Arghhh! Bird in the greenhouse!

For the third time this week a stupid bird got stuck in the greenhouse. I've got a bit of a bumper basil crop going on in there at the moment so the last thing I want is it covered in sparrow poo.
The bird is coming in through the autovent then failing to find its way out.
On Sunday Him Indoors sorted it out. On Monday I sent the dog in to chase it out, since I really don't do birds. I hoped that in his usual hyper terrier way he would create a commotion and get it moving, since at that point the bird had actually got itself wedged between some garlic that is propped up to dry in there, and the window. Unfortunately, the dozy hound just stood transfixed in the doorway, staring at it.
Today the in-laws discovered it first and chased it out. If they hadn't been there it could have been stuck all afternoon. Don't fancy our chances of making pesto with the after-effects of 4 hours of panicking sparrow, do you?