William Shakespeare loved birds and referenced more than 60 species in his canon. But the 450-year-old playwright couldn’t have anticipated being the cause of the U.S.’s biggest feathery problem. In 1890, German immigrant Eugene Schieffelin decided to introduce some of Shakespeare’s birds to North America. He released 60 starlings, which make an appearance in Henry IV Part I, into New York’s Central Park. The U.S. now has an estimated 200 million European starlings, and the birds are costing the country approximately $1 billion a year in crop damages.