Ecological functions of parrots: an integrative perspective from plant life cycle to ecosystem functioning

Parrots (Psittaciformes) have been viewed as efficient consumers of the reproductive structures of plants. Consequently, parrots have been excluded from studies focusing on plant–animal mutualistic relationships as they have been considered only as plant antagonists. This prevailing view is challenged, however, by recent studies showing that (1) several parrot species are the main seed dispersers of some plant species through stomatochory; (2) the proportion of seeds removed and dispersed to long distances is high in some plant–parrot systems; (3) seeds dispersed by parrots are able to produce seedlings, even in some cases after being partially consumed; (4) tiny seeds are also legitimately dispersed by parrots through endozoochory; (5) seeds dropped by parrots under the mother tree can be consumed and secondarily dispersed by a variety of other species; and (6) parrots can also pollinate and heal their food plants by consuming their parasites. Through both antagonistic and mutualistic interactions with their food plants, parrots can exert cascading effects on the plants’ life cycles and shape the structure and functioning of ecosystems. The later was evaluated by a few studies showing how parrots may shape vegetal landscapes by influencing the spatial distribution and demography of their food plants and vegetal communities. On the other hand, mutualistic interactions lead to an increase of the parrot community robustness when facing the loss of plant species. We provide guidance for further research on the multiple plant–parrot interactions, also encouraging the assessment of how the ongoing decline and extirpation of parrot populations may cause regional losses of key ecological functions.