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Stored cool, dry and sealed, most bird seed keeps for several months — but always go by the best-before date on the bag. Oily seeds like sunflower hearts go stale faster than whole seed, and peanuts must be kept bone dry because damp ones can develop aflatoxin, a mould toxin that can kill birds. If food smells musty, looks clumped, dusty or discoloured, bin it.
- Check first: the best-before date on the packet.
- Store: airtight metal or thick plastic bin, cool, dry, off the floor.
- Biggest risk: damp — mould and aflatoxin.
- Second risk: mice, rats and pantry moths.
- Buy: only what you’ll use in a couple of months.
How long each food keeps
These are general guides for unopened and well-stored food. Manufacturer dates come first.
| Food | Typical storage life | Notes |
|---|---|---|
| Whole seed mixes | Several months to a year | Husks help protect the seed |
| Sunflower hearts | A few months once opened | Oils go rancid; smell before using |
| Nyjer seed | Several months | Stale nyjer is a common reason goldfinches ignore a feeder |
| Peanuts | Use within a few months | Buy from suppliers who test for aflatoxin |
| Fat balls and suet | Follow the date; keep cool | Rancid fat smells sharp and soapy |
| Dried mealworms | Many months sealed | Watch for moths and mites |
The aflatoxin warning
Aflatoxin is produced by moulds that grow on peanuts and some grains in warm, damp conditions. It is highly toxic to birds. Buy peanuts from a reputable bird-food supplier, keep them completely dry, and never feed peanuts that look shrivelled, discoloured or mouldy. Salted or roasted peanuts should never be used either.
How to store bird food properly
- Use a sealed bin. A galvanised metal bin or a thick plastic container with a tight lid keeps out damp and rodents. Mice chew through bags and thin plastic.
- Keep it off the floor. Stand it on a shelf or pallet in a shed or garage, out of direct sun.
- Keep it cool. Heat speeds up the oils turning rancid, so avoid a greenhouse or sunny porch.
- Don’t mix old and new. Finish the old batch or throw it away before adding a fresh bag on top.
- Keep the bag inside the bin. That way you still have the best-before date and batch details.
- Clean the bin between batches. Wash, dry thoroughly, then refill.
Tip: scoop food with a dedicated jug rather than your hands, and keep the scoop inside the bin so it stays dry.
Signs bird food has gone off
- Smell: musty, sour or paint-like (rancid oil).
- Look: clumps, webbing, fine dust, green, grey or black patches.
- Movement: small moths, larvae or mites in the bag.
- Behaviour: birds that used to empty a feeder suddenly ignore it.
If in doubt, throw it out — bag it and put it in the general waste, not the garden, so it doesn’t feed rats.
Food in the feeder goes off faster
Storage life means nothing once seed is sitting in a feeder in the rain. Wet seed in the bottom of a tube can go mouldy within days. Put in only what gets eaten in a day or two, check the base of tube feeders for clumped seed, and follow current RSPB advice to clean feeders weekly.
Autumn restock: with seed and peanuts paused under RSPB guidance until 31 October, check any bags left over from last winter before November. Food that has sat in a shed all summer is often past its best.
Common questions
Can I use bird seed past its best-before date?
Best-before is about quality, not a hard cut-off. If it’s been kept dry, smells fresh and looks clean, a little past the date is usually fine. Anything musty goes in the bin.
Can I freeze bird seed?
Freezing for a few days kills moth eggs and larvae. Let it return to room temperature in a sealed container so condensation doesn’t form on the seed.
Is it worth buying bird food in bulk?
Only if you’ll use it within a couple of months and have a sealed bin to keep it in. Otherwise the savings are lost to waste.
Why is my seed full of little moths?
Indian meal moths. Throw the affected food away, clean the container thoroughly and store new food sealed.
Related guides
- Are peanuts safe for birds?
- How to clean bird feeders
- Why nyjer seed isn’t being eaten
- Feeding birds on a budget
Sources: RSPB garden bird feeding guidance (April 2026 update); BTO guidance on food safety and aflatoxin; Birdcare Standards Association guidance on peanut testing.
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