Bird Food

What Not to Feed Birds

Most bad bird food is not poison. It is filler that crowds out real nutrition, or it is seed that went bad in your garage. Both do damage quietly.

The short answer: no bread, no salted anything, no chocolate or coffee, no avocado, no onion or garlic, no milk, no dry uncooked beans, no cooking grease, and no seed that smells musty. Everything else is a matter of proportion rather than danger.

That list is shorter than most people expect, and the ranking is not what most people expect either. Outright poisons rarely reach a backyard feeder. What actually harms birds is bulk food with no nutrition in it, and seed that spoiled in a bag in the garage.

Below, each item with the specific reason it matters, then the gray areas that get argued about, and a short list of what to put out instead.

Bread and the rest of the bakery aisle#

Bread, crackers, doughnuts, cake, chips, popcorn and breakfast pastries all share a problem. They deliver refined starch and little else: minimal usable protein, almost no fat of the kind birds store for cold nights, and no calcium at all.

The mechanism is displacement. A chickadee weighs less than half an ounce (about 12 g) and can only hold so much. Filled with bread, it forages less and goes into a cold night short on the fat reserves it needed. Nestlings fed bread by their parents grow poorly on protein they never received.

In waterfowl the damage is more visible. Ducks and geese raised on a high-starch, low-protein diet frequently develop angel wing, where the last joint of the wing twists outward and the bird can never fly. The evidence is observational rather than experimental, but it is consistent enough that no wildlife agency recommends feeding bread to ducks.

Bread also molds within a day or two in the open, which turns a nutrition problem into a fungal one.

Salt and salted nuts#

Salted peanuts, salted sunflower seeds, pretzels, chips and cured meats are all out. Songbirds have very limited ability to shed excess sodium, and a handful of salted nuts contains far more than anything they encounter in a natural diet. Excess salt causes thirst, then dehydration, then kidney damage.

Buy raw, unsalted peanuts for birds and check the packet: dry roasted is fine, seasoned is not. This is also why road salt runoff pooled near a feeder is worth thinking about in winter, and why a clean water source matters. Details in winter water and heated bird baths.

Chocolate and caffeine#

Chocolate contains theobromine, a stimulant alkaloid that birds and dogs both metabolize far more slowly than humans do. It affects the heart and nervous system, and the effective dose for a bird weighing an ounce (28 g) is very small. Coffee grounds, tea bags and caffeinated drinks act on the same pathway.

There is no useful threshold to work with here. Keep chocolate, cocoa, coffee and tea entirely off the tray, including cookies and cake that contain them.

Avocado#

Avocado contains persin, a fungicidal compound present in the flesh, skin, pit and leaves. It is well documented as toxic to caged birds, where it causes heart muscle damage and sudden death, and sensitivity varies a great deal between species.

Nobody has run controlled trials on backyard songbirds, and nobody should. Guacamole and avocado peel do not go on the feeder tray.

Onion, garlic and dry beans#

Onion and garlic contain sulfur compounds that can damage red blood cells in birds and cause anemia. The quantities in a scrap of cooked leftovers are small, but there is no reason to find the threshold.

Dry uncooked beans are a separate and sharper hazard. Raw kidney beans and their relatives contain high levels of a lectin that is genuinely toxic, and it is destroyed only by proper cooking. Dry beans sometimes turn up as cheap filler in low-grade mixes, another reason to read the panel as described in bird seed mixes.

Milk and dairy#

Birds are not mammals and produce essentially no lactase. Milk, cream and soft cheese pass through undigested and can cause severe diarrhea and dehydration in a small bird.

Hard cheese is the partial exception, since aging removes most of the lactose, and grated mild cheddar is a traditional offering for robins and wrens. Even then it is salty, so treat it as a rare small offering rather than a staple. Real insect protein from mealworms does the same job without the compromise.

Moldy, musty or clumped seed#

This is the hazard most likely to be present in your yard right now.

Seed stored warm and damp grows Aspergillus and related molds. Some strains produce aflatoxin, which damages the liver at low concentrations and is genuinely lethal to birds. Corn is especially prone to it, which is why cheap corn-heavy mixes stored badly are a real risk rather than a theoretical one.

The fix is storage, not vigilance: sealed containers, cool and dark, quantities you will use within a month or two. The full method is in storing bird seed, and the diagnosis of seed already gone wrong is in moldy, clumped or wet seed.

Cooking grease, bacon fat and meat scraps#

Rendered beef suet is a legitimate winter food. The fat from your frying pan is not, for three separate reasons.

Salt and additives. Bacon fat carries curing salts, nitrates and smoke residues. Pan drippings carry whatever you seasoned the meat with.

Melting point. Beef suet is hard and stays hard well above freezing. Cooking grease stays soft or semi-liquid, so it smears onto the face and breast feathers of any bird that feeds at it. Matted feathers lose their insulating loft, and a bird cannot preen grease out.

Spoilage. Unrendered fat goes rancid quickly and turns bacterial in warm weather.

If you want to make your own fat cakes, use plain rendered beef suet or unsalted lard and follow the ratios in homemade suet recipes. Store-bought cakes and the temperature limits for offering them are covered in the complete suet guide.

Raw meat scraps sit in a similar category. Jays, crows and starlings will take them, but in warm weather a tray of raw meat becomes a bacterial culture within hours and draws rats, raccoons and flies. If you offer meat at all, offer it in cold weather, in small amounts, and clear it before dark to avoid the problems described under rodents under bird feeders.

The arguments that will not die#

Four items get repeated as dangerous and are not, or are more nuanced than the warning suggests.

Raw rice does not swell inside birds and kill them. It is a myth. Uncooked rice is low-value food and not worth offering, but it is not lethal.

Red dye in hummingbird nectar has never been shown to harm birds. It is also completely unnecessary, since the feeder itself provides the red. Plain white sugar and water, in the proportion given in the hummingbird nectar recipe, is the whole answer.

Honey in nectar is a real problem, though, and gets confused with the dye question. Honey ferments readily and supports mold growth in a feeder, so use white table sugar only. Never brown sugar, raw sugar, molasses or artificial sweetener.

Peanut butter does not glue birds' throats shut. That claim has circulated for decades with no evidence behind it. Offer it in cold weather in a suet log or smeared into bark, and mix it with cornmeal if it makes you more comfortable. In summer heat it goes rancid and drips, which is a better reason to stop.

What to put out instead#

Replacing bad habits with good ones is more effective than a list of prohibitions.

• Instead of bread on the lawn: cracked corn or white millet on a ground tray, in amounts cleared each day.
• Instead of salted nuts: raw unsalted peanut halves in a mesh feeder.
• Instead of bacon grease: a rendered beef suet cake in a proper suet feeder.
• Instead of sweetened cereal or crackers: chopped apple, pear or orange, covered under fruit for birds.
• Instead of cheese for robins and bluebirds: dried or live mealworms.