Neurogenesis in adult brains was widely thought to be a specialization of lower vertebrates related to life-long changes in body size. In mammals, it was accepted that neurogenesis is restricted to the olfactory epithelium, despite early reports of neurogenesis in the rodent hippocampus. This dogma of rare adult neurogenesis was further challenged by the work of Goldman and Nottebohm (1983), who described extensive neurogenesis in the brain of adult canaries, a songbird species. Since then it has become obvious that adult neurogenesis is a general feature of the forebrain and hippocampus of birds and that adult neurogenesis also occurs in various mammalian brain areas such as the hippocampus, the striatum, and the cortex, even in primates and humans. Thus, besides anatomical and biochemical plasticity of permanent neurons and neuronal networks, the loss and addition of neurons in adulthood might be a major adaptive mechanism used by vertebrates to cope with changing environments. Alternatively, neurogenesis might be a repair strategy to maintain neural networks. The present paper examines the functional relevance of adult neurogenesis.We focus on birds since most hypotheses on the functional role of adult neurogenesis have been put forward within the realm of the vocal and food-storing behaviors of birds.