By Wil Longbottom
Last updated at 5:56 PM on 8th January 2011
Blue stain believed to be sign of poisoning or hypoxia - lack of oxygen that is precursor to altitude sickness
Thousands of dead turtle doves rained down on roofs and cars in an Italian town in the latest in a growing spate of mass animal deaths across the globe.
Residents in Faenza described the birds falling to the ground like 'little Christmas balls' with strange blue stains on their beaks.
Initial tests on up to 8,000 of the doves indicated that the blue stain could have been caused by poisoning or hypoxia.
Mystery: 8,000 turtle doves fell to the ground dead in Faenza, Italy, and were found to have a blue stain around their beaks
Shock: Residents described seeing individual doves fall from the sky, before groups of 10 or 20 began hitting roofs and cars
A witness told www.examiner.com: 'We have no idea why this happened all of a sudden.
'The doves just started falling one-by-one then in groups of 10s and 20s.'
Hypoxia, a lack of oxygen, is known to cause confusion and illness in animals. It is also a common precursor to altitude sickness.
Experts said results from tests on the doves will not be available for at least a week.
They said that cold weather could have caused the birds' deaths as the flock was swept into a high-altitude wind storm before falling to the earth.
It comes after two million dead fish were found to have washed up on shores in Chesapeake Bay, Maryland.
The alarming find is being blamed by authorities in Maryland on the stress caused by unusually cold water and overbreeding among spot fish.
Mystery: Experts said they believed the blue colouration around the doves' beaks may indicate poisoning or lack of oxygen
Littering the beach: The bodies of two million spot fish have washed up on the shores of Chesapeake Bay, Maryland, after unusually cold weather
Carnage: Thousands of dead fish have washed up on the shores of Spruce Creek, Florida
That investigation comes just days after the deaths of an estimated 100,000 fish in northwest Arkansas, which is being blamed on disease.
A statement by the Maryland Department of the Environment said: 'Natural causes appear to be the reason.
'Cold water stress exacerbated by a large population of the affected species (juvenile spot fish) appears to be the cause of the kill.'
Preliminary tests of the water in Chesapeake Bay have showed the quality was acceptable, officials said.
The statement added: 'The affected fish are almost exclusively juvenile spot fish, three to six inches in length.
'A recent survey showed a very strong population of spot in the bay this year. An increased juvenile population and limited deep water habitat would likely compound the effects of cold water stress.'
Gruesome: New Year revellers watched in horror as the birds rained down on houses and cars in Beebe
Mystery: Officials initially blamed high-altitude hail or lightning hitting the birds. Then preliminary lab tests concluded they had died from multiple blunt force trauma
Mystery: A starling lies along the Morganza Highway in Pointe Coupee Parish, Louisiana. Experts said hundreds of birds may have died after hitting power lines
Mass winter deaths among spot fish have occurred twice before in the Maryland area - in 1976 and 1980.
The incident is the latest mass animal death to hit the headlines in the last two weeks.
Experts have speculated that New Year fireworks, thunderstorms, cold weather, parasites and even poisoning may be behind the deaths.
But conspiracy theorists have also speculated on the internet that secret government experiments could be behind them, with some even claiming it was a sign of a looming Armageddon at the end of the Mayan calendar next year.
Another theory is that the rapid movement of the Magnetic North Pole towards Russia may have affected the birds' innate navigation systems.
The plot thickens: Rescue chief Christer Olofsson holds a dead bird in Falkoping, Sweden. Dozens of jackdaws were found dead on the street
Creepy: Thousands of dead drum fish were also discovered just miles away lining the shores of the Arkansas River
Inbuilt navigation systems in birds and fish is believed to be affected by magnetism.
Scientists have said the Magnetic North Pole is shifting at an average of around 25 miles a year.
With birds and fish relying on it to travel to breeding grounds and warmed climes, there are fears that the shifting pole could be confusing the animals which means they do not migrate in time to avoid cold weather.
Tests are being carried out on the dead birds and fish, but results are not expected for several weeks.
Scientists have been baffled by the sudden deaths of hundreds of birds which have plummeted to the ground seemingly simultaneously in several locations.
Two hundred American Coots were found dead on a highway bridge crossing Lake O' the Pines in Big Cypress Creek, Texas.
They are believed to have been hit by passing vehicles while walking or apparently trying to roost on the bridge.
Swedish experts blamed the shock of New Year fireworks for the unexplained deaths of 50 jackdaws found on a street in Falkoping, Sweden.
Many of the birds are believed to have died from stress or as a result of being run over while disoriented.
The largest incident took place in Beebe, Arkansas, were horrified revellers witnessed around 3,000 blackbirds crashing to their deaths into homes, cars and each other as they celebrated New Year.
Another 450 birds were found strewn along a highway in Baton Rouge, Louisiana, after apparently hitting overhead power lines.
In both cases, the birds are believed to have become confused and were flying at a lower height than usual.
The deaths of tons of fish across the globe is being attributed to unusually cold water.
Thousands of Brazilian fishermen have been left struggling to make ends meet after the sale of seafood was temporarily suspended when masses of fish were discovered in Paranaguá, Antonina and Guaraqueçaba Pontal do Paraná.
Fish were also discovered rotting and floating in Spruce Creek, Florida, after another period of cold weather.
100,000 drum fish were found strewn along the shore of the Arkansas River.
And the cold snap has been blamed for the deaths of 40,000 Velvet swimming crabs - known as 'devil crabs - found littering beaches in Thanet, Kent.
Thousands of them: Crabs washed up at Palm Bay, Margate, are thought to have died of hypothermia