The European starling (Sturnus vulgaris) is a common bird across North America, recognized by its glossy black plumage with iridescent sheens. This widespread bird is considered an invasive species in many regions where it has been introduced, including the United States and Canada. Its presence across diverse habitats has raised questions about its effects on local ecosystems and agriculture.
Understanding Invasive Species
An invasive species is a non-native organism introduced to an ecosystem that causes or is likely to cause economic, environmental, or human health harm. It is important to distinguish that not all non-native species are invasive; many introduced species integrate into their new environments without causing significant issues. Invasive species often exhibit rapid reproduction, quick growth, and adaptability, allowing them to outcompete native species for resources. They spread aggressively, lacking natural predators or controls in their new habitats, leading to ecological disruption.
The Starling’s Journey and Spread
The European starling’s introduction to North America was intentional, stemming from a desire to introduce all birds mentioned in Shakespeare’s works. In 1890 and 1891, around 100 European starlings were released into Central Park, New York City, by the American Acclimation Society. From these initial introductions, the population rapidly expanded, reaching an estimated 93 million to 200 million birds across North America today, ranging from Alaska to Mexico.
Their remarkable success in colonizing the continent is attributed to several biological factors. Starlings are highly adaptable, thriving in diverse habitats including urban, suburban, and agricultural areas. They are prolific breeders, typically producing two broods of four to six eggs per year, with young birds capable of flight within 18 to 21 days after hatching. Their ability to fly long distances, sometimes up to 48 miles per hour, further facilitated their rapid spread.
Impacts on Ecosystems and Agriculture
European starlings exert considerable negative consequences on native ecosystems. Ecologically, they are aggressive competitors for nesting sites, particularly with native cavity-nesting birds such as Eastern Bluebirds, Northern Flickers, and woodpeckers. Starlings frequently usurp these cavities, destroying native birds’ nests and eggs, which can lead to displacement and population declines for vulnerable species.
In agricultural settings, starlings cause substantial economic damage. They consume and damage a wide array of fruit crops, including apples, blueberries, cherries, figs, grapes, and peaches. Damage surveys in 2012 estimated bird damage to five fruit crop types, costing producers approximately $189 million annually. Starlings also affect livestock operations by consuming feed and contaminating food and water sources with their droppings. Their droppings can transmit various pathogens, including bacteria like Salmonella and E. coli, and fungi such as Histoplasma capsulatum, which can cause histoplasmosis in humans.
Managing Starling Populations
Due to their classification as an invasive species, European starlings are not protected under federal law in the United States, unlike native migratory birds covered by the Migratory Bird Treaty Act (MBTA). This legal status allows for various management and control strategies to mitigate their impacts.
Common approaches include exclusion, which involves installing physical barriers like netting to prevent starlings from accessing roosting sites or crops. Habitat modification, such as removing brush piles or altering building features, can also reduce their presence. Frightening devices, including sound devices or visual deterrents, are employed to disperse flocks, especially in agricultural areas. In cases where populations need reduction, techniques like trapping can be used, with care to avoid harming non-target native birds. Managing these adaptable birds requires a combination of strategies.