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We do not know how vocal learning came to be, but it is such a salient trait in human evolution that many have tried to imagine it. In primates this is difficult because we are the only species known to possess this skill. Songbirds provide a richer and independent set of data. I use comparative data and ask broad questions: How does vocal learning emerge during ontogeny? In what contexts? What are its benefits? How did it evolve from unlearned vocal signals? How was brain anatomy altered to enable vocal learning? What is the relation of vocal learning to adult neurogenesis? No one has described yet a circuit or set of circuits that can master vocal learning, but this knowledge may soon be within reach. Moreover, as we uncover how birds encode their learned song, we may also come closer to understanding how we encode our thoughts. (Contains 8 figures.)

Given the difficulty of following free-living, dispersing juvenile songbirds, relatively little is known about when, where, how, and from whom these young birds learn their songs. To explore these issues, we studied the Chipping Sparrow (Spizella passerina), males of which have a single, simple song, but populations of which may contain 20-30 different songs. In our western Massachusetts study sites, we color-banded 324 nestling and 32 fledgling sparrows. Twelve of these banded males returned to our study areas, dispersing a few hundred meters to 1.8 km away from their natal territories. The song of each yearling closely matched only one of his immediate neighbors on the breeding territory, revealing that a yearling sparrow precisely imitates one of his close neighbors after dispersal. Evidence from this field study and a previous laboratory study show that a young male is able to learn songs either during his hatching year or the following spring, perhaps depending on his chances of song exposure or social interaction with territorial neighbors. Key words: Chipping Sparrow, instructive learning, selective learning, song learning, song sharing, Spizella passerina. Dada la dificultad de seguir a juveniles de aves canoras que se dispersan en ambientes naturales, se sabe muy poco acerca de cuando, donde, como y de quien estas aves juveniles aprenden sus cantos. Para explorar estas preguntas, estudiamos machos de Spizella passerina, los cuales tienen un canto unico y simple, pero que provienen de poblaciones que pueden tener 20 a 30 cantos diferentes. En nuestros sitios de estudio en el oeste de Massachusetts anillamos 324 polluelos y 32 volantones con bandas de colores. Doce de estos machos anillados volvieron a nuestros sitios de estudio, dispersandose desde sus territorios natales entre unos cuantos cientos de metros a 1.8 km. El canto de cada juvenil de un ano solo coincidio con el canto de uno de sus vecinos mas cercanos en el territorio de cria, lo cual revela que los juveniles de un ano imitan de manera precisa el canto de uno de sus vecinos mas cercanos luego de dispersarse. Evidencias de este estudio de campo y otros estudios previos de laboratorio muestran que un macho joven es capaz de aprender cantos tanto durante el ano que eclosiono como durante la primavera siguiente, quizas dependiendo de sus probabilidades de exposicion al canto o de interacciones sociales con sus vecinos territoriales.

Does the ontogeny of vocal imitation follow a set program that, given a target sound, unfolds in a predictable manner, or is it more like problem solving, with many possible solutions? We report that juvenile male zebra finches, Taeniopygia guttata, can master their imitation of the same song in various ways; these developmental trajectories are sensitive to the social setting in which the bird grows up. A variety of vocal developmental trajectories have also been described in infants. Are these many ways to learn unique to the vocal domain or a hallmark of advanced brain function? learning strategy | social influence | vocal learning | zebra finch

A survey of the design of animal behaviour 'Playback' experiments published during the last few years, focusing on pseudoreplication issues, is presented.