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It is thought that there are around 1200 native bird species in North America. But there are now also a staggering number of non-native bird species, around 100 at the last count!
You might think that diversity is a good thing, and in some instances, it is. However, when it comes to birds, too many non-native species can interfere with the ecosystem, spread disease, and use up valuable food sources that should be going to native birds.
What is an Invasive Species?
When we use the term invasive species, we are referring to non-native birds that enter a country or region and threaten the native population. But it doesn’t end there, these species can cause problems for humans as well, so sometimes it’s in our best interests to deter them.
There is a difference between a non-native bird and an invasive bird. In some cases, non-native birds may not be harmful and so would not be considered invasive.
You may be wondering how these birds even get into the region in the first place. Sometimes, this can happen through acts of humans, such as deliberately importing a species. Although nowadays, it’s more common that humans would accidentally import a species via freight carriers, for example.
Other times, the species can expand so much that there is a need for them to expand their range and will spread to new areas.
Non-Native Bird Species in North America
There are a startling number of non-native bird species in the USA. Some may be more common than others, but in most cases they may pose some kind of threat. We have detailed some of the non-native species that you may see in North America.
House Sparrow (Passer domesticus)
Sometimes you’ll hear these birds being called the English sparrow but whatever name they go by, these are incredibly invasive birds that have caused a real threat to the bluebird population. In fact, they are one of the main reasons for its decline.
House sparrows are native to Africa and Eurasia but were introduced to the States in the mid-1800s, with a mere 100 birds being released in Brooklyn, NY. They can now be found all over the USA and well up into Canada as well as in Mexico and parts of South America. The birds frequent all types of habitats, including farms, urban areas, and residential areas.
These birds are brown with black streaks, and this is the same with both males and females. Compared to the American sparrow, they’re a lot stockier and have shorter legs. They are small birds that don’t usually weigh more than 1 oz (28 grams).
European Starling (Sturnus vulgaris)
You may be surprised to learn that the European starling is now the most abundant bird in North America. It was first brought to the US by Eugene Schieffelin, a Shakespeare fan who wanted to add some of the Bard’s favorite birds to the country.
However, he didn’t really do the USA much of a favor since these birds pose a significant number of threats including up to $800 million worth of agricultural damage each year and the spread of avian diseases such as salmonella, blastomycosis, and transmissible gastroenteritis. European starlings are cavity nesters and will take over the nests of other birds. They also compete with several native species including the woodpecker and the bluebird.
There are more than 200 million starlings in the US and they can be found in all states. These birds prefer habitats close to humans so you’ll find them in gardens and urban areas. You will recognize them thanks to their yellow beaks and while they look black from afar, they actually have purple and green coloration. The birds are incredibly loud and tend to travel in groups.
House Finch (Haemorhous mexicanus)
House finches were only native to the western parts of the United States and Mexico. However, they were brought to the eastern states in the 1940s and it is now thought that there are around 30 million in this part of the country. But it is thought that numbers are starting to decline.
The male house finch has a bright red breast and face, while the female is largely brown with black markings. These small birds have a pleasant song, so many people don’t mind them being in the garden. While they do tend to compete with purple finches, they don’t pose a significant risk to most native avian life.
Shiny Cowbird (Molothrus bonariensis)
The male shiny cowbird has black/purple glossy feathers and is very attractive, while the female has a more brownish coloration. These birds are native to South America but have since moved north and now occupy some of the Caribbean nations as well as Florida.
They prefer fields, wooded streams, orchards, and gardens where there is partial coverage. The shiny cowbird is considered to be a low-level threat to native species. That said, it is a brood parasite and will lay its eggs in the nests of other birds before leaving to avoid raising its young. This is one of the biggest problems brought by the shiny cowbird.
Rock Pigeon (Columba livi)
Rock pigeons first came to North America with the English back in the 17th century. They are native to parts of Europe, Asia and down into Africa but there are now estimated to be more than 8 million rock pigeons in the USA, spanning all states, even in Alaska.
These birds are known to carry parasites which could be transmitted to native species, causing their decline. One of the most worrying things is that the rock pigeon is known to carry bird flu which again could cause a significant decline if transmitted to native birds.
The rock pigeon has mostly gray feathers with a bluish tinge to the head and black markings on the body. As their name suggests, they can be found in rocky or cliffed areas but are also a very common sight in urban spaces.
Eurasian Collared Dove (Streptopelia decaocto)
The Eurasian collared dove is native to parts of Europe and Asia and their natural habitat can spread as far and wide as Turkey to South Asia in countries like Sri Lanka. However, in the mid-70s, there was a burglary at a pet shop in the Bahamas and several of these birds were let loose.
