would it be easier to cover the pool then keep them locked up? I have heard of people using childrens balls like the big rubber beach balls, floating in the water with a tarp over them to keep it elevated. I wouldnt know if that works or not , might encourage them to walk on it.
The wind here has taken our cover off for the past 8 winters. This is the first year we used a salt system. We opted not to replace the cover this year as it typically is off the pool in shreds before January or it is shredded and deeply under water. I was thinking with all of the salt in the pool water it would not freeze. As long as it was not frozen I did not think the birds would mess around with it as they had left it alone all summer.