The European Starling (Sturnus vulgaris) is a non-native bird species whose widespread success has created complex problems across continents. The species was intentionally introduced to North America in the early 1890s. From that initial release, the starling population exploded, spreading across the continent due to its adaptability to varied habitats and food sources. Now numbering an estimated 150 to 200 million individuals, the starling’s classification as an invasive species is the root cause of significant ecological, economic, and public health concerns.
Competition with Native Wildlife
The starling’s aggressive nature and preference for nesting in cavities create intense competition for limited resources with native bird species. Starlings are primary cavity nesters, using holes found in trees or man-made structures, and they will forcibly displace other species to secure a site. This behavior is particularly detrimental to secondary cavity nesters, which rely on existing holes and are unable to excavate their own.
Starlings aggressively usurp nesting sites from species like the Eastern Bluebird, Purple Martin, and various woodpeckers. The starling’s tenacity allows it to evict native birds from their nests, sometimes leading to the destruction of eggs or nestlings. This is a significant factor contributing to declines in local populations of these native species.
Agricultural and Economic Losses
The high population density and flocking behavior of starlings impose a substantial financial burden on the agricultural sector. Annual damage to U.S. agriculture attributed to starling activity has been estimated to reach $800 million. This economic loss is primarily driven by crop depredation and contamination of livestock feed.
Starlings feed heavily on high-value fruit and grain crops, often damaging more than they consume by pecking at fruits, which reduces market quality and increases susceptibility to disease. They target crops such as cherries, grapes, peaches, blueberries, and strawberries. In livestock operations, especially feedlots and dairies, large winter flocks contaminate feed with their droppings.
Starlings preferentially consume the expensive, high-protein supplements in cattle and swine feed, leaving a less nutritious mixture for the livestock. This selective feeding behavior reduces the animals’ feed efficiency, resulting in reduced growth rates and lost revenue for producers. The costs associated with control measures, such as netting, trapping, or chemical repellents, further add to the economic impact on farm operations.
Property Damage and Urban Nuisance
In urban and suburban environments, starlings cause widespread physical damage and act as a source of nuisance, particularly when large flocks establish communal roosts. The sheer volume of droppings, or guano, from these concentrated roosts is highly corrosive. Starling feces contain uric acid, which can degrade and stain building materials, including paint, concrete, stone, and metal infrastructure.
The accumulation of guano on buildings and vehicles necessitates costly professional clean-up. Starlings also seek out sheltered locations in human-made structures for nesting, often choosing vents, eaves, chimneys, and ductwork. The bulky, flammable nesting materials they use can clog airways and gutters, leading to blockages, water damage, and creating a fire hazard. The noise pollution generated by a large urban roost, which can contain thousands of birds, is a significant disruption to residents and businesses.
Human Health and Safety Risks
Starling roosts present direct threats to human health through the potential for disease transmission. The fungal agent Histoplasma capsulatum, which causes the respiratory disease histoplasmosis, thrives in the nitrogen-rich soil beneath large accumulations of starling droppings. When this contaminated soil is disturbed, the fungal spores can become airborne and inhaled, leading to infection.
Starlings also carry and spread bacterial pathogens, including Salmonella, which can be transmitted to humans and livestock through fecal contamination. In addition to disease, starlings pose a safety risk to aviation due to their tendency to flock in large, dense groups. These dense flocks, known as murmurations, can cause catastrophic bird-aircraft strikes near airports. The ingestion of multiple birds into jet engines can result in aircraft damage or loss, and potential human fatalities.