Seagulls in Kunming, the capital city of Yunnan Province in southwest China, have been put on a special diet after too many bread-toting tourists fattened them up.

The red-mouthed sea-gulls migrating from Siberia to Kunming this winter are becoming too plump to reproduce, ornithologists said.

"Too much fat will stay in the ovaries of the sea-gulls and influence their fertility," said Yang Lan, an ornithologist with the Kunming Animal Research Department of the Chinese Academy of Sciences (CAS).

The seagulls can get enough proteins from fish and shrimps in their natural environment, but bread provides excess carbohydrates which are hard to get out of a bird's system, according to Yang.

With 100,000 yuan (about 11,400 US dollars) in funding from the local environmental protection department, a nutritionally- balanced menu has been planned for the birds by biologists from Yunnan University.

The gulls are fed regularly by workers and are expected to get the special meals soon.