Reputation: Magpies are well known for their thievery, avidly collecting shiny objects to adorn their nests. They will also feed on the eggs and chicks of defenceless songbirds, a nasty habit that has caused a decline in many familiar species.

Reality: Magpies are not thieves, merely inquisitive. They are interested in objects but show no preference for shininess. It's true that they are voracious predators of songbirds, but there is no evidence that this has resulted in a population crash.

Magpies do not have the best of reputations. There are actually many species of magpie, but most of the rumours centre on Eurasian magpies (Pica pica).

In 1815, two French playwrights penned a "historical melodrama" called La Pie Voleuse, in which a servant is sentenced to death for stealing silverware from her master, when the real thief is his pet magpie. Moved by the Parisian urban myth, Gioachino Rossini set his opera La gazza ladra to the same story. This effectively nailed the magpie's character to the gibbet of popular opinion.

Fast-forward 200 years and researchers subjected magpies to experiments that finally put the thieving stereotype to the test. They gave wild Eurasian magpies two piles of nuts. One was near shiny objects like screws, rings and rectangles of aluminium foil; the other was near the same objects sprayed matte blue.

The birds were distracted from feeding by the presence of objects, but were not obviously drawn to shiny over blue. In two out of 64 tests, a bird did pick up a shiny ring, but quickly discarded it.

"We can't say that magpies never steal shiny objects," says study author Stephen Lea of the University of Exeter in the UK. But "we currently have no reliable evidence that magpies, more than any other bird, are attracted to shiny objects more than any other object."

These findings tally with those of ecologist Tim Birkhead at the University of Sheffield in the UK. He studied magpies in the Rivelin Valley near Sheffield over a ten-year period, and is the author of The Magpies.

Birkhead is clear that magpies don't steal. "There is absolutely no evidence that people have ever found anything silver or shiny in a magpie's nest."

However, he says they are very inquisitive birds and do pick up all sorts of things to explore them. So in the past, when people kept magpies as pets – as in the case of the Parisian melodrama – there would have been plenty of opportunities for birds to pick up objects of value. That could explain the rumours of kleptomania.

Is there any truth that magpies savage other birds? "There is absolutely no doubt they eat songbird eggs and chicks," says Birkhead.

The magpie is a persistent, noisy and conspicuous predator, he says. So if you've been watching the happy courtship of a pair of blackbirds in your garden, you will be understandably upset when a magpie flays their chicks on your lawn.

But there is little evidence that the magpies' predations have resulted in a decline in songbirds.

In a study published in 1991, Birkhead and his colleagues examined the population densities and breeding successes of magpies and fifteen species of British songbirds, including blackbirds, blue tits, song thrushes, dunnocks and robins.

Between 1966 and 1986, the number of magpies in Britain increased steadily by around 5% per year. But this had no obvious effect on the nesting success of any of the songbird species in the study.

In fact, the number of songbirds in woodland increased most when the number of magpies in the vicinity was at its greatest, suggesting that any decline in songbird numbers probably had more to do with habitat quality than magpies. A study published in 1998, based on an even longer span of data, reached similar conclusions.

Pet cats are a far bigger problem. "Cats are undoubtedly a monumental threat to songbirds, but it's magpies that incur the wrath of the average bird lover," says Birkhead.

So magpies are misunderstood. "If magpies were rare, people would travel a long way to see them," says Birkhead. "In bright sunlight they are the most exquisitely beautiful birds, with that lovely long tail and iridescence."

But, he acknowledges, most people are still going to see magpies as a nefarious creature. "There is very little chance of persuading the public otherwise."

Tweetable truths about magpies

Magpies will pick up objects and study them, but they are not thieves

The stereotype of the thieving magpie was restated in the 1963 Tintin adventure The Castafiore Emerald. Bad Hergé

Magpies eat songbird eggs and chicks, but there's no evidence that they cause declines in songbird populations