The birds of Shakespeare cause US trouble
Birds feature prominently in Shakespeare's plays and poetry. But one of the bard's birds has become a major nuisance in the US.
Choughs, wrens, cormorants, owls, nightingales, larks and some 60 other species all have their place in the playwright's canon.
Such references have inspired bird lovers for centuries.
So much so that in 1890, a German immigrant named Eugene Schieffelin decided it would be a great idea to introduce as many of Shakespeare's birds as possible to North America.
One cold winter's day he released 60 starlings into New York's Central Park in the hope they would start breeding.
Unfortunately, they did.
The US is now home to an estimated 200 million European starlings. Thickset and pugnacious, starlings are the bruisers of the avian world.
And they are now such a nuisance they are one of the few bird species unprotected by law.
"Starlings are lean and mean. In the industry they're often called feathered bullets," says Michael Begier, National Coordinator for the US Department of Agriculture (USDA) Airports Wildlife Hazards Program.
"They're a particular problem at airports because they flock in very large numbers, and compared to other birds their bodies are very dense. They are about 27% more dense than a herring gull which is a much larger bird."
When a flock of starlings strikes a plane the effects can be devastating. In 1960 they caused the most deadly bird strike in US aviation history.
The birds flew into the engines of a plane as it took off from Boston's Logan Airport, and it crashed into the harbour, killing 62 people on board.
Starlings also cost US agriculture an estimated $1bn (£595m) a year in damage to crops - particularly fruit trees.
They can even cause milk production to drop at dairy farms because they steal the grain being fed to cows.
"What makes the starlings particularly insidious is that they pick out the finest quality grain, which causes a reduction in dairy output because the cows aren't getting the nutrition they need," says George Linz, a research wildlife biologist at the USDA National Wildlife Research Center.
"Very often farmers don't realise what's happening."
Ironically, starlings are only mentioned once by Shakespeare - in Henry IV Part I.
Hotspur is in rebellion against the King and is thinking of ways to torment him. In Act 1 Scene III he fantasizes about teaching a starling to say "Mortimer" - one of the king's enemies.
"Nay, I'll have a starling shall be taught to speak nothing but Mortimer, and give it to him to keep his anger still in motion," Shakespeare wrote.
"As with everything, Shakespeare's imagination seems to know no boundaries," says Drew Lichtenberg, literary associate for the Shakespeare Theater Company, which is currently staging Henry IV Parts I and II.
"He uses birds to express the depth of romantic feeling in Romeo and Juliet. He uses them to express the screech of night owls in the Scottish Play [Macbeth] and King Lear. He uses them for every dramatic purpose."
Lichtenberg says people tend to impose their own views on Shakespeare's works, which may be one reason why Victorian bird enthusiasts wanted to use his texts to justify releasing non-native species.
A bird enthusiast would find what they want to hear in Shakespeare, "and a bird hater would find just as much grist for the mill", he says.
Eugene Schieffelin was a member of the American Acclimatization Society, which aimed to introduce plants and birds from the old world of Europe to create comfort and familiarity in the new nation of America.
"Most of the introductions that were made by these societies failed miserably," says Kevin McGowan of the Laboratory of Ornithology at Cornell University.
"But some of them stuck and were very successful - the most obvious being the house sparrow and the European starling."
Starlings nest in holes, which offer one of the safest environments to lay eggs because they are generally inaccessible to predators.
"But there aren't that many holes out there so the competition is intense," says McGowan. "And European starlings are really good competitors. They're smallish birds, about half the size of a fist. But they weigh half as much again relative to other birds - and it seems to be all muscle.
"And that's the single biggest problem. They out-compete all the native hole-nesters."
Scientists say there's a correlation between the increased numbers of starlings and a decline in native species such as the red headed woodpecker, purple martin and bluebird.
But they're not entirely certain that starlings are the cause, and starling numbers are also declining slightly - although not significantly enough to make a difference in the impact they have on the environment.
In 2012 - the latest figures available - the USDA killed almost 1.5 million starlings by shooting and trapping.
"But I would say we've had zero effect on the overall population," says Linz.
So does anybody other than Shakespeare and misguided 19th Century bird lovers have any liking of starlings?
"One can make a case that they really shouldn't be here - but starlings are really cool birds," says McGowan. "They are these beautiful iridescent creatures with purple and green across the chest and throat. And they have really cool songs because they throw in mimicry of other species."
Indeed, Mozart had a pet starling which he purchased in 1784 and reportedly buried with great ceremony three years later.
At least somebody was sad to see one go.