Wait, There Are Poisonous Birds?

ByEllen Rigell Earth.com staff writer

While not very common, there are a handful of poisonous birds! Though we wouldn’t be too worried next time you see a flock passing overhead. Many of these birds live discreet and elusive lives. Some have been dangerous to humans in the past, but thanks to modern science, we know quite a bit more about what is safe to put on our plate. Here we have our ranking of the most poisonous birds. Learn how these feathered fiends get their toxins and read to the end to find out the most dangerous poisonous bird!

Poison vs. Venom 

Before we dive into the details around these fascinating birds, let’s review some key vocab words. While both poisonous and venomous animals use toxins as a defense strategy, they have a distinct difference. Venoms require an injection through a bite or sting (viperous snakes, wasps, spiders…). On the other hand, poisons are transferred through more passive contact like touching or eating (poison ivy, monarch butterfly, poison-dart frogs).

How Do Birds Become Poisonous?

Animals can develop toxins in a few different ways. Some can produce their own toxins and have a specific gland or organ for secretion. Others adapt and integrate poisons from other organisms. In most cases, they will consume and repurpose a toxin that will be distributed throughout their tissue rather than restricted to a specific gland. While many insects and amphibians develop their own toxins to deter predators, most poisonous birds integrate toxins from their diets. 

This strategy is called heteroaglandular poison. The prefix “hetero” refers to getting the chemical defense from another source, and “aglandular” means that there isn’t a specific organ or gland that houses it. By eating other poisonous plants or animals, some bird species  

Do They Poison Themselves?

How do they not poison themselves, you might ask? Poisonous birds, such as the hooded pitohui, often have a specific protein that soaks up the toxins before they can harm the animal itself. Called “toxic sponges,” these protect the birds from any toxic effects while allowing the poison to remain in their feather, skin, or tissue.

Ranking of Poisonous Birds

While only studied in the past few decades, poisonous birds have evolved around the world. Examples of toxic birds have shown up across avian taxa, indicating convergent evolution. This means that poisonous birds aren’t all in the same genus or even family. Several different lineages of birds have developed a chemical defense system independently. From passerine songbirds to large game fowl, below are some of the most common poisonous bird species. Additionally, we’ve ranked them from most dangerous to least dangerous, so you know what to watch out for!

Rare and Wiley: The Red Warbler

The red warbler (Cardellina rubra) keeps to itself in the Mexican highlands. For a long time, the little bird has been nondescript apart from its beautiful plumage and elusiveness, but the ancient Aztec knew better. Similar to how the indigenous Guinean people avoided the pitohui birds, the Aztec had recorded a small red bird as being inedible.  To test this theory, scientists injected extracts from the red warbler’s feathers into study mice. The mice were immediately agitated, alternating between acting hyperactive and inactive. 

The Poison

The toxin appears to include a mix of two different alkaloids. However, more research needs to be done to identify the specific chemicals. Since the warbler is completely insectivorous, the poison likely comes from a toxic bug in its diet.

The Hooded Pitohui

Passerine Poisons: The Hooded Pitohui

Native to the Papua New Guinea rainforest, the hooded pitohui (Pitohui dichrous) was one of the first poisonous birds to be discovered. Pitohui birds are a lovely rusty orange with bold black feathers on the head, wings, and tail. Their specific toxin comes from their diet. The birds eat poisonous Choresine beetles – the same insect that gives some poison dart frogs their toxicity. The native people of Papua New Guinea have nicknamed the pitohui the “rubbish bird” since it’s a bad option for dinner. 

The Poison

The steroidal alkaloid called homobatrachotoxin is found in the pitohui’s feathers and skin. Since the poison is most highly concentrated on the feathers, it’s likely meant to be a deterrent for parasites like lice and ticks.

Fun Fact: When discovering the poison on the pitohui, researcher Jack Dumbacher made the realization when his hand burned after untangling this dove-sized bird from a mist net in 1988. He also tested his theory by putting a clipping of a feather in his mouth! That’s some scientific sacrifice!

