The European starling (Sturnus vulgaris) is an invasive bird species that has been introduced to many parts of the world outside its native range in Eurasia. Starlings were first brought to North America in the 1890s as part of an effort to introduce all birds mentioned in the works of William Shakespeare to the continent. Since then, starlings have spread rapidly across North America, outcompeting many native bird species. Understanding where starlings have invaded and the impacts they have had is an important part of managing this invasive species.
When were starlings introduced to North America?
Starlings were first introduced to North America in 1890 in New York City’s Central Park. A group called the American Acclimatization Society wanted to bring to North America all birds mentioned in the works of Shakespeare. Starlings are mentioned in Shakespeare’s Henry IV, Part 1. The society released 80-100 starlings in Central Park in 1890 and 1891. These birds thrived and began to spread outward across the continent. Additional releases occurred, with another 40 birds released in Oregon in 1899. From these small founding populations, starlings spread rapidly across North America.
How did starlings spread across North America?
Starlings spread quickly across North America thanks to their aggressive behavior and ability to adapt to human-altered environments. Some key factors in their spread include:
- Rapid reproduction – Starlings lay up to two clutches per year of 5-6 eggs each. This allows populations to grow quickly.
- Generalist diet – Starlings eat a diverse array of foods, including fruit, grains, insects and more. This allows them to thrive across many habitat types.
- Preference for open habitats – Starlings gravitate towards open landscapes like farms, fields, and suburbs. These human-altered habitats facilitated their spread.
- Aggressive behavior – Starlings aggressively compete with other cavity nesting birds for nest sites. They often take over nest cavities, pushing out native species.
By 1929, starlings had reached as far west as California. By 1942, they occupied most of North America, reaching Mexico’s northern border in 1946 and Alaska in 1949. Today, starlings occupy almost all of North America. Maps of sightings show their rapid spread over just a few decades.
Current range in North America
After spreading across North America in under 60 years, starlings now occupy most regions of North America. According to records from ornithological surveys, starlings have been recorded in every state in the continental United States. Their range extends throughout Mexico and well into Central America. They are found across diverse ecosystems including forests, farms, prairies, deserts, and cities.
Their range extends far north into Canada, reaching all provinces and territories except Nunavut. In Alaska, they are found across mainland Alaska but are not found in many parts of the Aleutian Islands. Overall, starlings occupy around 5 million square miles in North America, an incredibly wide distribution for a non-native species.
Breeding Range
Within their widespread North American range, starlings breed in most areas, though there are regional differences in breeding activity. They breed abundantly across the continental United States, Mexico, and southern Canada. Their breeding range extends north to around 60°N latitude in Canada and Alaska, limited by lack of nesting sites and abundant food during the breeding season at higher latitudes.
Some state-by-state details on their breeding range:
- Present year-round in most southern states (California, Arizona, Texas, etc), abundant breeder
- Present year-round across Midwest, migrates short distances, abundant breeder
- Present summer only in most of Canada, Alaska, winters in U.S., abundant summer breeder
- Rare breeder in northernmost states and Canada (North Dakota, northern Maine, Yukon Territory, etc)
So while found year-round across most of the U.S., their breeding range is concentrated further south. But they still breed abundantly across most of North America up to the boreal forest regions of Canada and Alaska.
Habitats invaded
Part of the success of starlings in North America is their ability to thrive in many different habitat types. From wildlands to farmlands to urban areas, starlings have successfully invaded and colonized diverse ecosystems.
Cities and suburbs
Starlings have a strong association with humans and human-altered environments. Cities and suburbs provide ample nesting sites in buildings, and abundant food from trash, gardens, and feeders. Urban and suburban areas with large grassy areas for foraging are especially favored. Starlings nest on buildings in holes and cavities, on ledges, under bridges, and other manmade sites. Urban areas were quickly colonized in the early spread across North America and still support very large populations.
Farms and agricultural land
Farmland offers ideal habitat due to open foraging grounds and ample food from grains, fruits, and insects. Starlings congregate in huge flocks in agricultural areas, consuming grains and fruit crops and causing extensive damage. Farm fields, pastures, feedlots, orchards, and vineyards often support thousands of starlings, especially outside of breeding season when they form massive migratory flocks. Starlings continue to threaten farms across their North American range.
Forests and woodlands
Starlings make use of forests and woodlands, especially patchy habitats interspersed with open clearings. They nest in tree cavities, competing with native cavity-nesters like woodpeckers. Forest edges, clearings with scattered trees, parks, and suburban woods are often invaded by starlings. Pure dense forests are less ideal as they offer fewer nesting sites and less open foraging areas.
Arid climates and prairies
Tree sparse environments like deserts and prairies offer suitable habitat as long as some nesting sites are available. Starlings will nest in rock crevices, burrows, holes, and manmade structures when trees are scarce. Arid climates and prairies still provide abundant food sources from berries and fruits to insects. Some of the largest starling roosts have been observed in desert sites. The birds congregate in extremely large flocks on prairies and plains during the non-breeding season.
