10 INVASIVE Animals found in Illinois! (2024)

What kinds of invasive species can you find in Illinois?

Animals that are not native can cause many problems. They put a lot of pressure on native species as they compete for food, territories, and nesting areas.

Below, you will learn about an array of different invasive creatures, along with the myriad of problems they cause!

10 Invasive Animals Found in Illinois:

Just a quick note: you won’t find any insects or fish below. Those articles are coming soon! 🙂


#1. Rock Pigeon

  • Columba livia

Types of invasive animals in Illinois

These invasive birds are common in Illinois but are almost exclusively found in urban areas. Rock Pigeons are what everyone refers to as “pigeons.” You have probably seen them gathering in huge flocks in city parks, hoping to get tossed some birdseed or leftover food.

The typical pigeon has a gray back, a blue-gray head, and two black wing bars. In addition, look for a green and purple iridescence around their necks!

Rock Pigeon Range Map

pigeon range map

Love them or hate them, Rock Pigeons have been associated with humans for a long time! Some Egyptian hieroglyphics suggest that people started domesticating them over 5,000 years ago. But, interestingly, scientists aren’t even sure where their original range occurs!


#2. Domestic Cat

  • Felis catus

Types of invasive animals in Illinois

  • Can be a wide range of colors, sizes, shapes, and fur lengths.
  • Selected mutations observed in many pet cats, such as folded ears, munchkin legs, or flattened faces, are not commonly seen among domestic cats successfully living feral.

Sadly, domestic cats are very damaging to the ecosystems in Illinois where they are introduced. It has only been in the last century or so that cats have become pets that stay indoors.

It is estimated that these invasive animals kill over 1 billion birds and 6 billion other small animals annually. Feral cats that live and breed away from the care of humans are the most prolific hunters.

As you can imagine, this issue is hotly debated due to the love people have for their pet cats. Some experts think that trap-neuter-return programs are key to curbing the problem of feral cats. At the same time, others are huge proponents of NEVER letting your cat outside.


#3. European Starling

  • Sturnus vulgaris

Types of invasive animals in Illinois

  • They are about the size of an American Robin. Their plumage is black and appears to be shiny.
  • Breeding adults are darker black and have a green-purple tint.
  • In winter, starlings lose their glossiness, their beaks become darker, and they develop white spots over their bodies.

Despite being common, European Starlings are an invasive species in Illinois.

Back in 1890, one hundred starlings were brought over from Europe and released in New York City’s Central Park. The man responsible (Eugene Schieffelin) had a mission to introduce all of the birds mentioned in Shakespeare’s plays to North America.

European Starling Range Map

starling range map

The rest is history as starlings easily conquered the continent, along the way out-competing many of our beautiful native birds. Their ability to adapt to human development and eat almost anything is uncanny to virtually no other species.

Here’s something amazing about these non-native birds:

It’s the magical way they travel in flocks, called murmurations. Check out the video below because it’s mesmerizing. 🙂

YouTube video

#4. Eurasian Collared-Dove

  • Streptopelia decaocto

Types of Invasive Species in Illinois

  • A mostly sandy gray bird with a long, square-tipped tail.
  • As the name suggests, look for a black collar on the back of the neck.

Interestingly, these birds are invasive to Illinois.

Unfortunately, somebody introduced Eurasian Collared-Doves to the Bahamas in the 1970s, and since then, they have rapidly spread. In fact, their population is still spreading!

Eurasian Collared-Dove Range Map

Eurasian collared dove range map

One of the reasons these birds colonized here so quickly is due to their comfort level with humans. They have thrived being around bird feeders and in urban and suburban areas. It’s common to see them on the ground or platform feeders eating grains and seeds.

How do you tell them apart from Mourning Doves?

At first glance, Eurasian Collared-Doves look very similar to the native Mourning Dove. Here’s how to tell them apart:

Types of Invasive Species in Illinois

  • Mourning Doves are smaller and have black dots on their wings.
  • Eurasian Collared-Doves are larger and have a black crescent around their neck.

#5. Mute Swan

  • Cygnus olor

Types of Invasive Species in Illinois

  • A huge white bird with a long white neck.
  • Look for the distinctive orange bill that features a black base and knob.

Mute Swans are among the most elegant and beautiful birds you will see in the water. They are also enormous and are one of the heaviest birds that can fly!

But did you know that Mute Swans are NOT native to Illinois?

Due to their beauty, Mute Swans were imported from Europe and released in parks, large estates, and zoos. Unfortunately, these individuals escaped and have established an invasive wild population.

Don’t be fooled by their appearance; these invasive animals can be aggressive and regularly attack kayakers and other people who get too close to their nest. They also displace native ecosystems due to their voracious appetite, which requires up to 8 pounds (3.6 kg) of aquatic vegetation daily!

Despite their name, these swans are not mute!

While relatively quiet, they make a hoarse trumpet sound when defending their territory. And if they are threatened, expect to hear various barks, hisses, and snorts.


#6. House Sparrow

  • Passer domesticus

house sparrow

House Sparrows are an invasive species that originated from the Middle East. But now they are one of the most widespread birds in Illinois (and the world)!

