ORIGINAL: Todd1700
Use borax instead of salt.
I'll add one other tip. Instead of paying a lot for those little packs of borax that some outdoors stores sell for just this purpose, instead go to the local grocery store and buy you a box of 20 Mule Team Borax laundry detergent. You will get 10 times as much (enough for many birds) for the same price and it works perfectly fine.