The United States is home to over 900 bird species, making it one of the most diverse countries in the world when it comes to avian life. However, not all of these birds originated in North America. Many were introduced through human activities over the past few centuries. Understanding which birds are native and non-native to the US can help inform conservation efforts and preserve natural ecosystems.
What does “native” mean for birds in the US?
A native bird species is one that occurred naturally in a region without being introduced by humans. For birds in the United States, native species are those that historically bred and lived in North America prior to European settlement in the 1500s. Birds that expanded their ranges and arrived in new areas without human assistance are still considered native.
There are several ways to determine if a bird is native or non-native to the United States:
- Fossil record – Archaeological and paleontological evidence can show if a species existed historically.
- Early ornithological accounts – Writings from naturalists and early explorers can document species occurrences before widespread human alteration of habitats.
- Habitat suitability – If a habitat exists that meets all of a species’ survival needs, it is more likely to be native.
Species that do not meet these criteria, but currently live and breed in the US, can be considered non-native or introduced. Many non-native species were purposefully or accidentally brought to North America through trade, migration, farming, hunting, and other human activities.
Why does native status matter?
Understanding native status helps identify effects of introduced species and manage vulnerable ecosystems. Non-native species that thrive and spread aggressively can negatively impact native species through:
- Competition – Non-natives may compete for limited resources.
- Predation – Introduced predators can deplete native prey.
- Habitat alteration – Newcomers can change habitat conditions.
- Disease introduction – Non-native birds may carry new pathogens.
These pressures from invasive species are one of the leading causes of native bird declines and extinctions. Conservation efforts prioritize protections for vulnerable native species being impacted by aggressive newcomers. Knowing the origin of birds also helps manage ecosystems in their historic state before human intervention.
Examples of common non-native birds in the US
Many non-native birds are now widespread and well-known across North America. Some examples include:
Rock Pigeon
Rock pigeons, commonly seen in urban areas, were originally native to Europe, Asia, and Africa. Escaped domesticated carrier pigeons led to the development of wild urban flocks across North America.
European Starling
European starlings were intentionally introduced to New York’s Central Park in the 1890s. Populations rapidly spread across North America. Their aggressive behavior often displaces native cavity-nesting birds.
House Sparrow
Also called the English sparrow, house sparrows came from Europe and were introduced to New York in the 1850s. They are now abundant across North America, often dominating bird feeders.
Eurasian Collared-Dove
Originally from Asia, Eurasian collared-doves escaped captivity in the Bahamas in the 1970s. They rapidly expanded their range across the US, competing with native mourning doves.
Major categories of non-native birds
Introduced birds can be grouped based on how they arrived and established in North America:
Escaped cages and collections
The pet trade and menageries brought many exotic species to America. Escaped birds founded some populations, including:
- Monk parakeets from South America
- Red-crowned parrots from tropical Asia
- Ring-necked pheasants from Asia
Purposeful introductions
Some non-natives were intentionally released, often for hunting, erratically considered environmental benefits, or nostalgia. These releases established:
- Ring-necked pheasant from Asia
- Gray partridge from Europe/Asia
- Chukar partridge from Eurasia
- Wild turkey from Mexico
Stowaways on ships
Birds sometimes traveled to North America unintentionally on boats and ships. Common examples are:
- House sparrow from Europe
- European starling from Europe
- Cattle egret from Africa
Natural range expansions
Some non-native birds expanded into the US naturally without direct human assistance. These include:
- Eurasian collared-dove from the Bahamas
- Great-tailed grackle from Central and South America
Regions with the most non-native bird species
States bordering the ocean and those in the southern US tend to have more established introduced species. Regions with the most non-native species include:
- Florida – Over 50 established non-native species, including many parrots, mynas, and bulbuls
- California – Over 30 species, including parakeets, pheasants, and Eurasian birds once caged
- Pacific Northwest – Over 30 species, including European starlings, Eurasian skylarks, and bullfinches
- Northeastern states – Over 25 species, including house sparrows, European starlings, and Eurasian tree sparrows
The diversity of non-natives declines further inland and in northern states. Hawaii also has many introduced bird species across its islands.
Notable extinction threats from non-native birds
Some vulnerable native US birds threatened by aggressive newcomers include:
- Hawaiian duck – Endangered by disease, habitat loss, and mallard hybridization
- Florida scrub-jay – Pushed out of habitat by shining cowbirds
- Red-cockaded woodpecker – Nest cavities often overtaken by house sparrows
- Golden-cheeked warbler – Competes with European starlings for nest sites
- Kirtland’s warbler – Brown-headed cowbird brood parasitism reduced reproduction
Careful conservation management helps protect habitats and control problematic non-native species where they pose extinction risks.
Non-native bird management and policies
Several approaches help reduce impacts of disruptive introduced birds, including:
- Prevention – Restricting import and interstate transport of high-risk species
- Population control – Humane culling, contraceptives, relocation, etc.
- Habitat management – Ensuring adequate habitat for native species
- Monitoring – Tracking population trends of native and non-native species
The Migratory Bird Treaty Act and Lacey Act provide legal protections limiting trade and spread of non-native birds identified as threats. Ongoing research, planning, and policy aim to find an appropriate balance between control/eradication efforts and humane coexistence strategies for established non-natives.
The future of non-native birds in North America
Ongoing human transportation networks and climate change will likely increase rates of accidental and intentional bird introductions. Novel diseases, shifting ranges, and extreme weather events will also influence community structures.
Careful management can limit future risks. However, modeling studies suggest at least 50-75 non-native breeding bird species may become established in North America by 2050. Ongoing monitoring, impact reduction protocols, and habitat conservation will be necessary to support native biodiversity.
Conclusion
North America’s diverse introduced bird fauna is linked to the continent’s history of global trade, agriculture, and wildlife exploitation. While many non-natives cause no measurable harm, problematic aggressive species can negatively impact native birds through competition, predation, brood parasitism, habitat alteration, and disease transmission. Careful policies, monitoring, humane population control, and habitat conservation can reduce ongoing threats to native species. However, climate change and globalization will likely lead to more introductions, requiring proactive management of vulnerable ecosystems.