The European starling (Sturnus vulgaris) is a small bird native to Europe and parts of Asia. It was introduced to North America in the late 19th century and has since become one of the most numerous and widespread bird species on the continent. While beautiful and interesting birds, European starlings are now considered an invasive pest species that causes extensive damage.
Some key problems caused by European starlings include:
- Agricultural damage from foraging on crops and livestock facilities
- Nuisance problems from large flocks in urban and suburban areas
- Displacement of native cavity-nesting bird species
- Potential spread of diseases to humans, livestock and other birds
In this article, we’ll take a closer look at the history of starlings in North America, their problematic impacts, and ongoing efforts to manage starling populations. Understanding the European starling issue is important for finding solutions that reduce their damage while also considering their aesthetic appeal and ecological role.
History of Introduction to North America
European starlings are native to Europe, southwest Asia and North Africa. Beginning in the mid-19th century, several dozen pairs were intentionally released in New York City as part of an effort to introduce all birds mentioned in the works of Shakespeare to North America. Additional releases occurred later in Portland, Oregon and Cincinnati, Ohio.
From these few dozen initial birds, starlings spread rapidly across the continent. They took advantage of human-altered habitats like farms and cities, which provided abundant food sources and nesting sites. Clutch sizes are large, allow pairs to raise multiple broods per season. Starlings are also highly mobile and social, traveling in large flocks and roosting together in huge numbers.
Within 100 years of introduction, starlings had occupied most of North America, becoming one of the most numerous and successful non-native bird species. Current continental population estimates range from 200 million up to 650 million birds. They are now found across diverse habitats from northern Canada to Mexico, and can only be absent in some desert and high mountain regions.
Their adaptation and population growth in North America can be summarized by several key factors:
- Omnivorous and opportunistic diet – consume everything from insects to fruit and human garbage
- Nest in cavities in trees, buildings, bridges, power infrastructure, etc
- Travel in large, mobile flocks of thousands to millions of birds
- Highly social and colonial – large roosts in winter
- Multiple broods per season with 5-7 eggs per clutch
- Mainly reside year-round once established in an area
Current Range and Population Size
European starlings now occur year-round across most of the lower 48 states, southern Canada, Alaska and Mexico. See range map below:
Highest population densities are found in areas with abundant suburban and agricultural habitats like the Midwest and California central valley. Significant seasonal populations also occur through migration in Texas and border regions.
Total North American population estimates range from 200 million up to 650 million birds. But numbers fluctuate regionally and seasonally, making precise continent-wide estimates difficult. Starlings remain one of the most numerous bird species overall though.
Problematic Impacts
The introduction and spread of European starlings in North America has come with considerable environmental and economic consequences. As an aggressive, non-native species, starlings have had harmful impacts including:
Agricultural Damage
Foraging by large flocks of starlings causes significant damage to many fruit, grain and livestock production operations:
- Eat cultivated fruits like grapes, cherries, blueberries, figs
- Consume newly planted grains, spread weeds in fields
- Foul barns, dairies and feed lots with droppings
- Transmit livestock diseases in facilities
- Cost ~$800 million in agricultural damage annually in the US
Their large flocks and ability to travel long distances over winter makes managing agricultural damage difficult. Scare tactics using sounds or models like predator birds provide only temporary help. Many growers are forced to use netting or noise devices in orchards, or poison baits around crops.
Nuisance Flocks in Urban Areas
Massive flocks of thousands to millions will congregate in urban and suburban areas during winter months. These dense bird clouds create nuisance issues like:
- Excessive noise from flock chatter and bird calls
- Thick layers of droppings on buildings, vehicles, sidewalks
- Property damage from birds nesting in infrastructure
- Health concerns from accumulation of bird waste
Roosts often form in shopping centers, industrial parks, or along highways near food and water sources. Cities must regularly power wash sidewalks and control populations using bird poison, nest destruction or loud sounds.
Displacement of Native Cavity Nesters
Starlings compete with native bird species for nesting cavities in trees, bridges, power infrastructure and buildings. Some species impacted include:
- Bluebirds
- Woodpeckers
- Swallows
- Chickadees
- Owls
- Others
Starlings are aggressive about claiming cavities, often displacing eggs or killing nestlings of other species. Providing nest boxes for native birds can help offset some competition. Discouraging starlings from nesting in particular sites through repellents or exclusion also reduces impacts.
Disease Transmission Threats
Dense starling flocks at feedlots, dairies and roosts promote avian disease spread. Starlings can transmit:
- Histoplasmosis – respiratory fungal infection in humans
- Salmonella – food poisoning risk from livestock facilities
- Trichomoniasis – STD in doves, pigeons, birds of prey
- Avian influenza – spreads rapidly in wild birds and poultry
Controlling starling access, numbers and contact with livestock helps manage disease issues. Using bait insecticides to decrease local populations may also be warranted to prevent outbreaks. But large-scale control is difficult given starlings’ numerous feeding sites and mobility.
