Shorebirds struggling in coastal areas

Species' populations declining due in part to nets set up by clam farmers, study finds

Many species of shorebirds along the East Asian-Australasian Flyway have experienced rapid population declines over the years. Habitat loss and degradation in key stopover sites in the Yellow Sea regions are seen as the primary reasons.

However, many of the species seem to be disappearing faster than their critical stopover habitats, said Liang Dan, an associate research scholar at Princeton University in the United States.

"There are certainly other factors behind the declines," he said.

To gain a deeper understanding of the factors causing the population decline of the shorebirds and to take protective measures to mitigate or even reverse the declining trend, the Chinese conservation scientist and his team have been conducting a research project since August 2019 to assess the direct effect humans are having on the species.

"While designing the project during the start of my post-doctoral work at Princeton, I planned to focus the study on such direct threats as hunting or bycatch (fishing nets accidentally catching shorebirds) across China's coasts, which are only a part of the full flyway," Liang said, using the term to describe the flight path of the migratory shorebirds.

Liang and his team randomly chose 29 important stopover sites along the coasts to investigate in the autumn of 2019. They returned to all those sites in the spring of 2021 and made an alarming discovery.

In addition to hunting and bycatch, he and his team found a potentially serious threat previously unknown to scientists and conservationists — nets used to prevent shorebirds from foraging on young razor clams that are raised on the intertidal mud flats in southeastern China.

In April and May 2021, they estimated, the bird nets set up in Yueqing Bay in Zhejiang province and Xinghua Bay in Fujian province, covering an area of approximately 9 square kilometers, caused the deaths of about 14,000 migratory shorebirds.

The team also estimated the deaths of five species of shorebirds that were caught by the nets in large numbers — black-tailed godwit, terek sandpiper, common redshank, curlew sandpiper and sharp-tailed sandpiper.

The deaths of these birds made up close to or even exceeded 1 percent of their flyway populations, posing a significant threat to their global populations.

The study was conducted by Liang and a group of researchers and conservationists from China and the United States and was published recently in Conservation Biology, a journal issued by the Society for Conservation Biology.