Social play in kaka (Nestor meridionalis) with comparisons to kea (Nestor notabilis)

AbstractSocial play in the kaka (Nestor meridionalis), a New Zealand parrot, is described and contrasted with that of its closest relative, the kea (Nestor notabilis), in one of the first comparative studies of social play in closely related birds. Most play action patterns were clearly homologous in these two species, though some contrasts in the form of specific play behaviors, such as kicking or biting, could be attributed to morphological differences. Social play in kakas is briefer, more predictable, and less sequentially diverse than that shown by keas. Kaka play also appears to be restricted to fledglings and juveniles, while the behavior is more broadly distributed among age groups in keas. Play initiation behaviors were relatively more frequent in kakas and more tightly intercorrelated in occurrence. A primary grouping of action patterns in kakas consisted of arboreal play, which was rare in keas. The most striking species difference was exhibited in social object play, which is pervasive among keas, but which was not observed in kakas. Although the two species are morphologically similar, they differ strikingly in several aspects of their ecology and social behavior, including the duration of the association between juveniles and adults, the degree of exploratory behavior, and the flexibility of their foraging strategies. The observed species differences in play behavior are discussed in relation to the contrasting life histories in the two species, suggesting that many features of social play may reflect evolutionary responses to particular ontogenetic and ecological constraints.