I used to store my BOSS outside in a metal trash can. I never had mold, but one year fire ants built a nest in it. I had to dump it all. $$I am kitty sitting for my neighbor for the next couple weeks, she told me to feed the birds if I wanted to but don't have to.. so I went out on the deck where the boss is kept in a metal garbage can took the lid off and grabbed the scoop, then noticed the seeds were moldy and I saw some kind of worm! grossed out I slammed the lid back on and said to myself, no way!the birds can eat insects so they will be fine, it's not winter after all. The bird feeder had been full when the neighbors left so they must have just filled it, the seeds in the can didn't mold in just a day and a half, did they?? I hope the birds don't get sick from having eaten the moldy seeds!
I keep my birdseed in a shed that is up on blocks, using the same type of can. I've had no insect or mold issues.