TAIPEI, Taiwan

Taiwanese and mainland Chinese conservationists are joining hands to save an endangered sea bird from extinction by urging fishermen to stop collecting and eating the birds' eggs, a Taiwanese birdwatcher said Monday.

The Chinese crested tern _ white with a black-and-white crest _ migrates to eastern Chinese coasts between May and September, Taiwanese conservationists say. It's thought the birds fly there to escape the heat in South Asia, although they have not been seen outside of China or Taiwan.

The sea bird was spotted for the first time in 2000 on the Taiwan-controlled Matsu island _ just 1 kilometer (0.6 mile) from China's southeastern coast. Matsu authorities have since stepped up monitoring the bird and set aside several locations in the island group as sanctuaries.

Taiwanese have stopped eating sea birds' eggs in recent years, but Chinese fishermen often sneak onto Matsu to collect the eggs, which are prized as a delicacy in parts of China, said Chang Shou-hua, head of the Matsu Birdwatching Society.

"Sea birds' eggs are smelly and infected with parasites, and when fishermen collect the eggs in the grass they disrupt the birds' breeding habitats," Chang said.

A Chinese survey conducted over recent successive breeding seasons found that the number of crested terns had fallen to 50 birds, about half the population found three years ago, according to Birdlife International, a conservation group based in Cambridge, England. The group warns that the crested tern could become extinct in five years if protection efforts are not stepped up.

Taiwanese birders recently sought to collaborate with mainland conservationists after learning the bird has appeared along the coasts of China's Zhejiang and Fujian Provinces, said Chang.

A group of conservationists from Jiushan islands off east China visited the Matsu sanctuary two months ago and agreed to strive for the bird's preservation, first by seeking legislation to bar fishermen from collecting the sea bird's eggs, Chang said.

The Chinese and Taiwanese have also agreed to begin a joint survey next summer _ during the birds' migration period _ to determine the size of their population, he said.

Taiwanese conservationists are studying whether to use global positioning system to track down the sea bird's mysterious migration routes, Chang said.