This past summer, when I had just gotten six new baby chicks, I was astonished to hear one three-day old peep out the identical five-note phrase that I'd been used to hearing when the adult chickens noticed my cat approaching. The five notes are constant, except for a lilt or accent on the third note.
Just to make certain I wasn't imagining things, I later tried it with another baby. I called my cat into the room, and that chick immediately piped out the exact same five-note phrase with the accent on the third note. Peep-peep-PEEP-peep-peep!" (Here comes the cat!)
When I approach, they announce my presence with a similar five-note phrase, but there is NO accent, just five straight notes. "Bock-bock-bock-bock-bock!" (Here comes the human!")
It blew me away to discover that chickens, not only have language, but they have it from birth, and they have syntax! (Being able to form a phrase)
One rooster phrase I'd sure like to have translated for me goes: "nnnnnuh-YUH!" It seems to mean, "Don't mess with me!" At least when I repeat it back to him, he goes all ballistic. It's kind of fun pushing his buttons.
When I'm snuggling one of my lap hens in my arms, she will murmur, "Hmm-heh!". And I'll reply, "I love you, too!"