What not to feed birds, and exactly what goes wrong

The short answer

• Bread is not poison, it is dilution: it fills a crop with starch that displaces the fat, protein and calcium a bird actually needs, and it molds within a day once wet.
• Salt, chocolate and avocado are dose problems. A bird weighing 15 to 50 g gets an enormous per-kilogram dose from a scrap that looks trivial to you.
• Milk fails because birds have no meaningful lactase. Undigested lactose ferments in the gut and causes serious digestive upset.
• Mold is the item on this list most likely to actually kill. Aspergillus in damp seed causes fatal respiratory infection, and moldy peanuts and corn can carry aflatoxins.
• Uncooked rice is harmless to birds. The wedding-rice story is false, and rice fields feed enormous numbers of wild birds every year.

Most "do not feed" lists are just lists, and a list is easy to override at 7am when you have stale bread and a lawn full of sparrows. So this page gives the mechanism for each item. Once you know what a food actually does inside a bird, the exceptions stop being tempting.

Four ways a food goes wrong#

Nearly everything on this page fails through one of these, and some fail through several.

Body mass is the thread running through the middle two. A Black-capped Chickadee weighs about 11 g. A Northern Cardinal is about 45 g. A crisp, a square of chocolate or a smear of salted butter that reads as a nibble to you is, per unit of body weight, a serving that has no human equivalent.

Human staples: bread, milk and salt#

Bread and baked goods#

Bread is not poison. Bread is dilution. Refined starch fills a crop with calories that carry almost no fat, very little usable protein and no calcium, and a bird that arrives at dusk with a crop full of bread has spent its last feeding opportunity of the day on something that will not get it through a cold night. In nestlings the effect is worse, because they are building bone and feather from what the parents bring in.

Three secondary problems make it worse than the nutrition alone suggests:

• Wet bread grows mold within a day, and mold is the genuinely dangerous item further down this page.
• Uneaten bread on the ground is a reliable way to establish rats and mice at a feeding station.
• Bread thrown into ponds fouls the water and concentrates waterfowl in unnaturally dense, disease-friendly groups.

The same applies to crackers, breakfast cereal, cake, doughnuts and pastry, with added salt and sugar in most cases.

Milk and dairy#

Birds are not mammals and do not produce meaningful amounts of lactase. Lactose that cannot be split passes into the gut undigested, where it draws water into the intestine and ferments. The result is diarrhoea and serious digestive upset in a small animal with very little margin for fluid loss. Milk-soaked bread, a favorite in old bird-feeding advice, manages to combine this with the displacement problem above.

Hard cheese is the partial exception people ask about: it is very low in lactose, and small amounts of mild grated cheese are taken by robins and wrens. It is still fatty and salty enough that there is no reason to prefer it to suet.

Salt and seasoning#

Birds regulate sodium with far less headroom than mammals, and their kidneys have limited capacity to excrete an excess. A sodium load pulls water out of the tissues, and dehydration in a bird that may not have access to open water in winter is a fast-moving problem.

So: no salted peanuts, no crisps, no salted popcorn, no bacon, no salted butter, no seasoned leftovers. Onion and garlic bring their own problems on top of the salt. If a food came out of a packet with a flavor on it, it is not bird food. Plain unsalted nuts are the version to buy, and the detail is in peanuts for birds.

Raw meat, grease and the rendering difference#

Raw meat is a bacterial culture at ambient temperature. Left in a feeder it spoils within hours in warm weather, and it reliably draws raccoons, rats, cats and, in some regions, bears. It also puts uncooked animal protein into a place where many birds feed in succession, which is exactly the transmission pattern described in bird diseases at feeders.

Unrendered kitchen fat, bacon grease and cooking oil fail differently. They stay soft or liquid at ambient temperature and smear onto plumage. Grease in feathers destroys the interlocking barbule structure that makes a feather waterproof and insulating, and a bird cannot preen it out. In cold or wet weather that is life-threatening.

