I have a layer of dead mice on mine which seem to do the job nicely.
Mice?...pigeons are better... + ensure there's one in your cold water tank, so it decomposes nicely for when you need a survey.

Give over how could you possibly lifthimthe loft hatch up?

Funny you should say that.... NT!!!
I was going to suggest nailing a sleeping cat to the loft hatch ............you might find a quite large one in the Tea thread if your quiet![]()