decorative, but this is the second year the wrens have used it to raise babies. From what I've seen, the main dish offered are spiders!!! Occasionally small butterflies also.
The house Wrens use sticks for their nest material...and they will put those sticks into every nest box they can. I have to keep emptying those sticks from the BB houses.Excellent! I watched a female packing in nesting material to a nesting box. A busy as I've seen a bird, a trip every 30 seconds or so. Too far for pictures without spooking her.