Wild parrots exhibit age-dependent conformity when learning about novel food

There is extensive evidence that the spread of innovation via social learning can facilitate uptake of new foraging behaviours in populations. In comparison, social learning about novel food types has received comparatively little attention. Yet the adoption of novel food is vital to persistence in, or colonisation of, novel environments. Here, we present a novel food (almonds in the shell, coloured either blue or red) in a two-option and control cultural diffusion experiment to five neighbouring roosts of 705 individually-marked sulphur-crested cockatoos (Cacatua galerita) living in a highly urbanised environment. From 4 initially trained individuals, a total of 349 individuals across all roosts learned to feed on the novel food within 10 days of first exposure. Using network-based diffusion-analysis (N = 214 learners out of 322 individuals with available social information), we demonstrated that this spread occurred almost exclusively through social learning, with information spreading through social network ties. Second, using experience-weighted attraction models, we described age-differences in social learning strategies, with juveniles, but not adults, exhibiting a conformist bias to prefer the most frequently chosen food colour. Third, when analysing 539 opening techniques of the novel food by 147 individuals across the five roosts, we found that opening techniques were more similar between roost communities when the distance between sites was small, or the degree of movement between sites was high. In addition, when focusing on a subset for which social association data were available (273 openings by 78 individuals), techniques tended to be more similar between close associates. Taken together, our study suggests that the adoption of novel food in urban-living sulphur-crested cockatoos is facilitated by social transmission of knowledge through networks, with food choice further influenced in juveniles by a conformist learning bias. Social networks influenced both food choice and acquisition of foraging techniques within and between roosting communities, leading to differences at surprisingly local scales. The utilisation of new food resources is a fundamental component of adaptive behavioural responses to novel environments. Our study demonstrates how cognitive and social influences can be vital determinants of this adaptive flexibility.