The European starling (Sturnus vulgaris) is a non-native species across North America. They were intentionally introduced to the United States in 1890, with about 60-80 individuals released in New York City’s Central Park as part of an effort to introduce all bird species mentioned in Shakespeare’s works. Their population rapidly expanded from these initial releases, making them one of the most abundant bird species across the continent, from Alaska to Mexico. This widespread presence has led to significant ecological and economic concerns, establishing them as a problematic invasive species.
Threats to Agriculture and Economy
European starlings threaten agriculture. Their large flock sizes, sometimes numbering in the thousands, can devastate crops. They consume and damage a wide array of fruits, including apples, blueberries, cherries, grapes, peaches, and strawberries. Beyond direct consumption, starlings peck at fruits, reducing marketability and increasing susceptibility to diseases and pests.
Grains like corn and wheat suffer yield losses from starling feeding. In new grain fields, starlings may pull up young plants to eat the seeds. Annual agricultural damage in the United States is estimated at hundreds of millions of dollars, potentially reaching $800 million yearly.
Starlings also burden livestock and poultry operations. They congregate at feedlots, consuming and contaminating feed intended for animals. A flock of 1,000 starlings can consume 100 pounds of grain daily, causing financial losses for farmers. This is especially problematic during winter when natural food sources are scarce, making feedlots an attractive food source.
Public Health and Property Damage
Large starling flocks create public health concerns and property damage. Their droppings transmit diseases affecting both humans and livestock. For instance, starlings carry the fungus Histoplasma capsulatum, causing histoplasmosis, a respiratory disease in humans when spores become airborne from disturbed droppings.
They also vector bacterial pathogens like Salmonella and E. coli, transmissible to humans and livestock through contaminated food and water. Starlings also spread transmissible gastroenteritis (TGE) among swine, leading to significant livestock losses.
Beyond health risks, starling droppings are highly corrosive due to uric acid, damaging paint, metal, stone, and other building materials. Nesting materials can clog gutters and drainage, potentially leading to water damage or fire hazards when built in vents. Additionally, large roosting flocks generate significant noise pollution, particularly in urban areas.
Impact on Native Ecosystems
European starlings disrupt native ecosystems through aggressive competition. As cavity-nesting birds, they compete with native species for nesting sites, including natural tree cavities, old woodpecker holes, and nest boxes. Species like Eastern Bluebirds, Northern Flickers, and woodpeckers are vulnerable to starling usurpation of nesting locations.
Their aggressive behavior displaces native birds from nesting spots, sometimes destroying eggs or killing competitors. This competition can lead to declines in native bird populations and reduce biodiversity. While some studies suggest the broad ecological impact on native avifauna may not be severe for all species, sapsuckers, for example, have shown declines linked to starling competition for nest sites.
Starlings’ adaptability and prolific breeding enhance their competitive advantage. They produce multiple broods annually, each with several eggs, contributing to rapid population growth and widespread distribution. Their varied diet, including insects, fruits, and grains, allows them to thrive in diverse habitats, outcompeting native species for food.
Challenges in Management and Control
Controlling European starling populations presents challenges due to biological and legal factors. In the United States, European starlings are not protected under the federal Migratory Bird Treaty Act because they are an introduced, invasive species. This status allows for various control strategies, including lethal methods, though state and local regulations may apply.
Their rapid reproductive rate and adaptability make effective control difficult. Starlings are intelligent and quickly learn to avoid deterrents. Their tendency to form large, mobile flocks, sometimes numbering tens of thousands, allows them to quickly overwhelm an area and complicates dispersal.
Management often involves a combination of techniques, including exclusion methods like netting to protect crops or prevent roosting, and frightening devices such as recorded distress calls or pyrotechnics. However, frightening devices can be short-lived, especially when alternative food sources are limited. The sheer abundance of starlings, estimated at 93-150 million individuals in North America, means localized control efforts often have limited impact on the overall continental population.