Is Hot Pepper Bird Seed Safe for Birds, and Does It Work?

The short answer

• Hot pepper bird seed is safe for birds as far as the research shows: their capsaicin receptor does not respond to it, so they are indifferent to the burn (Jordt and Julius 2002).
• The one published field test (Ithaca, NY, spring 1999) found gray squirrels took significantly less treated sunflower and spent less time feeding, while bird visits held steady at two sites and rose at the third.
• It did not stop chipmunks. For them, the fix is catching the spill.
• One of the test's four authors worked for the birdseed company whose subsidiary held the EPA registrations, which were addressed to him by name. The result fits the lab work, but nobody independent has repeated it that we found.
• The danger is to you: the labels warn of a strong, temporary irritant to eyes, nose and skin. Wear gloves, add eye protection for feeders at or above eye level, and keep it out of water.

Yes on both counts, with limits. Hot pepper bird seed is safe for birds as far as any study shows, and it does cut how much seed gray squirrels take. Birds do not feel the burn of capsaicin. Squirrels do. The one published field test found squirrels took significantly less treated seed, while bird visits held steady or went up. It did nothing to stop chipmunks.

The catch is how small that test was, and who helped run it. Both are below.

What hot pepper bird seed is#

Hot pepper bird seed is ordinary birdseed coated with capsaicin, the compound that makes chili peppers hot. Labels list it as "capsaicin and related capsaicinoids", the family of hot compounds in peppers. The coating comes from oleoresin of capsicum, an oily extract of hot peppers, or from ground hot peppers. It is sold three ways: as treated seed, as treated suet, and as a powder you mix into your own seed.

Because it is sold to drive an animal away, it counts as a pesticide. In May 1997 EPA registered a treated seed, a treated suet and a mix-in powder under FIFRA, the federal pesticide law.

Two units come up. Parts per million (ppm) is how much capsaicin is on the seed by weight. Scoville Heat Units (SHU) measure how hot it tastes. The field test gives both, and its pairs work out to about 16.5 SHU for each ppm.

Why birds eat it and squirrels avoid it#

Mammals feel capsaicin through a pain sensor in their nerves, the vanilloid receptor. Birds have the same receptor, but capsaicin does not switch it on. A 2002 study in Cell found the chicken version "normally insensitive" to capsaicin. It still responded to heat and acid, just as a rat's does. The authors put it plainly: birds are indifferent to the pain-producing effects of capsaicin.

That is how wild chilies work. A 2001 study in Nature found capsaicin "selectively discourages vertebrate predators" of chilies without deterring the better seed dispersers, the animals that carry seeds away. The Cell paper names those dispersers: birds.

USDA researchers saw the same split in 1991. They gave capsaicin to European starlings and Norway rats in feeding and drinking tests. Synthetic capsaicin was "not repellent to birds". For the rats it was the best repellent of the five compounds they tested.

The one field test, and who ran it#

Paul Curtis and two colleagues in Cornell's Department of Natural Resources ran the test at three sites near Ithaca, New York, from 11 May to 24 June 1999. A fourth author, Joseph Dunn, joined them. The paper appeared in 2000 in the proceedings of the 9th Wildlife Damage Management Conference.

Here is how it was set up, from the paper's abstract:

• Each site had one feeding station with 600 g of whole black oil sunflower in the shell.
• The seed went out for one 3-hour session a day, and what was eaten was weighed.
• Plain seed ran in weeks 1, 2 and 4. Treated seed ran in weeks 3, 5 and 6.
• Observers watched squirrels, birds and chipmunks for the full session, two days a week at each site in most weeks.
• The treated seed measured 40,000 SHU (2,424 ppm) on the shell and 2,000 SHU (121 ppm) on the heart.

And here is what it found:

• Gray squirrels: capsaicin "significantly reduced" both the seed they took and their total time feeding. The drop in time came mainly from shorter visits.
• Birds: visits were unaffected at two sites and rose with treated seed at the third. The mix of species did not change.
• Chipmunks: not deterred.

The abstract gives no percentages, and the full paper would not load for us. So this page does not put a number on the drop.

Now the authors. Dunn was at a Buffalo, New York birdseed company. EPA's May 1997 registration notices for the treated seed, suet and powder all went to that company's squirrel-repellent subsidiary, each marked "Attention: Dr. Joseph A. Dunn." So the only field test of hot pepper seed was co-written by the person the registrations were sent to.

That does not make the result wrong. Cornell staff ran it, and the bird findings match the lab work above. But we found no repeat by anyone without a stake in the product.

