Bird-watchers turn hobby into a citizen science

Tens of thousands are playing a key role in the research and conservation of China's migratory species, as Chen Liang reports

The north wind is blowing and autumn is coming. Many birds, especially water birds and raptors - or birds of prey - have started long-distance migrations from their breeding grounds to their wintering grounds.

From north to south, China is witnessing a massive annual movement of birds.