Rendered suet is not the same material. It has been melted, strained of meat and connective tissue, and re-set so it is firm at ambient temperature, holds together in a cage, and does not transfer to feathers. That processing is the entire difference between a good winter food and a bad one. In hot weather even proper suet softens and goes rancid, which is why summer calls for no-melt formulations or none at all.

Avocado, chocolate and desiccated coconut#

Avocado. Contains persin, in the flesh, skin, pit and leaves. It is well documented as toxic to a range of bird species, with heart muscle damage and respiratory distress among the effects, and sensitivity varies unpredictably between species. Nobody has a reason to put avocado out, so there is no argument to weigh against the risk. That includes guacamole scraps and skins on an open compost heap.

Chocolate. Theobromine and caffeine are methylxanthines that birds clear slowly. The effects are cardiac and neurological. Dark chocolate carries more theobromine than milk chocolate, but the safe amount is zero in both cases. Coffee grounds and tea leaves belong in the same category for the same reason.

Desiccated coconut. The standard advice is to avoid dried, shredded coconut, on the grounds that it absorbs moisture and swells after being swallowed. Fresh coconut in the half shell is commonly offered and is a different proposition, though it goes rancid and grows mold quickly in warm weather and should be replaced every couple of days. Never offer coconut that has been sweetened or salted.

What goes into a hummingbird feeder and should not#

Nectar feeders concentrate risk because a hummingbird drinks a very large volume relative to its body mass every day. Anything dissolved in the mix is consumed at a rate nothing else at your feeders comes close to.

• Honey water. Honey is not simple sucrose. It carries wild yeasts and spores, and diluted in water it cultures yeast and mold far faster than sugar water. A honey feeder in summer becomes a growth medium in a day or two.
• Brown, raw or turbinado sugar, molasses, maple syrup. These retain or add molasses, which carries iron and other minerals, and there is no reason to introduce a mineral load into a bird that drinks its body weight in liquid.
• Artificial sweetener. Tastes like food, delivers no calories. The bird feeds and gets nothing, at the time of day it can least afford it.
• Red dye. No nutritional value and no attraction benefit, because hummingbirds find feeders by the red on the hardware. When the upside is exactly zero, any uncertainty about the additive settles the question.

The correct mix, the change intervals and the honest answer on boiling are all in the hummingbird nectar recipe.

Mold is the one that actually kills#

If you only act on one item on this page, act on this one. Everything above is a bad idea. Mold is an active cause of death at feeders every year.

Aspergillus fumigatus grows readily in damp seed, in the caked plug at the bottom of a tube feeder, and in wet hulls on the ground. Birds inhale the spores while feeding and develop aspergillosis, a respiratory infection that is frequently fatal and cannot be treated in the wild. Separately, Aspergillus flavus growing on peanuts and corn produces aflatoxins, which damage the liver and are dangerous at very low concentrations.

Practical rules that follow from that:

• Never put out seed that smells musty, looks clumped, or has visible white, gray or green growth. See moldy seed for what to look for.
• Never top up a feeder over old seed. Empty it, then refill.
• Peanuts and cracked corn are the highest-risk items because they support aflatoxin-producing molds particularly well. Buy them in quantities you will use in weeks, not months, and keep them dry, as covered in storing birdseed.
• Rake up hulls and spilled seed under feeders, especially after a wet spell.
• Wash feeders on a schedule using the method in how to clean a bird feeder.

Rice is fine, and the wedding story is false#

The claim is that uncooked rice absorbs water in a bird's stomach, swells and kills it, which is why rice was supposedly banned at weddings. It is not true.

Birds eat dry seed constantly, including grains that take up water. Rice is a grass seed like any other. Rice fields across North America and Asia feed enormous numbers of wild birds every season, blackbirds and doves eat waste rice in harvested fields as a matter of routine, and waterfowl feed in flooded paddies in vast flocks. If dry rice worked the way the story claims, this would be extremely obvious.

