The hoopoo: "He that shows no mercy, shall not obtain mercy.".    From Wordnik.com.  [The Child and Childhood in Folk-Thought Studies of the Activities and Influences of the Child Among Primitive Peoples, Their Analogues and Survivals in the Civilization of To-Day] Reference

Man to start for the pampas of Patagonia to hunt the hoopoo.    From Wordnik.com.  [The Hohenzollerns in America] Reference

As for hoopoe, I will quote The Century Dictionary, definition and all, with its abbreviations expanded: "The form hoopoe was doubtless originally pronounced like hoopoo, which, with hoophoop, first appears about 1667-78; an imitative variant or clipped reduplication of the earlier hoop, apparently after Latin upaupa ….    From Wordnik.com.  [OUPblog] Reference

The birds are the blackbird, a black mina, the house-sparrow, sparrow-hawk, larger crow, domestic pigeons, kites, and hoopoo.    From Wordnik.com.  [Journals of Travels in Assam, Burma, Bhootan, Afghanistan and the Neighbouring Countries] Reference