Ok, so it'd definitely not birds. I have moss growing in a tray with another tray wired upside down on top to protect it. The holes are too small for a bird and yet last night something got into it (the moss on the benches wasn't toughed thogh). Decided to go the whole hog and camo up (thanks for the idea Damien). So on with the camo and balaclava (it's here at night) and I'm out hiding out in the bushes ready to catch the culprit. So after the next door neighbour calls the cops on me for loitering......only kidding. I'm already....I said I was ready.....oh come on already, it's cold out here, just show ya face so I can go inside. Well it showed it's face alright, on the rail just above my head
is a possum, is it cat is a..... of crap it's a rat
Yes that's right, a rat. I didn't get a real good look as it startled (read "scared the crap out of") me and then made a hasty retreat. Upon further investigation I found a hole in under the pile of trees I cut down to be mulched. It appears to be a native bush rat of some kind as it was different from a normal rat. I suspect it is looking for grubs or roots to eat
O bugger, did I say native........I can't kill it now, can I
I will hope it just moves on then
.
At least I know now and can plan some defence.
Josh
We do have a neighbours cat that comes over when we aren't here (which may go missing soon) but not sure if it is the culprit. I had an issue with a possum eating new shoots but don't know if it would dig holes. The holes are too deep/narrow for a bird I think. Might have to set some deterrents I think. 
Different in the way the hole is dug and none of the trees with moss are touched which is where they go normally and only at night, not during the day at all. My mother (trust mum) thought bandicoots but don't think they'd get up in the benches. I'm very curious as to what is. I know the neighbours cat is pushing its luck 
I will investigate further. 
, you'd know too as you'd find a few extra pebbles buried away 
