To send a letter from afar; to correspond with someone. This idiom refers to a legend about a wild goose carrying a message tied to its leg while the envoy [[苏武|蘇武|su1 wu3]] was held captive by the [[匈奴|匈奴|xiong1 nu2]].

A pigeon trained to carry messages or mail; carrier pigeon; messenger pigeon

To send a letter or stay in touch via mail; this idiom originates from a legend where the Han official [[苏武|蘇武|su1 wu3]] used a wild goose to carry a message back home while he was being held captive