Birds in my tunnel

Every morning when I go in my tunnel there's a robin and a wren in there. Actually, the robin seems to hang out in there a lot all day. He doesn't even bother flying out unless I go right up to him.

I'm actually quite happy to have a robin in there, because they are pretty good at eating caterpillars and pests, but I'm beginning to wonder if it's a bird that's nibbling on my aubergines. I haven't got a very good crop of them, just a few fruit growing to a decent size. But the biggest one, my pride and joy, now has half a dozen circular nibbles on it, which look very much like what the bluetits do to my cooking pears outside.  It's really not at all like slug damage, just perfect circles, and I don't know anything else but a bird that would do that.

I didn't think robins ever went after fruit so I doubt he's the culprit, but I'm not too sure about wrens. And of course it's very possible the bluetits are going in there when I'm not around. Anyone know if wrens would do it?Or anything else that might do similar damage?

Mystery solved. I put a box trap in there overnight and this morning found a mouse in there. That's a first, never had them go after aubergines before.

Robins do not need much of a gap to get in and out, we have a robin (probably raised in a nest in the shed) that uses the lawn mower handle to roost on at night in hard weather.
He gets in under the 2"corrugations on the roof sheeting.

I am sure you could sort out a robin 'porthole' before the weather gets too cold .