I don't know if this might be helpful or not ..
About 2 yrs. ago, I purchased a "Food Saver" machine .. also known as "Seal A Meal".
I originally purchased it for human foods that I bought in large quantities, but wanted to portion out and freeze.
I found that it works wonderfully with bird foods as well. I was always nervous about buying large bags of anything, because I felt that once the bag is open .. there really is no way to keep it fresh .. not even with Ziplocs/Tupperware .. etc.
The Food Saver creates a vacuum seal, I can tell there is a HUGE difference with foods simply stored with a Ziploc/tupperware and foods stored in a Food Saver sealed bag.
Now, any "bulk" foods I purchase for the birds gets portioned out, and vacuum sealed with the Food Saver. For example .. I buy a lot of freeze dried/dehydrated fruits/veggies. I did a test. I put a portion in a ziploc, a portion in tupperware, and a portion in vacuum sealed bags. After a week, all the but the vacuum sealed bag had gotten sticky and soft, while the vacuum sealed bag was still crisp and firm.
So now, I only have food in ziploc and tupperware that will be used within a week, everything else gets put in the Food Saver vacuum sealed bags.
Just throwing out an idea for those who want to buy in larger quantities, but are nervous about it staying fresh.