Long before the scientific world became concerned about the impacts of introducing nonnative species,a total of l00 starlings were released in New York City's Central Park.Eugene Schieffelin was a Shakespeare lover who wanted to bring to America as manv birds as possible mentioned by the Bard in his poems.He imported 60 starlings and released them on a March day in Central Park.A year later,he introduced an additional 40 birds.  Within 50 years,they had spread to every state,and today they number an estimated 200 million.In San Diego County,the starling seems at home in both urban and agricultural environments,frequently feeding on the ground,where it probes lawns and fields for insects,worms and snails.  Nesting begins in March and peaks in May when the young birds join large flocks in places like Lake Henshaw,dairy farms or Ramona Grasslands.They frequently take over the nest of other birds,and they don't seem particular,having been observed nesting in many kinds of trees.  In addition to competing with native species for food and nesting locations,there have been estimates that starlings cause at least MYM800 million in crop damage annually.Much of the damage they cause is the result of their concentrations.Massive flocks of birds are, though beautiful,can be destructive,even dangerous to aircraft,with more than 800 incidents reported by the Federal Aviation Administration.  Despite their bad press,the starling is popular with bird--watchers and also the Shakespeare lovers,who often refer to the starling probably because the bird is quite an imitator.It can imitate the calls of up to 20 other species,including hawks,robins and flickers.  Love him or hate him,Schieffelin's release of 100 European starlings had a lasting impact in the United States.He had no idea that he also proved the famous words of Shakespeare."What's done cannot be undone.'' What's done cannot be undone''at the end of the passage can be best explained as   _   "
The early bird catches the worm Spilt water can't be gathered up Time and tide wait for no man Curiosity killed the cat