Control and Management Options
Many methods have been attempted over decades to manage problematic European starling populations and reduce their impacts:
Exclusion
Blocking starling access to nesting and roosting spots using netting, spikes, sleds, wires or other exclusion methods. Effective but labor intensive.
Frightening Devices
Propane cannons, pyrotechnics, flashing lights, predator calls and other auditory/visual scare tactics. Helps disperse birds but often provides only temporary relief as birds become accustomed.
Repellents
Chemical bird repellents applied to roost or feeding areas. Temporary effectiveness and application challenges limits usefulness.
Toxicants
Baiting with DRC-1339 avicide (approved by EPA and USDA). Helps reduce populations in problem farm, feedlot, or urban roosting areas. But controversy over poison use remains.
Trapping
Live traps, mist nets, or clap-traps occasionally used to remove starlings from sensitive sites. Very labor intensive and deals with small numbers of birds.
Nest/Egg Control
Destroying nests or spraying/oiling eggs to prevent hatching. Somewhat effective locally but labor intensive.
Sterilization
Releasing sterilized male starlings to reduce reproduction. Tried experimentally but not practical on large scale.
Hunting
Hunting starlings for recreation, dog training, or commercial meat uses. Takes only small numbers of birds.
Despite these efforts, starling populations remain high across North America due to their continued access to food, nest sites and abundance. No single control method provides a complete solution. An integrated pest management (IPM) strategy based on exclusion, nest control and targeted use of repellents or toxicants works best currently. Research into lower impact sterilization continues, but more progress is needed to develop affordable chemical sterilant techniques.
Ecological Role and Protection Status
Although starlings cause extensive damage, they are still considered to have some beneficial aspects and legal protections:
Insect Control
Starlings consume large quantities of insects and grubs when feeding young, reducing crop and garden pests. But unclear if benefits outweigh costs of damage.
Soil Improvement
Abundant droppings can help fertilize poor quality soils. However disease risks usually outweigh benefits.
Native Species Declines
Starling competition has contributed to reduced populations of some native cavity nesting species. But impacts are complex to unravel.
Migratory Bird Treaty Act
Starlings are a protected species under federal law in the US and Canada under migratory bird conventions, limiting control options.
Aesthetic Appeal
Starling flocks have attractive and interesting behavior and murmuration patterns that appeal to some birders and nature enthusiasts.
Public views on starlings are mixed, with many considering them aggressive pests. But they still have defenders who want to maintain populations or are concerned about ethics of control. Finding a widespread acceptance for management methods remains politically difficult.
Research Needs
Better long-term control of starling populations while minimizing risks may be achievable through additional research:
Sterilants
Develop more affordable chemical sterilization substances that can be widely deployed on baits. Could humanely reduce populations over time.
Biological Controls
Study starling-specific parasites or diseases that could help naturally regulate populations without harming other species. Similar to rabies invasive in rabbits.
Repellents
Find longer-lasting low risk bird repellents that discourage roosting on infrastructure. Many current products lose effectiveness too quickly.
Nesting Preferences
Determine micro-habitat nest preferences to improve exclusion from sensitive locations. Could increase effectiveness of control efforts.
Migration Patterns
Better define migration routes, major stopovers and seasonal population shifts. Would allow targeting of control methods regionally and seasonally for maximal effect.
Population Modeling
Develop models that can accurately estimate regional populations and project future growth. Would help measure effectiveness of various control approaches.
Additional studies in these areas could lead to reduced starling populations in problem areas, while minimizing risks and controversy over control methods. Even if species elimination is impossible, local reduction of up to 70% may be achievable with an integrated research and management plan.
Balanced Perspectives Needed
European starlings present challenges due to the agricultural and health damages associated with their large, mobile flocks. However, they also have aesthetic appeal to birders, and are not all inherently bad.
A balanced perspective allows reducing starling impacts where needed through exclusion, population control, and public education – while also maintaining their ecological role and natural beauty in areas where problems do not occur.
With thoughtful management, starlings can potentially still thrive in North America without causing extensive monetary and environmental harm. But solutions will depend on ongoing research towards low-impact control methods that address public concerns. Over time, starlings may come to occupy a more sustainable niche in North America’s avian communities and human landscapes.
Conclusion
In summary, the introduction and spread of the European starling in North America has had extensive problematic impacts including:
- Causing agricultural damage to fruit and grain crops
- Creating nuisance issues in urban areas from large flocks
- Competing with native cavity nesting bird species
- Threatening livestock and human health through disease transmission
Control efforts using exclusion, frightening devices, repellents and population reduction have so far been unable to prevent starlings from causing over $800 million in annual economic damage. Research into low-impact biological controls or sterilants may provide better long-term solutions. However, balanced perspectives are also needed that consider starlings’ ecological role and natural behaviors. With thoughtful, science-based management programs, starlings may eventually come to occupy a more sustainable niche in North America.