A common merganser. [Photo by Dong Si/tidenews.com.cn]

Dong Si, vice-chair of the Zhejiang Wild Bird Society and captain of the West Lake mandarin duck conservation team, announced the arrival of the common merganser at Hangzhou's West Lake on Dec 15, meaning that all four of the area's iconic winter migratory bird species have now arrived.

Spotted early this morning near Yongjin Gate, the lone male merganser leisurely swam and dove in the lake, signaling the start of their seasonal migration. As in past years, more mergansers are expected to join in the coming days, with the winter population typically stabilizing at eight to 10 birds.

West Lake's winter migratory visitors include cormorants, mandarin ducks, vega gulls, and common mergansers. These species will overwinter in Hangzhou before returning north in spring to breed.

The birds' arrival times vary by species. Cormorants, the earliest visitors, are usually spotted as early as mid-September, while mandarin ducks appear in early November. Black-headed gulls follow in late November, and the common mergansers arrive in December. Departure patterns also differ: latecomers like mergansers typically leave after Chinese New Year, while cormorants linger until April.

In recent years, West Lake has recorded over 60 bird species wintering or resting in the area. Popular observation spots include the music fountain and the stretch between Dahua Hotel and Long Bridge Park.