What Not to Feed Birds in Winter

Avoid bread, anything salted, anything moldy, desiccated coconut, cooking fat and drippings, and milk. Most of these are not neutral — they cause real harm. In winter the stakes are higher than in summer, because a bird that fills up on empty calories has wasted the short feeding window it had.

The list

Bread — the one everybody gets wrong

Bread is not toxic, and that is why the advice against it never quite lands. The problem is opportunity cost. A bird that fills its crop with white bread has spent its feeding window on something that is mostly starch and water, and in winter that window is a few hours long. It goes into a fifteen-hour freezing night with nothing banked.

Moldy bread is worse and is genuinely dangerous. And bread left on the ground attracts rats. If you have bread going stale, compost it and put out suet.

Salt — actively toxic

Birds are small and cannot process sodium at anything like the levels we tolerate. Salted peanuts, salted crisps, salted popcorn, and anything cooked with salt are all off the list. This includes de-icing salt near a feeding area, and it certainly includes putting salt in a bird bath to stop it freezing, which appears in folk advice and should not.

Mold — dangerous, and easy to create accidentally

Moldy seed, moldy suet and moldy bread can cause fatal respiratory infection. Aspergillosis is a real and well-documented risk at feeders.

The way most people create this problem is not by putting out moldy food deliberately — it is by letting seed sit damp in a feeder through a wet week, or storing a twelve-pack of suet in a humid garage. Buy feeders with drainage and ventilation, and store food dry. The feeder page covers the drainage side.

Desiccated coconut — swells after eating

Dried, shredded coconut absorbs moisture and can swell inside a bird after it is eaten. Fresh coconut in the shell is fine and is a good high-fat food; the desiccated kind sold for baking is not.

Cooking fat, bacon grease and drippings

Two problems. Roasting-tin fat is mixed with meat juices and salt, and it goes rancid quickly. It also stays soft at temperatures where rendered suet is firm, which means it smears on feathers — and fat on plumage destroys the trapped-air insulation a bird depends on overnight.

Rendered suet from a proper cake does not do this. That is what rendering is for.

Milk

Birds do not have the enzyme to digest lactose and milk causes serious digestive upset. Hard cheese is a different matter — the lactose is largely gone — and grated hard cheese in small amounts is fine.

The quick table

Things that are fine despite the folklore

• Whole peanuts — fine in a mesh peanut feeder that forces birds to take pieces. Unsalted and unroasted.
• Uncooked rice — harmless. The story about it swelling inside birds is not true.
• Apple and pear — good, and windfalls are ideal for thrushes and waxwings.
• Fat balls — fine, but remove any plastic mesh bag before hanging them; the mesh can trap feet and bills.

What to put out instead

The positive list is on what to feed birds in winter, and the ranked cakes are on the suet roundup. Feeder hygiene is where most of the mold risk actually lives: keeping feeders clear.