Habitat loss

"This, in turn, enables us to conduct research on their food resources and assess their general survival situations," Jia said.

They discovered that the Bohai Bay area was a major staging site for the cranes, where they would roost and feed for "at least one week and sometimes, as long as one month" during their migration from their breeding grounds to the wintering grounds. "Now, however, it has changed to the Shandian River Basin in Duolun, Inner Mongolia autonomous region," Jia said.

To discover the reason for the change, they analyzed the crane's historical habitats in the Bohai Bay area and identified a significant issue — habitat loss.

They examined various habitats such as grasslands, marshes, open water and farmlands to determine if they had been converted into other forms or developed for human use, such as urban areas or highways. Based on historical records and their observations, they found a loss of suitable habitats for the cranes at their historical staging site.

As a result, the birds had changed their migration route. "Some cranes were unable to adapt and disappeared, while others, more resilient and intelligent, relocated to the Shandian River Basin," Jia said.

Jia and his teammates have counted over 800 white-naped cranes in the area each year, and the estimated population is now around 1,000. "That means almost all birds of the western population will spend some time in the Shandian River Basin during their migration," he said.

He said the negative impact of habitat change on the cranes was obvious in Beijing's Miyun Reservoir area.