The return of duck to Hong Kong after a year-long 6,000km (3,700-mile) journey to the Arctic has yielded new information about bird migration.
The female, fitted with a tracking device, was one of about 20 monitored by the WWF conservation group.
Using Google Earth, the WWF identified the duck's feeding areas and route back to Hong Kong's Mai Po Nature Reserve.
Another duck flew at the record-breaking speed of 114km/h (70mph), the data revealed.
The Mai Po Nature Reserve's manager, Bena Smith, said the duck that returned often travelled at 50km/h (31mph).
One of the birds was shot dead over Russia, where its transmitter was tracked to what was probably the hunter's home.
WWF and its partners, including the US Geological Survey, are studying not only migration but also avian diseases.