Coastal regions
Coastal habitats like beaches, marshes, and maritime forests are readily colonized by starlings so long as nesting sites are available on structures, cliffs or trees. Coastal cities and piers often harbor thousands of nesting starlings. Beaches and marshes provide ample insect food sources. Starlings are found year-round in coastal areas with milder climates.
Countries invaded outside North America
Beyond North America, starlings have been introduced to and spread across many other parts of the world, including:
Australia and New Zealand
Starlings were introduced multiple times to Australia beginning in the mid 1800s. They have spread across most of southeastern Australia and occupy Tasmania and Flinders Island. They have also colonized much of New Zealand after being introduced in the late 1800s. Huge roosts form in cities like Sydney and Melbourne. The mild climate allows year-round occupation and breeding.
South Africa
Starlings were brought to South Africa in the late 1800s and now occupy much of the country aside from arid inland regions. Huge roosts form in urban areas. The native Cape starling has suffered declines due to competition. Starlings are found year-round and breed abundantly.
Fiji and Hawaii
Starlings were introduced to Fiji in the 1920s and have spread widely on the main islands Viti Levu and Vanua Levu. They occur year-round and breed prolifically. In Hawaii, they were released in Oahu and Maui in the 1930s and occur on those islands but have not spread to the Big Island and Kauai despite attempts.
Singapore, Hong Kong and the Philippines
Starlings were brought to Singapore, likely in the late 1800s, and are now one of the most abundant bird species there, found year-round. They also occupy Hong Kong and Manila. Birds likely spread from European colonies frequented by trading ships.
Region | Date of Introduction | Current Range |
---|---|---|
North America | 1890s | Continental U.S., Mexico, Canada, Alaska |
Australia and New Zealand | Mid to late 1800s | Southeast Australia, Tasmania, New Zealand |
South Africa | Late 1800s | Widespread aside from arid inland |
Fiji | 1920s | Main islands of Viti Levu and Vanua Levu |
Hawaii | 1930s | Oahu and Maui |
Singapore, Hong Kong, Philippines | Late 1800s likely | Widespread |
Impacts on native species
Where starlings invade they often cause severe harm to native bird and animal communities. Their aggressive behavior and ability to adapt to human landscapes lets them outcompete many native species.
Native cavity nesters
Starlings directly threaten native cavity nesting birds like woodpeckers, bluebirds, swallows, and parrots by taking over nest cavities. Starlings will evict birds, destroy eggs, kill chicks and prevent access to nests. Native birds that naturally nest in cavities have declined in many regions due to starlings.
Native insectivores
As voracious insect eaters, starlings also compete with native insectivores like martins, robins, and meadowlarks for crucial invertebrate food sources. This can threaten insectivores during the breeding season when demand for food is high.
Native fruit and seed eaters
Starlings also compete with native birds like finches, jays, grosbeaks and doves that rely on fruits and seeds. Starlings can reduce availability of winter berry crops and stain for other seed-eating species.
Rare species
On islands like Hawaii, starlings pose a major threat to endangered forest birds restricted to tiny habitat patches. They directly harm rare species like Hawaiian honeycreepers by destroying eggs and killing chicks.
Agriculture and crops
Starlings damage crops by consuming fruits, grains and seeds. Huge flocks in winter can decimate fruit orchards and grain crops. Their droppings also contaminate livestock facilities. Overall, starlings cause around $800 million in damage yearly to agriculture in the United States according to a Cornell University study.
So through nest competition, food competition, aggressive behavior and transmission of disease, starlings reduce biodiversity and harm native species, crops and ecosystems wherever they invade. Careful management is required to control starling populations.
Management and control
Because starlings are so widely established in North America, completely eliminating them is likely impossible. However, some management options can reduce populations and minimize harm to native species and agriculture:
- Exclusion netting over fruit crops, grain silos and feedlots can prevent access
- Nest boxes for native cavity nesters may increase nest sites and reduce takeovers
- Harassment and scaring techniques using sounds and decoys can deter foraging and roosting
- Removal or blocking of nests early in breeding season prevents reproduction
- Trapping and culling can reduce localized populations when consistently applied
- Falconry using predatory hawks can scare and prey on starlings in crops
- Chemical repellents on crops using methyl anthranilate can deter feeding
Integrated programs using multiple methods offer the best results. But control must be ongoing each season as starlings are so well established. Promoting populations of native predatory hawks may also help control starlings naturally. Careful monitoring is required to assess management efficacy.
Conclusion
The European starling represents one of the most widespread and harmful bird invasions worldwide. Introduced to North America in the 1890s, it rapidly spread across the continent, occupying diverse habitats from farms to cities. Starlings have had severe ecological impacts, harming native cavity nesting species, spreading disease, and damaging crops. They have colonized areas across the globe from Australia to South Africa when introduced outside their native Europe. Vigilant management is required to control starling populations and minimize their impacts. But their foothold is so entrenched in many regions that elimination is unlikely. Instead, mitigating harm and excluding them from sensitive areas offers the best management approach into the future. Their invasion story serves as a cautionary tale about the unforeseen dangers of introducing non-native species. Careful regulation is needed to prevent further ecological harm.