rodents and bird seed is a problematic mix. you don't have to spill any, the smell will draw them in.
used to keep my bulk in the garage; mice galore. they chewed thru the (original packaging) plastic bags, a fiber drum, chewed a 'notch' out of the top of a plastic tote to get in. then they fall in, can't get out, cats go nuts, interesting surprises when you open the lid... my bet is rodents will chew thru anything wood. I tried patching the fiber drum with aluminum flashing. the mice found it easier/faster? to chew thru the flashing than make a new hole in the fiber drum.
I use a metal can, sealed up the vent hole with caulk to keep any water out. it's a veddy old one - with a wire bail handle to keep it secure - heavy duty. they don't make 'em like that anymore. I keep it outside on the deck which deters mice - but the squirrels & chipmunks still try to chew thru the metal - on a daily basis.
we had an ice storm. squirrels may not get a good grip on flat sheet metal, but ice? no problemo.....