House Sparrows owe their success to their ability to adapt and live near humans. Because of this, they are almost always found in urban and suburban areas.

Range Map – House Sparrow

house sparrow range map

House Sparrows can be heard across the entire planet. Pay attention the next time you’re watching the news in another country. Listen for a simple song that includes lots of “cheep” notes.

YouTube video

#7. House Mouse

  • Mus musculus

House Mouse

  • The tails are hairless and can be as long as their bodies.
  • House Mice are smaller and lighter built than rats.
  • They usually have light brown fur and large round ears compared to their heads, which give them a cute look.

These invasive rodents originated in Asia but can now be found in Illinois. House Mice arrived in North America on ships in the 1600s and quickly multiplied.

Mice have dispersed across the planet incredibly successfully, second perhaps only to humans. The biggest key to their success is their ability to adapt their behavior quickly and breed prolifically.

House Mouse Range Map

Native range (dark red). Introduced (light red) Attribution: Osado, Public domain, via Wikimedia Commons
Native range (dark red). Introduced (light red) Attribution: Osado, Public domain, via Wikimedia Commons

Salmonella and parasites are the most prevalent illnesses that mice transmit to humans by contaminating food. However, this risk has been greatly reduced through modern food management techniques in the USA.

House Mice also greatly impact the ecosystems that they invade. They are omnivorous and will devour plants and target animal species that have not adapted to fighting them off.

Fascinatingly, House Mice also cause the decline of native species by bolstering the health of predators through seasons when other prey would have been hard to find. By becoming prey themselves, the mice inflate the populations of predators year-round.


#8. Greylag Goose

  • Anser anser

  • Greylag Geese are a soft, warm gray-brown.
  • Their feathers are rimmed with narrow white edges, which gives them a delicate barred pattern over their wings, chest, and sides.
  • The legs are pink, while their bills are bright orange.

Greylag Geese are NOT native to Illinois!

These birds are found naturally across Europe and Asia, where they are very common and have a huge natural range.

Interestingly, Greylag Geese gave rise to almost all common domesticated goose breeds.

Domesticated Greylag Geese can commonly be seen on farms, estates, and in zoological collections. But, occasionally, escaped birds may flourish as feral populations.

Greylag Geese are very social animals. They will almost always be found in flocks, ranging from a few birds to thousands of animals. When flying, flocks adopt the classic V-shape flight formation. Play the video to see them in action!

YouTube video

#9. Ring-necked Pheasant

  • Phasianus colchicus

  • Males have tawny bodies, shiny green heads with red wattles, and a white ring at the base of the neck.
  • Females are smaller and are tawny brown all over, with dark brown patterning.
  • Both have extended tail feathers, though males are longer.

Ring-necked pheasants are eye-catching birds that are native to Asia. They are usually found in woodlands and grasslands.

These birds were intentionally imported and introduced to the USA in 1881. In fact, they have been here so long that most people have no idea that Ring-necked Pheasants are not native to Illinois!

Ring-necked Pheasant Native and Introduced Range Map

Native range (purple). Introduced range (pink). Attribution: Cephas, CC BY-SA 4.0, via Wikimedia Commons

Ring-necked Pheasants cause issues for native ecosystems in several ways. First, their breeding success and population growth put a strain on habitat and food availability. Ring-necked Pheasants outcompete native birds for limited resources. Pheasants can even be openly aggressive towards other birds.

Second, the breeding behavior of Ring-necked pheasants leads to them parasitizing nests, directly causing the mortality of native hatchlings. Pheasants nest on the ground, close to other species. Sometimes, they lay their eggs in the nests of other birds.


#10. Monk Parakeet

  • Myiopsitta monachus

Monk parakeet

  • Males and females look almost identical, though females tend to be a little smaller.
  • Bright green plumage with blue wing tips.
  • Large orange beaks and paler chests.

Monk Parakeets are a species of parrot originating in South America. Their ability to mimic sounds and words, combined with their social nature and beautiful plumage, has made them popular pets around the globe.

In the 1950s and 1960s, thousands of Monk Parakeets were imported as exotic pets for sale in the USA. Many of them escaped or were intentionally released over time.

These invasive birds build prolific nests in Illinois.

Their nest-building has caused direct conflict with humans by damaging homes and buildings. They are gregarious birds and often build huge, chambered nests that house multiple families.

YouTube video

For warmth, they have taken to building these incredible nests around heating elements, such as on electrical pylons and power stations.

This behavior has caused many issues for the people who rely on the electrical grid and the companies that maintain them. The nests can short-circuit the electrical facility, become a fire hazard, and damage equipment. Removing the nests is a very dangerous job and a temporary fix as the parakeets quickly rebuild.

Monk Parakeets do not seem to have a strong negative impact on native fauna. They may increase competition for food and can become agricultural pests when they feed on fruit crops. However, their prolific nest-building behavior actually leads them to act as ecosystem engineers and potentially increase nesting opportunities for other bird species. They feed and nest alongside native birds with little conflict (Cristóbal Briceño et al.)


Learn more about other animals in Illinois!


Which of these invasive species have you seen in Illinois?

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