Well, they are nasty.
They NEVER appear when I am near, but every morning since the weather became warmer, every single piece of moss is either gone, or in the ground.
If the moss is dead (sphagnum moss, covering the surface of the soil to keep humidity), they take it away to make nests (it's almost Springtime here).
If the moss is alive (and sooooo difficult to make it stay alive around here...), they simply scratch it away to look for worms underneath.
Short of being a bird killer (which I dislike), what can be done?
Live with holes on the soil and no humidity layer whatsoever, forever?
Any ideas?

Hi Clicio, I had the same problem with blackbirds messing up with soil on my bonsai pots (and with the little moss I have).

I managed to solve the problem just putting in front of the bonsai tables an ugly monkey puppet which belonged to my son... acting as a scarecrow, they never visited my balcony again!!

i know anything that reflects with light works. Doesn't look pretty but some people hang old CD's and with the sun reflecting off of it the birds wont go near it.
or something like this i believe its called a flock reflector.

Good ideas here.

Another, get some metal screen and cover the moss/dirt with it. Cut a shape to fit the pot and a hole in the middle. I got a pretty large piece of screen made of wire about a millimeter and square holes about a centimeter. Problem solved. Water goes right through. Birds and squirrels don't.

I had a large square pot with seedlings in it and a large square piece covering it, which later became the first coarse sieve when mixing up potting medium. Multi purpose.

Get a cat or two. I have 5 and we don't see any birds around in a wide radius. But they like to play with fertilizer pellets and dig into the soil oh wait......