春江水暖鴨先知 [－－－－鸭－－]

Jyutping ceon1 gong1 seoi2 nyun5 aap3 sin1 zi1
Pinyin chūn jiāng shuǐ nuǎn yā xiān zhī

Definitions (CC-CEDICT)
  1. lit. the duck is the first to know if the spring water is warm (idiom)
  2. fig. an expert in the field knows which way the wind blows
Definitions (Wiktionary)
  1. proverb
    Professionals within an industry or profession will be the first to notice a change in circumstances.