It took until the 1980s for the Eurasian collared dove to reach Florida where they quickly began to populate the USA. They bred at an alarming rate and it is believed that there are around 400,000 in the wild today but they’re growing by as much as 37% per year!
These birds are gray in color with a crescent-shaped black marking around the back of the neck. For doves, they are a relatively large birds but so far, there doesn’t seem to have been any major impact on native bird life because of their presence. However, since these birds are new arrivals, it could take some time to properly see the effects.
Mute Swan (Cygnus olor)
The mute swan is native to Europe, particularly in Great Britain. The birds will migrate south to Africa in the winter but can now be found in North America thanks to their release here back in the 19th century. They were initially released in the northeastern states and largely remain here although there are some found as far west as Washington state.
Mute swans are large white aquatic birds with black markings around their face and an orange beak. They have a lot of cultural significance in the native countries and are considered to be decorative which is one of the reasons they were first brought here.
You will find mute swans in ponds and lakes but one of the biggest threats is the amount of submerged aquatic vegetation (SAV) they consume. While this might not be an issue if the swans ingested all of the aquatic vegetation they remove, they pull up far more than they actually eat. Removing this SAV reduces habitat and food for other aquatic life.
Muscovy Duck (Cairina moschata)
The muscovy duck can be found nesting in tree cavities and they prefer to live near water, typically in forests. These large birds can have a wingspan of up to 59-inches (150cm) and the males have distinct red markings on the face that almost look like warts. The females tend to have more blue coloration among the main black colors while the males have a white mark around the middle.
Muscovy ducks are native to South America and Mexico as well as in some parts of Texas. However, they can now be found in feral colonies across almost all of the USA and well up into Canada. The problem with this is that they are known to interbreed with native duck species and spread disease. They are considered an aggressive bird and will attack humans if they feel threatened.
Golden Pheasant (Chrysolophus pictus)
The first introduction of the golden pheasant was in 1990, and it was released into Hawaii. The bird appears to be thriving here, but there’s not enough evidence to suggest whether or not the bird is currently a threat. They are not typically found in other parts of the United States but have also been established in certain parts of the UK, despite being native to China.
The golden pheasant has a long tail which accounts for around a third of the overall length of the bird. It has a red body with a yellow crest as well as some blue coloring. However, this applies only to the males, whereas the females are mainly brown.
These birds are usually found at the edges of forests, and they like to nest in trees.
Ring-Neck Pheasant (Phasianus colchicus)
Ring neck pheasants are native to many parts of Asia including as far east as Korea and as far west as the Black Sea. These birds pose a threat to native ground-nesting birds in the USA since they are known to attack them. It is not uncommon for the females to lay their eggs in the nests of birds such as gray partridges and greater prairie chickens.
The ring-neck pheasant is a large bird with colorful plumage including coppery colors and blue around the head. However, the females are mainly brown in color. They prefer agricultural land and fields and can be found across many of the Northern and Eastern states.
These birds were originally introduced as far back as the 1700s but it wasn’t really until the late 1800s that they really settled in the country.
Red-Whiskered Bulbul (Pycnonotus jocosus)
While the red-whiskered bulbul is not native to the USA, it appears that it is not currently a serious threat to our native species.
These birds are actually native to India but were introduced into the United States by accident in 1960 after several birds escaped from an aviary in Miami, Florida. Since the birds enjoy a tropical setting with lots of trees and berries, this was the perfect location for them and they seem to have thrived here.
The red-whiskered bulbul has a brown body with a white breast and a very distinctive black and red head and face. While they are usually found in forests, it is not uncommon to see them in backyards in Florida as well as in Hawaii where there was another accidental release.
Quaker Monk Parakeet (Myiopsitta monachus)
Monk parakeets are native to South America but have established wild colonies in North America due to escaped birds from the pet trade since the 60s. They can now be found in abundance in Texas and Florida. There have been confirmed sightings in Rhode Island, Delaware, Oregon, and Illinois.
One of the main issues with these birds is that they are eating grains and crops which is having a serious impact on the agricultural industry. They’re known for eating the seeds and saplings of certain native plants which stops them from becoming mature.
You’ll easily be able to spot the monk parakeet thanks to its green plumage and small hooked bill. The males and females have a grayish/white breast and face and the birds can typically be found in woods but mainly in urban areas.
Rose-Ringed Parrot (Psittacula krameri)
The rose-ringed parrot is found natively in Asia and Africa but since they have long been kept as pets, there have been many escaped birds that have gone on to colonize cities all around the world. In North America, there are established colonies in Florida and California.
The rose-ringed parakeet is a very distinct-looking bird with bright green feathers and a black ring around the neck. In the USA, you’ll usually find them in urban areas but they do enjoy forests, deserts, savannahs, and a whole host of other habitats in their native environments.
