What is "zhenniao"

Zhenniao or sometimes translated as Zhen or Poisonfeather Birds, is a name given to poisonous birds that is said to have existed in what is now present-day Southern China during ancient times and is referenced in many Chinese myths, annals and poetry. The Shanhaijing Chapter 5: Classic of the Mountains: Central describes the Zhen as resembling an eagle living in Girl's Tabletop Mountain, Lutemute Mountain and Jade Mountain in Southern China.