Phenotypic plasticity of avian social-learning strategies

Social learning, whereby animals learn from others, mediates the spread of information through social networks. To make this process adaptive, animals should be selective with respect to when and whom to copy. The cost of decision making can be curbed by cognitive biases favouring particular categories of individuals. Such model biases are well documented, but few, if any, experimental studies have addressed potential developmental causes of this variation. We therefore tested whether and how the postnatal environment affected social-learning preferences in a known social learner the zebra finch, Taeniopygia guttata. Birds from experimentally manipulated brood sizes, a treatment known to affect adult phenotypic quality in this species, were tested in an established observer–demonstrator paradigm. Naïve observers could watch unfamiliar same-sex conspecifics feed from differently coloured novel feeders. When subsequently allowed to choose between identical feeders, postnatal conditions (=rearing brood size) had strong effects on who copied whom in adulthood: males preferred the feeders of demonstrators from large brood sizes, females those of demonstrators from brood sizes matching their own, suggesting stratified information transfer within foraging groups. Our results demonstrate how individualsʹ developmental history can explain substantial interindividual variation in model biases and ensuing structured information transfer within groups.