In Beijing in winter or early spring, passers-by may see groups of residents catching birds. Players blow plastic beads into the air through carbon tubes, allowing birds (usually from migrating sycamore species) to capture and return them in exchange for rewards. This is a tradition in Beijing that dates back to the Qing Dynasty, which ruled from the 17th to the early 20th century. Today, only about 50 to 60 people in Beijing are believed to still be practicing.