They absolutely do. Besides the obvious clucking that may denote danger or announcing an egg has been laid, they have definite, easily discerned phrases. And it would appear they're born knowing this language and speak it right away! This was a complete gob-smack five weeks ago when I had just gotten a new batch of six baby chicks. I was holding one tiny three-day-old in my lap when my cat strolled into the room. The chick had been chirping steadily up until it spied the cat. Out came a perfect five note phrase from her teensy self that was exactly like the five note phrase clucked by the older chickens whenever the cat appears. Has anyone ever tuned into the various chicken phrases? The phrase for "here comes the cat" is a steady five notes with the accent on the third note. When I approach the chickens, their phrase for "here comes the human" is a perfect five note phrase with no accent on any of the notes. Thinking this was an aberration, I put that baby back and got another one out of the brooder. I walked into the other room where the cat was and the chick whistled the exact same five note phrase as the other baby! Over the five weeks that the chicks have been in the house in their brooder, there have been countless times to verify this example of language in baby chicks. Every single time that the cat appears while I'm holding a chick, or even when I'm just transporting them in the pet carrier outdoors to their pen, if they see the cat, one or two will announce it with that exact five note phrase with the accent on the third note! We all are aware chickens have a language of sorts to communicate with each other. But the spectacular revelation is that they're born knowing language! And even more spectacular, we can understand it given patience and mindfulness.