The Unsuspecting Poisonous Bird: the Little Shrike-Thrush

Another little Australian songbird, the little shrike-thrush (Colluricincla megarhyncha) garnered the attention of bird toxicity studies along with the pitohui. However, only a couple of specimens have been found to be poisonous. Since this is not a species-wide phenomenon, this further advances the theory that the poison is diet-based. The shrike-thrush only becomes poisonous when it eats certain food.

The Poison

The chemical batrachotoxin again is the culprit, likely from the same insect or plant food source that the pitohui eats.

Bronzewing Pigeon

Poison to Protect: The Bronzewing Pigeons

The bronzewing pigeon’s (Phaps spp.) toxicity is a bit of a superpower. Living in southwest Australia this little bird acts as the spokesperson for its native ecosystem. As we’ve seen time and time again, when humans introduce a nonnative predator into a habitat, they often cause problems for the native community. Our domesticated cats and dogs are often the culprits, and, in many cases, they are a factor in animal extinction (e.g. the dodo bird).  However, cats and dogs beware because the bronzewing pigeon has a defense! Like many animals in its habitat, it feasts on the tasty plant GastrolobiumThough an important part of the diet for these poisonous birds, the plant harbors a chemical that is fatal to anyone else. 

The Poison

The poison fluoroacetate acts as an inhibitor for cellular respiration, causing a range of responses from intense stomach pain to death.

Ruffed Grouse

Risky in Winter: Ruffed Grouse

Hunters and birders from North America will be surprised to see the ruffed grouse or partridge, (Bonasa umbellus) on this list. In fact, many fowl hunters often serve grouse at the dinner table. In the 18th and 19th centuries, however, reports of grouse poisoning surfaced across the country. When observed by a physician, consumers experienced nausea, vomiting, and vision impairment. But what was causing this and why is it not a problem today?

The Poison

The dominant theory behind the ruffed grouse poisoning is, unsurprisingly, in its diet. In the winter, the grouse often forages on mountain laurel buds which contain the chemicals andromedotoxin and arbutin. Toxic to mammals, they don’t seem to affect the grouse. Today no one succumbs to grouse poisoning due to the current hunting regulations. Since the grouse can not be shot in the winter or spring, hunters avoid the time of year when the poisonous birds are at their most dangerous. 

Spur-winged goose

The Most Intimidating Poisonous Bird: Spur-Winged Goose

A strange bird from the start, the spur-winged goose (Plectropterus g. gambensis) makes an impression. These large birds can weigh up to 20 pounds and are highly aggressive. Not only will they fiercely defend their territory, but they also have the weapons to do it. Each goose has a sharp spur on the end of each wrist that they wield against invaders. While all spur-winged geese are rather intimidating, only one population of the geese is actually poisonous. In the Gambia, the geese tend to eat the poisonous blister beetle. However, while they are immune to the toxin, their flesh is imbued with it. 

The Poison

Integrating the chemical from the blister beetle, the toxin in question is the terpenoid compound called cantharidin. 

The common quail, looking completely unsuspecting.

The Most Dangerous Poisonous Bird: The Common Quail

The common quail (Coturnix commix coturnix L.) easily makes it toward the top of the list of poisonous birds. Though it looks more like a fluffy football than a toxic menace, we wouldn’t recommend serving this particular quail for dinner.  Also called the European quail, this particular fowl has likely affected the most people. In fact, the danger of quail poisoning has reached such heights to warrant its own name – coturnism. Similar to the ruffed grouse, the quail picks up the poison from its diet, but only seasonally. Depending on the location, quail are only dangerous during the spring or fall migration. Other times of the year, the birds are completely safe to eat.

The Poison

While there has been some debate as to the origin of the poison, current theories suggest the quail eat the toxic seeds from the mint plant Slachys annua. Sickness from coturnism can result in weakness and muscle pain to paralysis along with vomiting, kidney failure, cardiac arrest, and even death. 

Happenstance or Defense?

While some poisonous birds, like the bronzewing, seem to have advantageously evolved to incorporate toxins, others, like the goose, seem a bit more random. However, all the species likely benefit from their poisons. Nobody wants to eat a toxic bird, and their potential predators learn pretty quickly that a birdy bite can make them sick.