1, "call back" means call back, and "fly south" means fly south. This sentence tells us that we must follow the laws of nature, and everything should go with the flow and not be forced. Just like we have to let nature take its course in everything we do.

2. This sentence comes from the song "Half-life Snow", which was sung by Seventh Uncle (Ye Zehao) and included in the album "Half-life Snow".