Cracked corn: the cheapest bag on the shelf and the most expensive mistake

The short answer

• Corn is the cheapest food per calorie we track and the poorest per gram of fat. Matching the fat in one pound of black oil sunflower takes roughly 9.6 lb of cracked corn, which costs more than five times as much.
• Damp corn grows the mold that produces aflatoxin, and aflatoxin is not removed by drying, freezing or sorting. Corn that has been rained on gets thrown away, not dried out.
• Of the five species that rate corn a top-tier food in our dataset, three are birds most people are trying to have fewer of. The other two are the Mourning Dove and the Blue Jay.
• Fine crack spoils fastest and suits the smallest ground birds; medium crack is the sensible default; whole kernels feed jays, doves and squirrels and little else.
• If you use corn, run it as a separate low-volume ground station well away from your seed feeders, and clear it before dark every day.

Cracked corn is field corn dried and broken into pieces. It costs less per pound than anything else sold as bird food, and per raw calorie it is unbeatable: roughly 2,208 kcal delivered per dollar in our food dataset, against 1,472 for black oil sunflower and 591 for nyjer. On that number alone it looks like the smartest purchase in the store.

Calories are the wrong unit. A bird at a feeder in February is not short of starch, it is short of fat, and corn has almost none.

The number that actually decides it#

Cracked corn is about 4% fat. Black oil sunflower kernel is about 51%. Work the two through a pound of each as bought.

To put the same fat into the yard as one pound of black oil sunflower, you need roughly 9.6 lb of cracked corn, and that costs more than five times as much. Corn is the cheapest way to buy bulk and one of the most expensive ways to buy the thing birds are actually at your feeder for. The per-calorie method and the underlying figures are set out in cost per calorie.

That is the honest case against corn. It is not that it is bad food. It is that it is the wrong food to be the bulk of your station.

Aflatoxin, and why corn gets rules the other seeds do not#

Aspergillus molds grow on damp grain in warm conditions and some strains produce aflatoxin. Corn is the grain most associated with it, because the kernels are large and starchy and cracking them exposes the interior. Wild birds are sensitive to it, and the exposure that matters at a feeder is not one bad mouthful but a station that keeps offering slightly moldy grain week after week.

Feed-grade corn is not held to the standard applied to corn intended for people, so the bag on the farm store shelf carries no assurance you can lean on. What you can control is everything after the bag:

• Buy in quantities you will use within about a month, in cool weather, and less in summer.
• Open the bag and smell it. Fresh corn smells faintly sweet and dusty. Musty, sour, or a fermented smell means it does not go out.
• Look at the fines in the bottom of the bag. Gray-green or olive powder clinging to the broken pieces is a stop signal.
• Decant into a sealed, rodent-proof, opaque container. Never store the paper sack on a garage floor, which is where condensation collects.
• Discard everything left in the tray after rain. Not tomorrow. That day.

Corn is the food that makes moldy seed a real hazard rather than an aesthetic one, and storing birdseed covers the container and temperature side in more depth.

The guest list you did not write#

Corn's second problem is that it is a broadcast invitation. Deer, raccoons, rats, mice, squirrels, feral pigs and, in the mountain West and much of Canada, bears all treat corn as a preferred food. So do blackbird flocks, and a grackle flock that finds corn on the ground will bring the rest of the roost with it inside a week.

The management pages for each of those problems assume you have already dealt with the corn, because it is nearly always the first thing to remove: deer at feeders, rats and mice, grackles and blackbirds and, if you are anywhere with a bear population, bears.

Crack size is not a detail#

Corn is sold in three grades and they behave differently enough that picking the wrong one is most of the reason a corn station fails.

• Fine crack (pieces around 1/8 in, sometimes sold as chick-size). The only grade small sparrows and juncos handle easily. It also has the most broken surface per pound, so it takes up humidity fastest and is the first to mold. Treat fine crack as a same-day food only.
• Medium crack (around 1/4 in). The sensible default. Doves, jays, towhees, sparrows and juncos can all manage it, and it holds up through a cold dry day without turning to paste.
• Coarse or whole kernels. Slowest to spoil, and the only grade worth using in wet climates, but the audience narrows to jays, doves and squirrels. If you want to distract squirrels away from a seed feeder, whole corn on a stump does that job and fine crack does not.

A practical marker: if the corn in the bag is more dust than pieces, it has been handled hard and it will cake. Put it back.

Where corn earns its keep#

There is one setup where corn is genuinely useful, and it is not the feeder.

Run a separate ground station, 30 ft or more from your seed feeders, out of sight of them if your yard allows it. Use a shallow tray with a mesh floor rather than bare soil. Put out a measured amount, start with one cup, in the morning. Sweep or lift the tray before dusk. Nothing stays out overnight.

