I do not understand the usage of "why" in this sentence. Here, this word seems to be used as "because". Is this some kind of archaism?
(Dr. Dolittle, emphasis added):
… You are the very first man to talk like us. Oh, sometimes people annoy me dreadfully—such airs they put on—talking about ‘the dumb animals.’ Dumb!—Huh! Why I knew a macaw once who could say ‘Good morning!’ in seven different ways without once opening his mouth. He could talk every language—and Greek …