A 40-pound bag of sunflower is the cheapest way to buy bird seed, and it’s also the reason there’s a mouse in the garage and a smell coming from the corner. Seed is food. Left in its paper or plastic bag it goes stale in about two months, moldy after one damp week, and it gets found by mice, rats, squirrels, raccoons and pantry moths, all of which chew straight through the bag. Storing it right costs little and takes ten minutes.
The short version
- Store seed in a galvanized steel can with a lid (6 gallons, holds about 40 lb of sunflower). Metal is the only thing rodents can’t chew.
- Indoors, or in a garage that stays dry, a wheeled airtight bin (30 lb) is easier to move and pour from; it’s plastic, so it’s for spaces mice can’t already reach.
- A 4-cup seed scoop with a spout fills tube feeders without spilling half the seed.
- Buy no more than two months’ worth, keep it cool and dry, and toss anything that clumps, smells musty or has webbing in it.
How fast seed goes bad
Sunflower and safflower are oily seeds, and oil goes rancid. At room temperature in a sealed container, black-oil sunflower is fine for three to four months; in a hot garage, closer to six weeks. Nyjer is worse, drying out and losing its oil within a month or two of the bag being opened, which is why goldfinches abandon a feeder full of “perfectly good” seed. Hulled seed (sunflower chips, no-mess blends) has no shell to protect it and spoils fastest of all. Suet cakes keep for months wrapped, but soften and go rancid above about 70°F.
Moisture is the other enemy. Seed that gets damp grows mold within days, and moldy seed carries aflatoxin, which kills birds. If a bag has been rained on or the bottom of the can is clumped, throw it out; there’s no drying it.
What to store it in
Galvanized steel can — the right answer for a garage or shed
6 gallons · lid
A plain galvanized can with a tight lid is what every feed store and every serious feeder uses, because it’s the one container a rat can’t get into. Six gallons holds a 40-pound bag of sunflower with room to spare. Set it on a couple of bricks or a pallet so it’s off the concrete, where condensation collects, and keep the lid on. For two kinds of seed, buy two cans; mixing in one can means the nyjer goes stale at the bottom. A locking-lid version is worth it if raccoons visit.
Downside: heavy when full, and the lid can rust if it lives outdoors. Keep it under cover.
IRIS airtight rolling bin — for indoors
30 lb · wheels
Sold as a dog-food bin, and it works for seed: the gasketed lid keeps seed fresh and pantry moths out, and the wheels mean you roll it to the door instead of carrying it. Use it in a mudroom, a basement or a garage that’s already mouse-free. Clear enough to see how much is left.
Downside: it’s plastic. A determined mouse or squirrel will chew a corner, so it’s not the answer for a shed or a garage with a gap under the door.
Seed scoop with a spout — the cheap fix that ends the mess
4 cups
A scoop that closes at the bottom and opens over the feeder port. Fills a tube feeder in one motion with nothing on the ground, which matters because spilled seed under the feeder is exactly what draws mice and rats in the first place. Any 4-cup scoop works; this is the one that doesn’t crack in the cold.
Where to keep it
Cool, dry and dark, in that order. A basement or an interior closet is ideal. An attached garage is fine in a metal can. A shed or an outdoor deck box is the worst place: temperature swings, humidity and every animal in the neighborhood. Never store seed in the original bag inside a plastic tote and call it done; the tote keeps the smell in and the mice out for about a week.
Buy less, more often
The 40-pound bag is only a bargain if you use it in two months. For one or two feeders, that’s about right for sunflower in winter and too much in summer, when feeding drops by half. Nyjer and hulled seed should be bought in 5-pound bags no matter how big the flock. Check the “best by” date on the bag; big-box stores sell seed that’s already six months old. And write the date on the can with a marker when you fill it, because “I think it’s from spring” is how a can of rancid seed sits until fall. Our seed-by-season guide covers how much of each seed you actually need in each part of the year.
Signs it’s gone
- Smell. Fresh sunflower smells faintly nutty. Rancid seed smells like old paint or crayons. Trust your nose.
- Clumping or a dusty gray coating. Mold. Throw the whole batch out and wash the can with a 10 percent bleach solution.
- Webbing, small moths, or tiny holes in the seed. Indian meal moths. Freeze new bags for four days before storing to kill eggs, and clean the container.
- Sprouting seed under the feeder that the birds ignore. That’s not spoiled, it’s filler (milo, wheat, cracked corn). Buy a better bag.
- Birds stop coming to a feeder that’s been full for weeks. Dump it, wash it, refill with fresh. They come back.
Stored seed draws mice, and spilled seed draws bigger visitors; see will skunks eat bird seed.
Bottom line
One galvanized can on bricks in the garage, seed bought two months at a time, a scoop so nothing hits the floor, and a date written on the lid. That’s the whole system, and it’s the difference between a feeder that’s busy in February and a garage that has mice.
Related: The best bird seed for each season · Keeping squirrels off feeders · Will skunks eat bird seed?
