There's a startling moment in the Lamentations of Jeremiah where he says:
Even the sea monsters draw out the breast, they give suck to their young ones: the daughter of my people is become cruel, like the ostriches in the wilderness.
Just as ostriches are now a byword for foolish cowardice, so they were once a byword for cruelty as they were believed to abandon their young. Either way, there must be something about those birds that we just don't trust.
There are lots of lovely bestial myths in the language like suicidal lemmings, disembarking rats (hence traitorous) and pacifist doves (as opposed to hawks). The sea monsters in that Biblical passage are pelicans*, which were believed to bite their own breasts when there was no food and let their young drink their blood. My favourite is that chameleons don't require food at all and survive on air, a belief that crops up in Hamlet:
Claudius: How fares our cousin Hamlet?
Hamlet: Excellent, i' faith; of the chameleon's dish: I eat the air, promise-crammed: you cannot feed capons so.
Claudius: I have nothing with this answer, Hamlet; these words are not mine
Hamlet: No, nor mine now.
The Inky Fool commuting to work
*As somebody is bound to point out, this seems to be a mistranslation in the King James Version and should really be jackals. However, the myth is true (if you see what I mean) nonetheless.