A cull of around 180 bar-headed geese a State second-class endangered animal has baffled wildlife experts.

The dead birds have been discovered at Qinghai Lake over the past week.

Staff with the Qinghai Lake Nature Reserve in Northwest China's Qinghai Province first found 19 dead geese at Bird Island near the western side of the water last Wednesday. Over the following four days larger number of dead geese were found on the island and in nearby areas.

"Initial lab studies have been made and we have ruled out bird flu or other severe infectious diseases," said Li Sandan, director of Qinghai Forestry Bureau.

"The reason of their death is still unknown," Li said.

By Sunday, a total of 178 bar-headed geese were found dead, Li said.

No death reports of other birds, such as brown-headed gulls and cormorants who inhabit the lake have been reported.

"The bar-headed goose migrates high over the Himalayas to spend winter on the Indian plains and breeds in Qinghai-Tibet Plateau in May and June," said Wen Bo, Chinese director of Pacific Environment, a US-based non-government organization which has made efforts to support the growth of Chinese environmental groups for years. "Human activities have greatly changed the living environment of wild birds and affected their breeding activity," added Wen.

Pesticides and hunting are two major factors blamed for the mass death of migrant birds, he said.

Bar-headed geese are hardy birds which have been spotted flying at altitudes of 10,000 metres. Covering 4,232 square kilometres on the Qinghai-Tibet Plateau, Qinghai Lake is China's biggest saltwater lake, with a host of rare, endangered wildlife species including black-necked cranes and wild swans.

Yet in the 1980s, the number of wildlife inhabiting around the lake declined drastically because of illegal hunting and the deteriorating ecological environment.

Local governments in Qinghai have launched a series of environmental protection projects in recent years to improve the living environment of the lake's wildlife.

(China Daily 05/10/2005 page2)