Flocks of grey herons are photographed making nests in a forest in Guiyang, capital of Southwest China's Guizhou province, on April 20. [Photo/VCG]

Grain Rain, the last traditional solar term in spring, started on April 20, marking an end to the cold weather. On the same day, flocks of grey herons were photographed making nests in a forest in Guiyang, capital of Southwest China's Guizhou province.