Much like the monk parakeet, the rose-ringed parrot poses a threat to agriculture by feeding on crops. There is also some concern about the birds spreading diseases and a notable number of collisions that interfere with humans such as those with aircraft.
Cattle Egret (Bubulcus ibis)
The cattle egret could be considered to be a colonizer since it was not introduced to North America but rather made its own way here. Native to Africa, the cattle egret has been found in America since the early 40s and is largely found in the Southern parts of the United States.
These large white birds with bright orange beaks don’t pose as much of a threat to native birds if any at all. In fact, they are known for eating ticks and flies around livestock so could be considered beneficial to this industry.
How Does Invasive Species Threaten Bird Biodiversity?
US authorities are attempting to control the population of non-native species and they are trying to do this in the most humane way possible. Some of the methods include destroying nests and trapping the birds, as well as targeted poisoning. The problem is that there are still a significant and alarming number of non-native bird species in North America that are causing some worrying problems.
When we think about these problems, we usually associate them with the effects on our native bird species. While there is a very obvious impact on native birds, we also have to consider that these effects spread to the wider ecosystem.
For example, non-native species will compete with native birds for food but they will also feed on farmer’s crops which puts a direct strain on the agricultural industry. For some native species, it’s almost impossible to compete and as such, there have been significant declines in their population with the bluebird being one of the most seriously affected.
Non-native bird species are fighting with our native birds for nesting spots so it is becoming more difficult for North American birds to safely and successfully breed. On top of that, there are a lot of brood parasites that are laying non-native eggs in native nests and leaving the birds to raise their young.
There are lots of non-native birds, such as rock pigeons, that are known for carrying diseases which, when spread to our native species, will again cause a decline in numbers.
There are problems with some non-native birds attacking other species which is something that has been seen between house sparrows and bluebirds; another reason that there has been a serious decline in the population of these native birds.
How to Discourage Invasive Birds from Visiting Your Yard
While American authorities are doing their bit to discourage non-native bird species, the responsibility falls on all of us. There are things you can do to deter non-native species when you see them in your garden. Some of the most common non-native avian species are the house sparrow, European starling, and the house finch.
Bird Scare Devices
There is a range of scare devices on the market that are harmless to birds but will emit noise or use visual stimuli to scare the birds away. There are things such as scary-eye balloons and pretend predators that work particularly well.
However, do keep in mind that the birds may become accustomed to seeing these devices so it is essential that you vary their placement.
One of the most effective ways to deter birds from your garden is to simply exclude them by preventing them from entering.
Things such as spikes along fence tops are particularly useful as well as installing angled boards along walls. You may also consider placing netting over areas that non-native bird species may use for nesting.
While you may wish to have bird baths and feeders for native species, you should consider making these difficult for non-native birds to use. One way to do this is to make sure that water in bird baths is at least six inches below the rim as this will make it difficult for starlings to access the water; they’ll usually give up and go elsewhere.
Starlings will also find it tricky to get through wire wrapped around bird feeders, so this is also a great exclusion technique. You should also consider what types of food you put into your feeders. If starlings are a problem then using things like peanuts or nyjer seeds will largely deter them as these foods are not part of their preferred diet.
Modifying their Habitats
It is important to try to make the habitat in your garden as unfavorable as possible to non-native birds. You can do this by ensuring that no food or water is left out; even something as seemingly innocent as a pool left over from an air-con system could attract birds.
Since birds enjoy a lot of tree cover, removing this will act as a deterrent. That doesn’t mean that you cannot have trees or shrubs in your yard but just be sure to stay on top of pruning them.
Where it is not possible to prune or cut down a tree, you can use covers such as agricultural fleeces or plastic to prevent birds from nesting during nesting season. If you find that you have problems with birds entering the home to nest then take the time to seal any openings to remove this issue.
If you do happen to find the nest of a non-native bird in your garden then you should remove it. Note that there are laws preventing you from interfering with native birds’ nests so make sure you are 100% certain of what you’re dealing with before removing anything.
Is it Legal to Move the Nest of an Invasive Bird Species?
In the USA, it is largely illegal to disturb or remove a bird’s nest. However, when it comes to invasive species, these birds are offered no protection. This means that you can legally remove their nest without any ramifications for yourself.
Are Invasive Bird Species Protected by the Migratory Bird Treaty Act?
The Migratory Bird Treaty Act (MBTA) protects native birds from humans and has been in force since 1918. It has become so effective that other countries have joined forces with the USA to uphold their own treaties for the protection of birds. However, in this country, only native species are protected under this law. The following non-native birds are not covered by the MBTA:
- European starling
- House sparrow
- Rock pigeon
- Muscovy duck
- Eurasian collared dove
- Mute swan
- Chinese goose
- Ring necked pheasant