The United States is home to a remarkably diverse population of bird species. With varied landscapes ranging from tropical to arctic, mountainous to coastal, and dense forests to open prairies, the country provides habitats for both permanent residents and migratory birds that breed during the warmer months. But exactly how many different species of birds live in or pass through the US?
Quick Answer
There are approximately 900 species of birds that have been documented in the United States and its surrounding waters as permanent residents, summer or winter visitors, or rare vagrants according to the official list maintained by the American Ornithological Society (AOS). This number represents nearly 1/3 of all the bird species in the world. With new species still being discovered around the globe, and the potential for vagrancy, the list of American species continues to grow each year.
Detailed Answer
As of 2023, the AOS Checklist of North and Middle American Birds includes 905 species that have been verified with physical evidence in the continental US, Alaska, Hawaii, or surrounding oceans. This checklist is considered the authoritative source on the status of birds across the United States and is updated annually as new species gain recognition and others are reclassified or removed based on new evidence.
The species on the AOS Checklist can be grouped into the following categories:
Permanent Residents
Roughly 390 species nest in the US and are present year-round in at least part of their range. Species like the Bald Eagle and American Robin maintain territories and breed here annually. Other examples include wild turkeys, chickadees, woodpeckers, and common backyard birds. Resident species may only inhabit certain regions or specialized habitats within the US.
Summer/Warm Climate Visitors
Around 150 species come to the US to breed during the warm summer months, migrating south to their wintering grounds in Latin America, the Caribbean, or the southern US during the colder months. Examples include colorful neotropical songbirds like warblers, tanagers, orioles, and buntings. Terns, sandpipers, and plovers also arrive to nest at coastal and inland wetlands in the summer.
Winter/Cold Climate Visitors
Over 75 species migrate from the northern latitudes and Canada to overwinter in the relatively milder climates found across the southern and coastal US. Prime examples include ducks, geese, swans, loons and some gulls. Snowy owls, juncos, and robins also spend winters in the US after breeding farther north.
Passage Migrants
Around 275 species pass through the US during their epic migrations between summer breeding and wintering grounds elsewhere. They use key stopover habitats to rest and refuel. Well known migratory species include hawks, shorebirds, and the monarch butterfly. Areas like Cape May, New Jersey witness remarkable concentrations of migrating birds.
Pelagic Species
The US includes vast marine territories stretching from the Caribbean to the Pacific, where 85 species of pelagic seabirds like albatrosses, petrels, and shearwaters may occur, in addition to birds that live in coastal areas. Many are migrants that disperse widely across the oceans after breeding.
Vagrant Visitors
Rare unforeseen weather events or navigation errors can deposit individual birds in areas far from their normal range. These vagrants account for around 20 species recorded in the US. Examples include Europe’s common cuckoo and northern wheatear. Vagrants provide exciting surprises for birdwatchers.
Individual States
While approximately 900 species of birds have been recorded across the entirety of the US, the number documented in each individual state varies based on size, geographic location, and habitats present. Here are some state highlights:
- California: Approximately 550 species, the most of any state, aided by diverse terrain and a long coastline.
- Texas: Around 650 species, second only to California in diversity, including many southern and migratory species.
- Florida: More than 500 species identified, including tropical species not seen elsewhere in the continental US.
- New York: Approximately 450 species, including migrants along major routes like the Atlantic Flyway.
- Alaska: Around 450 species as well, including Asian vagrants across the Bering Sea.
- Hawaii: Roughly 150 endemic species, including many rare forest birds.
Changes Over Time
The number of recognized bird species in the US has increased over decades as new species are described by science and taxonomic organizations like the AOS update their classifications. Some examples:
- In the 19th century, early naturalist pioneers like John J. Audubon documented North American birds, laying the groundwork for contemporary taxonomy.
- Roger Tory Peterson’s seminal 1934 Field Guide to the Birds helped popularize birdwatching and supported new discoveries.
- In 1983, the AOS North American Classification Committee was formed to evaluate bird taxonomy, splitting and lumping species based on new research.
- The number of documented US species grew from around 800 in the 1960s to nearly 1,150 by the early 2000s as taxonomic changes were implemented.
- Following extensive taxonomic revisions in recent years, the number recognized by the AOS stabilized around 900-920 species.
Ongoing research and analysis will likely continue to mildly adjust this number as species definitions are refined. The possibility of new vagrants also remains compelling. But the AOS list provides the most authoritative answer available to the question of how many bird species inhabit the diverse ecosystems of the United States.
Global Context
The approximately 900 species verified in the United States account for about 30% of the roughly 10,000 known living species of birds worldwide. Parts of Latin America and Asia surpass the United States in total diversity, but the country holds more species than any other nation comparable in size and geographic span. Factors contributing to the US having such a high count include:
- Diverse geographic regions spanning subtropical to subarctic zones.
- Coastlines along the Atlantic, Pacific, Gulf of Mexico, and Arctic oceans.
- Habitats ranging from tundra to prairies, forests, wetlands, mountains, and deserts.
- Position within major North American flyways for migrating species.
- Proximity to eastern and western hemisphere groups of bird species.
For its size, the United States provides an abundance of environments for both resident and migratory birds. The tally of approximately 900 species reflects this diversity and richness, explaining how birdlife here accounts for close to 1/3 of the planet’s known avian diversity.
Category | Number of Species |
---|---|
Permanent Residents | 390 species |
Summer Visitors | 150 species |
Winter Visitors | 75 species |
Passage Migrants | 275 species |
Pelagic Species | 85 species |
Vagrant Visitors | 20 species |
This table summarizes the approximate numbers of birds by migratory status that combine to make the total of 900 species recorded in the US.
Conclusion
Bird diversity in the United States is exceptional, with approximately 900 species verified across the country and surrounding waters. Species counts are highest in states like California and Texas that span multiple geographic regions. The number of documented species has grown over time thanks to continuing taxonomic research and discoveries. But the tally has now stabilized around 900, representing nearly a third of the planet’s known bird diversity. For any bird lover, the United States offers an abundance of avian life to appreciate through recreation, research, conservation, and other pursuits.