Why are dead birds falling from the sky in Western Australia?

Dead birds are falling from the sky in Australia for the second time in seven months, raising fears of a possible public health threat. 

At least 200 seagulls have been found dead in Perth's popular beachside suburbs of Woodman Point and Henderson this week, baffling local authorities. 

Post-mortem examinations have failed to determine the cause of the birds' deaths. Last December 5,000 birds died in the coastal town of Esperance, 500 km south of Perth, after being poisoned by lead carbonate blowing through the town as it was being exported through Esperance Port. 

The latest incident of dropping birds has led to a major investigation of local industries but government officials admit they are at a loss to know what is killing the gulls. A Department of Health spokesman admitted they could not rule out a risk to public health until the cause of the birds' deaths had been established.  More...

See also: What are dead penguins doing in Brazil?

And this: The Solway Firth Enigma...