Dialects are one of the parallels that have long been established between human language and animal communication. Here we will describe the different forms of “dialects” discovered in animals and discuss some potential functional parallels between human and animal dialects, arguing that in both cases different mechanisms and functions may be at stake where large geographical versus very localized (e.g. social) variations are concerned. Birdsong studies in particular, but also recent studies of mammal vocalizations, show that the use of the term “dialect” to refer to within-species vocal variations in animal species is more than a metaphor and that animal dialects offer a possibility to explore the causes and functions of linguistic variation and change. We present here an original view, as our approach is not “primate-centered”, and takes into consideration “homoplasy” (analogy) as a potential mechanism to explain that different taxa have evolved the same functional response to social constraints. We will develop an integrative view of animal dialects through birdsong studies where ontogeny, causality (brain processes), functions and evolution are considered in a common framework.