Ayup mi duck is a common way to say hello in the area of the British Midlands where I was born and raised, roughly translated as ‘hello friend, may your tribe exponentially increase’.

Have any of you ever witnessed or engaged in similarly fowl greetings?

No. But I've heard from a friend about a man who said “urgh, urgh, jag skulle vilja ha en kopölsa, kultat i flött, hackade gurka å en juicapööööse!” which is a very funny way of saying “I like a hotdog and a soft drink please” even for someone who speak swedish as their native language^^

People really do say “G'day mate” in australia…
Granted, by people I mostly just mean me.