Hi

Same has happened to mine but I do have a sparrow hawk about so something has happened to one of them .

i would guess at a visit from a sparrowhawk sorry!

Apart from the sp.hawk they also prefer to have covering foliage around their home, so the nest box would be better on the fence behind the shrub, tho' not so good for your viewing of course.

I don't know if wrens use nestboxes, but the male wren builds several nests ant the female chooses the one she likes best....

I thought that Stera! We have had several Wren's nests which were never used. Makes you feel sorry for the male Wren, all that work and then some snooty female doesn't like the lay-out!

Having said that, just because you have no cats doesn't mean you don't get a visitor, we do from a stray cat, can't keep it out! The Blackbird let's us know when it's about. The top of the fence looks ideal for a cat to sit and wait, might not get it, but would put it off.

Thanks everyone..i thought i was doing something wrong.
Yes the Male Wren does all the work but that's life ..ha ha Lol