Bird Food

Is Bird Seed Tested for Aflatoxin?

Not by any US or Canadian rule we could find. The 20 ppb "legal limit" is a non-binding FDA action level, Texas lets wildlife feed carry 50 ppb under a warning, and Canada's feed law does not reach wild birds. The rule in each place, what testing found in the bag, and how to buy around it.

Bird seed is not routinely tested for aflatoxin, and nothing in the US federal guidance, the Texas feed rules or Canada's feed regulations requires a bag sold for backyard birds to be tested before sale. Aflatoxin is the liver toxin made by Aspergillus molds on corn, peanuts and other grain. Some manufacturers screen for it, so whether your bag was checked depends on the brand, not the law. Bird seed falls into a similar gap for weed seed.

The figure quoted everywhere is 20 ppb (20 micrograms per kilogram). A widely repeated 2007 news summary of a University of Guelph review calls it the "legal limit" in the US and Canada. For wild bird seed, that is wrong in both countries, for different reasons.

The rule in each place#

We read the primary text for each. The number barely changes; what changes is whether it binds anyone and whether it covers seed for wild birds at all.

Note the units. The US and Canadian figures count all four aflatoxins together; the British limit counts B1 alone, so one reading can pass in one country and fail in another.

Why 20 ppb is not a legal limit#

The FDA set 20 ppb for all foods, animal food included, in 1969. Its current compliance policy guide keeps 20 ppb for immature animals, pets, dairy animals and "other animal species (including wildlife), or other uses not specified". Only named livestock get more: 100 ppb for breeding cattle, breeding swine and mature poultry, 200 ppb for finishing swine, 300 ppb for feedlot cattle.

The same document says action levels "are not binding on the courts, the regulated industry, or the agency". To act, the FDA must confirm the intended use and show the level supports a charge of adulteration, and the guide allows that enforcement may be warranted below the line or not warranted above it. So 20 ppb is where FDA staff are told to escalate, not a line a seller must test against. The number is right; calling it a legal limit, and assuming someone checks bird seed against it, is what goes wrong.

Texas: 50 ppb with a warning

Texas lists grain and oilseed products over 20 ppb as a poisonous or deleterious substance under 4 TAC §61.61, "except that with proper labeling", less than 50 ppb "may be distributed when destined for wildlife". That bag must carry a statement similar to "WARNING: Product contains less than 50 ppb aflatoxin. Not for lactating dairy animals. Not for human use."

The rule also lets the seller print "Meets the Texas Standard for Wildlife Feed" next to that warning, or on a product under 20 ppb with no warning at all. The phrase does not tell you which side of 20 ppb the bag is on. The warning does. So the one state rule here with a wildlife number permits more aflatoxin in wildlife feed, not less. If you feed birds in the state, the Texas feeding guide covers the rest of the local picture.

Canada: wild birds are not livestock

Canada's Feeds Act covers feed for "livestock", meaning animals designated by regulation. The Feeds Regulations, 2024 designate animals "domestically raised or kept": cattle, sheep, goats, bison, cervids, swine, poultry, horses, rabbits, bees, food fish and shellfish, plus pigeons, pheasants, partridges, quail, grouse, guinea fowl, pea fowl and ratites. Chickadees at a backyard feeder are neither kept nor listed, and we found no CFIA standard written for wild bird seed.

What testing has found in the bag#

Three surveys have measured aflatoxin in food sold for wild birds or wildlife, and one review pulled earlier surveys together. They point at the same ingredients.

In the Texas survey, grocery store bags averaged under 20 ppb in four of five regions, while cooperative bags in the south and west averaged more. That was 1999: a reason to ask about storage, not a ranking of stores today.

The British study adds the ingredient detail. Peanut granules were much more likely than whole peanuts to carry aflatoxin, branded and unbranded peanuts did not differ significantly, and sunflower hearts were the least likely food tested. The authors also cite earlier British work in which food residues from seven garden feeders all held aflatoxin, two of them at 690 and 61,710 ppb.

How much harms a bird#

Almost no dosing work exists for songbirds, which is why the regulatory numbers come from poultry and livestock. What there is:

• Northern bobwhite (2013). Wild-caught quail dosed weekly for four weeks at 100 to 2,000 ppb died in every treated group except 100 ppb, and the authors concluded doses "as low as 100 ppb can be detrimental".
• Northern cardinal (2019). A book chapter by the same Texas group, as reported by the British team, put the lethal dose for half of adult cardinals at about 500 ppb in feed, with immune suppression at as little as 25 ppb.
• Choosing food. In trials cited by the 2001 paper, white-winged doves and bobwhites did not avoid contaminated feed, while green jays did.

Set the rules against those figures: 20 ppb sits just under the 25 ppb at which cardinals showed immune effects, the Texas 50 ppb allowance sits above it, and the worst surveyed bags were many times past 100 ppb.

Buying around it#

1. Read the first three ingredients. Corn was the strongest marker of a bad bag in the Texas survey, and reading a seed mix label finds it in seconds.
2. Prefer whole peanuts to granules, served in a peanut feeder the birds clear in a day or two.
3. Lean on sunflower. Hearts and black oil sunflower carried the lowest measured risk.
4. In Texas, read for the warning. "Product contains less than 50 ppb aflatoxin" means 20 to 50 ppb. Put it back. That applies to deer corn too: the 2017 survey found every bag under 20 ppb, but the rule allows 50 with a warning, so check before feeding turkeys or doves.
5. Ask for the number. Some brands state their product is tested for aflatoxins. If yours does not, ask what is tested, how often and to what level, and, as the British team suggests, where the seed was stored.

At home, the British team's precautions match the rest of this site: buy what you will use within about three months, store it sealed, cool and dry as in storing bird seed, and fill feeders with what birds eat in one to two days rather than topping up. Bin the residue at the bottom of a feeder, throw out anything damp or caked as covered in moldy, clumped or wet seed, and clean the feeder on a regular schedule.

Does aflatoxin form after purchase? In the British experiment, peanuts left outdoors through spring and summer, or kept in storage, showed no significant rise over point-of-sale levels, and Texas corn held in deer feeders for a year averaged under 5 ppb. But the highest reading in any source here, 61,710 ppb, came from residue left in a garden feeder. That is the argument for emptying it.

What this page cannot tell you#

We read the federal guidance and the rules for Texas, Canada and Great Britain, not the feed rules of the other 49 states; your state agriculture department's feed program can tell you yours. The surveys are old (bags bought in 1999, 2007 and 2018), so they show that bagged bird food can carry aflatoxin well above 20 ppb, not what share of today's bags does. And the songbird toxicity evidence is one quail study we read directly and one cardinal chapter known through the British paper, whose authors say the clinical significance for wild birds "requires further investigation".