Baiyangdian Lake in Hebei province, which includes northern China's largest freshwater wetland, has become a paradise for birds, including some rare ones, since its water quality improved greatly in the past several years.

Birds have returned in great numbers. A total of 237 species currently inhabit the wetland, 31 more than the time before Xiong'an New Area was built, Hebei Daily reported.

The birds include the Baer's Pochard, a critically endangered species of diving duck that was spotted in the wetland about four months ago. The diving ducks have also reproduced.

The new area was established in 2017 to advance the coordinated development of the Beijing-Tianjin-Hebei region. Baiyangdian covers about 360 square kilometers with 143 small lakes.

In 2018, water in the lake was rated at or below Grade V — the worst level in the country's five-tier quality system for surface water.

With pollution-control measures and environmental management of the lake in place, water quality reached Grade III last year, according to the department of ecology and environment in Xiong'an.

To provide a healthy habitat for the birds, the wetland has laid out nine sections as special roosts, with enhanced protection and management.