 They may also benefit from the increased group interaction on the level of cognitive concern for one another increasing their overall life span and survival.Approximately eight percent of bird species are known to regularly engage in cooperative breeding, mainly among the Coraciiformes, Piciformes, basal Passeri and Sylvioidea.Only a small fraction of these, for instance the Australian mudnesters, Australo-Papuan babblers and ground hornbills, are however absolutely "obligately" cooperative and cannot fledge young without helpers.