One batch, worked through the label numbers#

The EPA records print the capsaicin content of each product. Walk through them and you can see what you would be putting out.

Take one 3 oz packet of the registered mix-in powder. It is 1.08% capsaicinoids by weight.

1. The 1997 label says mix one part with 40 parts seed, so the whole packet goes into 7.5 lb. That gives 1.08% divided by 41, about 0.026%, or about 263 ppm across the batch.
2. A revised label stamped in November 1998 changes the ratio to one part in 120. The same packet now goes into 22.5 lb, which gives about 89 ppm. That is a third of the first strength.
3. The ready-made treated seed in the same records is 0.024%, which is 240 ppm.
4. The treated suet is 0.088%, which is 880 ppm.

The SHU column uses the field test's own ratio of about 16.5 SHU per ppm. The field test figures are for shell and heart separately, with no whole-seed average. So they do not line up row for row with the label percentages.

What they do show is where the heat sat. The shell carried 20 times the capsaicin of the kernel inside it. A cardinal or finch cracks the shell and drops it. A squirrel has to chew through it.

A jar of kitchen cayenne gives no capsaicin figure at all, so a homemade batch has an unknown dose. The site's view on sprinkling it by hand is in stopping squirrels.

Safe for birds is not safe for you#

The safety question keeps coming back because the bag carries a loud warning. All three EPA labels say "Causes moderate eye irritation." They also say "Strong, temporary irritant to eyes, nose and skin." Both sit under Hazards to humans and domestic animals. The warning is about you, your children and your pets. People feel the burn on their own hands and assume the birds feel it too.

The label cannot settle it the other way either. The federal labeling rule, 40 CFR 156.10, lists "safe", "harmless" and "nontoxic to humans and pets" as examples of misbranding on a pesticide label. It also lists "Contains all natural ingredients", and EPA struck that phrase from all three labels in

1. EPA's notices add that registration is not an endorsement. So the bag is not allowed to tell

you it is safe for birds. The evidence for that is the receptor work and the field test.

What the labels tell you to do:

1. Fill on a calm day, so wind does not blow dust into your face.
2. Wear rubber gloves to handle it.
3. Wear eye and face protection when you pour from the bag, or fill a feeder at or above eye level.
4. Mix outdoors, out of the wind, in a container that seals. Never mix indoors or downwind.
5. Wash with soap and water afterward. If it gets in your eyes, flush with plenty of water, and call a doctor if the irritation persists.
6. Store it sealed and dry, where children and pets cannot reach it. The general rules are in storing birdseed.
7. Keep it out of water. The labels say "Do not apply directly to water." Do not hang treated seed where it drops into a bird bath or a pond.

When it is worth using#

Pepper changes what a squirrel wants, not whether it can reach the feeder. That is why the site treats it as a top-up to correct placement, never a substitute. The geometry that actually keeps squirrels off is in baffles and poles, and the choice between a baffle and a squirrel-proof feeder is weighed in baffle vs squirrel-proof feeder.

For chipmunks, the practical answer is a feeder or tray that stops seed hitting the ground, set out in chipmunks. If you would rather change the seed than coat it, safflower is the other common way to make a feeder less interesting to squirrels.

What this answer does not cover#

The bird evidence is about pain, not every effect. In a 1983 study, capsaicin injected under the skin of red-winged blackbirds seemed to disrupt their temperature control in heat. It also stopped them telling warm water from cool. That was injection, not eating, but it shows capsaicin is not inert in a bird. We found no study of birds eating treated seed over a whole winter.

The field test was one spring, three yards near one town, gray squirrels and in-shell sunflower. It was a one-choice trial, so only one kind of seed was offered at a time. It did not test winter hunger, sunflower hearts or mixes, red or fox squirrels, or raccoons, deer, bears or rats. It says nothing about how long the coating lasts outdoors.

Pets are outside it too. The labels say only to keep the product from pets. If a dog has eaten seed from under the feeder, the wider risks are in dog ate bird seed, which does not rule on pepper-treated seed. Call your vet.

Frequently asked questions#

Does hot pepper bird seed hurt birds' eyes?

No study we found shows it does, and the biology says it should not. The receptor that makes capsaicin painful in mammals does not respond to it in birds, so they are indifferent to the burn. The eye warning on the bag is real, but read where it sits: under Hazards to humans and domestic animals. It is about you, your children and your pets. That warning is the main reason people assume the birds suffer too.

Does hot pepper bird seed keep chipmunks away?