Plain cooked rice with nothing added is also fine, and robins and starlings will take it. Neither form is a particularly valuable feeder food: rice is low in fat and unexceptional in protein, so cracked corn or millet does the same job better on a ground tray. The point is only that this is a myth, and it belongs with the others in bird feeding myths.

What to put out instead#

Everything on the list above has a straightforward replacement, and the replacements are cheaper per bird than kitchen scraps are convenient.

Prices are 2026 United States big-bag benchmarks used as defaults in our seed cost calculator. Swap in your own and the ranking can change; the edible fraction and energy columns will not.

For the stale bread instinct in particular, the honest substitute is fat: suet in winter, plain unsalted peanuts year round. Both give a bird what bread pretends to give it. If you are setting up from scratch and want the order to buy things in, start with which seed to buy.

Frequently asked questions#

Is bread really bad for birds?

Bread is not toxic, it is empty. A crop full of white bread is a crop that is not full of fat, protein or calcium, and for a growing nestling or a bird facing a freezing night that displacement matters. It is worse than it looks in three other ways: wet bread grows mold within a day, uneaten bread draws rats and gulls, and floating bread fouls the water in ponds. An occasional crumb from a sandwich will not kill a robin. A daily loaf on the lawn is a genuinely bad feeding station.

Can birds eat chocolate?

No. Chocolate contains theobromine and caffeine, both methylxanthines, and birds metabolize them slowly. The effects are cardiac and neurological: raised heart rate, tremors, seizures. Because the dose that matters is per unit of body weight, a piece of chocolate that would not register in a person is a substantial dose for a bird of 20 or 40 g. Dark chocolate carries more theobromine than milk chocolate. There is no safe serving and no reason to find one.

Why is avocado dangerous for birds?

Avocado contains persin, present in the flesh, skin, pit and leaves. It is well documented as toxic to a range of bird species, causing heart muscle damage and respiratory distress, and sensitivity varies by species in ways nobody can predict for the wild birds in a given yard. Since there is no nutritional argument for putting avocado out in the first place, the sensible position is total avoidance, including guacamole scraps and avocado skins on a compost heap birds can reach.

Can I use honey instead of sugar for hummingbirds?

No. Honey is not simple sucrose: it carries its own wild yeasts and spores, and diluted in water it cultures yeast and mold far faster than sugar water does. A honey water feeder in warm weather becomes a growth medium within a day or two, and a hummingbird feeding repeatedly at fungal growth is at real risk. Use plain white granulated sugar at four parts water to one part sugar, with no dye and nothing else added.

Does uncooked rice kill birds?

No. The claim that rice swells inside a bird and bursts its stomach is false. Birds eat dry seeds constantly, including grains that absorb water, and rice is no different. Enormous numbers of wild birds feed in rice fields every year, and blackbirds, doves and waterfowl take rice as a normal food. The wedding-rice story appears to have been invented rather than observed. Rice is not a particularly valuable feeder food, but it is not a hazard.

What about bacon grease and kitchen fat?

Leave both out. Bacon fat is heavily salted and carries meat residues, so it fails on the salt count and goes rancid quickly. Soft unrendered fats and cooking oils smear onto feathers, and grease in plumage destroys the interlocking structure that keeps a bird waterproof and insulated. Rendered suet is a different material: it has been melted, strained and re-set so it is firm at ambient temperature, holds its shape and does not coat feathers in the same way.

Sources and further reading

1. Feeding Birds Cornell Lab of Ornithology, Project FeederWatch Appropriate feeder foods, foods to avoid, and preventing mold and disease at feeders
2. National Wildlife Health Center U.S. Geological Survey Aspergillosis and mycotoxins in moldy feed
3. How to Make Hummingbird Nectar National Audubon Society No honey, no dye, plain white sugar only