That arrangement does three useful things:

1. It gives Blue Jays and Mourning Doves somewhere to be that is not on top of your sunflower.
2. It concentrates the mess and the mold risk in one spot you can clean rather than spreading it under the feeders.
3. It keeps the ground-feeder crowd separated from the tube and suet birds, which reduces the crowding and the disease pressure at the busy feeder. Placement logic is in where to put a bird feeder and the tray designs that survive a winter are in ground feeders.

What corn should never do is share a container with anything else. In a hopper it absorbs humidity and cements the base. In a tube it gets swept out of the ports. In a mix it is paid for at the blended price and then thrown on the ground by birds that did not want it, which is the mechanism behind most of the complaints in birdseed mixes.

Who eats it#

• Top-tier favorite for: Blue Jay, Mourning Dove, House Sparrow, Common Grackle, Red-winged Blackbird
• Eaten readily by: Dark-eyed Junco, White-throated Sparrow, Song Sparrow, Eastern Towhee, Steller's Jay, California Scrub-Jay, European Starling
• Taken occasionally by: Northern Cardinal, Red-bellied Woodpecker, Northern Flicker

Read the top of that list carefully. Five species rate cracked corn a top-tier food, and three of them are the birds most people are trying to have fewer of: House Sparrow, Common Grackle and Red-winged Blackbird, with European Starling one grade behind. The other two are the Mourning Dove, which most people are happy to feed, and the Blue Jay, which is the one unambiguously welcome enthusiast.

Compare that with the list for black oil sunflower, where nine species rate it top-tier and every one of them is a bird most people are trying to attract. That contrast, more than any nutritional argument, is the reason corn sits at the bottom of our recommended list rather than being left off it entirely. If starlings are already your main problem, starlings explains why removing corn is step one.

Frequently asked questions#

Is cracked corn bad for birds?

Clean, dry cracked corn is not harmful and a number of species eat it readily. Two things make it a poor default. First, it is low in fat and protein, so it delivers bulk rather than the energy birds need in cold weather. Second, corn is the grain most prone to Aspergillus mold, which produces aflatoxin, and aflatoxin can kill birds at levels you cannot see or smell. The food is fine. The failure mode is storage and weather, and corn is far less forgiving of both than sunflower.

What is aflatoxin and why does corn get it?

Aflatoxin is a toxin produced by Aspergillus molds, which grow readily on damp grain in warm conditions. Corn is the classic host because the kernels are large, starchy and often cracked open, giving mold an easy surface. The toxin is heat stable and it survives drying, freezing and washing, so once a batch is contaminated there is no rescuing it. This is why the rule with corn is prevention: keep it bone dry, buy small, and discard anything that gets wet or smells musty.

Does cracked corn attract rats and deer?

Yes, more reliably than any other feeder food. Corn is the standard bait for deer and it is a preferred food for rats, mice, raccoons and, in bear country, bears. Some states and provinces regulate or prohibit deer feeding because of disease transmission, and a corn station in the yard can count. Check your state or provincial wildlife agency before putting corn on the ground, and never leave it out overnight.

Fine or medium cracked corn, which should I buy?

Medium for a general ground station. Fine crack has more broken surface per pound, so it takes up moisture faster and molds sooner, but it is the only grade small sparrows and juncos can handle comfortably. Coarse or whole kernels last longest in the weather but only jays, doves and squirrels bother with them. If you buy fine crack, treat it as a same-day food: put out a cup, watch it go, and sweep up whatever is left.

Can I mix cracked corn into my seed?

You can, and it is why a lot of cheap mixes cost what they do, but it is the wrong place for it. Corn in a hanging feeder gets swept out by birds reaching past it, then sits in the wet grass underneath and molds. Corn in a hopper absorbs humidity and cakes into the base. If corn is going out at all it should go out on its own, in its own spot, in a quantity you control.

Why do so many birds ignore cracked corn?

Because it is a starch, and most feeder birds in winter are shopping for fat. Chickadees, titmice, nuthatches, woodpeckers, goldfinches and siskins all score corn at zero or one in our preference data. The birds that do take it, doves, jays, blackbirds and house sparrows, are large-bodied or flocking ground foragers that handle bulk grain well. That mismatch is the practical argument against corn, not any safety issue.

Sources and further reading

1. National Wildlife Health Center United States Geological Survey Wildlife disease including mycotoxin poisoning in wild birds
2. Feeding Birds: seed types and preferences Cornell Lab of Ornithology, Project FeederWatch Which species take corn and at which feeders
3. Penn State Extension Pennsylvania State University Grain storage and mold management in stored corn
4. Bird Feeding and Care National Audubon Society Feeder food selection and placement