Ducks say: "Quack"
Dogs say: "Ruff"
Cats say: "Meow"
Cows say: "Moo"...
Now having stated that...
Humans have been given the capacity to say so much more, to create and speak so many languages and dialects, and to think, understand, and communicate, in so many developed, intelligent, unlimited ways. That capacity is quite awesome in itself; and, when we compare those capabilities to the animals... well, of course - it's astonishing!
The great difference being: animals are given (shall we say) - an automatic language, which is set (unless there is a horse, that is related to "Mr. Ed"... just kidding); while humans have a language that is quite versatile, and changing. Our capacity to verbally/vocally choose our expressions/what we say, and to communicate our thoughts, feelings, and emotions - the way that we are able to, is really (quite) something to rave about.
Have you ever wondered about when "Mother Nature" was handing-out the involuntary/automatic animal languages... how did she choose which animal, went with which language - (if you will)?