No. The 1999 field test near Ithaca watched Eastern chipmunks at the same stations and found the treated seed was not effective in deterring them. Chipmunks are not on the label either: EPA had the registrant narrow it to gray, red and fox squirrels. To cut chipmunk visits, stop seed from reaching the ground, which is the approach set out in chipmunks.

Can I make hot pepper bird seed with cayenne from the kitchen?

You can, but you will not know the dose. A spice jar gives no capsaicin figure. The registered mix-in powder states 1.08% capsaicinoids, and its 1998 label mixes one part into 120 parts seed, which works out to about 89 ppm. Kitchen powder also makes dust, and dust is what reaches your eyes. If you do it, follow the same rules as the label: outdoors, out of the wind, in a sealed container, wearing gloves and eye protection.

Is hot pepper suet safe for woodpeckers and other birds?

The same receptor biology applies to every bird, so yes on the evidence available. The treated suet in the 1997 EPA records is 0.088% capsaicinoids, about 880 ppm, the hottest of the three forms as they go out. No field test covered suet, so how well it works on squirrels is untested. The handling rule is the same as for seed: rubber gloves, and do not touch your eyes or face until you have washed. More on cakes in suet for birds.

Why does hot pepper bird seed have an EPA number?

Because it is sold to drive animals away, and that makes it a pesticide under FIFRA, the federal pesticide law. EPA registered a treated seed, a treated suet and a mix-in concentrate in May 1997. The labels say it is a violation of federal law to use the product in a manner inconsistent with its labeling. EPA's notices also say registration is not an endorsement of the product.

Sources and further reading

1. Capsaicin-treated seed as a squirrel deterrent at birdfeeders (Curtis, Rowland, Curtis and Dunn, 9th Wildlife Damage Management Conference, 2000) University of Nebraska-Lincoln DigitalCommons Abstract and author list: 3 sites near Ithaca NY, 11 May to 24 June 1999; 40,000 SHU (2,424 ppm) shell, 2,000 SHU (121 ppm) heart; squirrel seed taken and feeding time significantly reduced; bird visits unaffected at 2 sites, up at 1; chipmunks not deterred; Dunn's affiliation
2. Notice of pesticide registration, EPA Reg. No. 68563-1, treated wild bird seed (20 May 1997) US Environmental Protection Agency 0.024% capsaicinoids; registered under FIFRA section 3(c)(5); addressed to Dr. Joseph A. Dunn; calm-day, glove and eye-protection directions; 'natural' claim struck
3. Notice of pesticide registration, EPA Reg. No. 68563-2, concentrate for treating bird feed (20 May 1997) US Environmental Protection Agency 1.08% capsaicinoids, mix 1 part to 40 parts feed (3 oz to 7.5 lb); 'Causes moderate eye irritation'; do not mix indoors or downwind; label limited to gray, red and fox squirrels
4. Revised label, EPA Reg. No. 68563-2 (stamped 19 November 1998) US Environmental Protection Agency Mixing ratio changed to 1 part to 120 parts feed (3 oz to 22.5 lb); store away from children and pets; do not apply directly to water
5. Notice of pesticide registration, EPA Reg. No. 68563-3, treated suet (20 May 1997) US Environmental Protection Agency 0.088% capsaicinoids from oleoresin of capsicum; gloves, avoid touching eyes and face until hands are washed
6. Molecular basis for species-specific sensitivity to "hot" chili peppers (Jordt and Julius, Cell 2002) PubMed Birds are indifferent to the pain-producing effects of capsaicin; the chicken vanilloid receptor is normally insensitive to it but responds to heat and acid
7. Directed deterrence by capsaicin in chilies (Tewksbury and Nabhan, Nature 2001) PubMed Capsaicin selectively discourages seed predators without deterring the more effective seed dispersers
8. Taxon-specific differences in responsiveness to capsaicin and several analogues (Mason, Bean, Shah and Clark, J Chem Ecol 1991) PubMed USDA APHIS Denver Wildlife Research Center: synthetic capsaicin not repellent to European starlings, best repellent of the compounds tested on Norway rats
9. Behavioral and physiological effects of capsaicin in red-winged blackbirds (Mason and Maruniak, Pharmacol Biochem Behav 1983) PubMed Injected capsaicin seemed to disrupt thermoregulation in heat and removed warm and cool water discrimination
10. 40 CFR 156.10, Labeling requirements eCFR, US Government Safety claims such as 'safe' or 'harmless', and 'Contains all natural ingredients', are examples of misbranding on a pesticide label