Understanding the sources of variation in the cognitive abilities in wild populations is a fundamental question in cognitive ecology. Developmental conditions can be one such source, but little is known about its role in wild populations. We tested whether variation in development is associated with differences in performance in a spatial learning and memory task and in a reversal spatial learning task using wild food-caching mountain chickadees across different montane elevations over 3 years. We assessed developmental stress by measuring corticosterone, length and mass in an outer tail feather grown during early development in juvenile birds sampled in mild (low elevation) and harsh (high elevation) environments. We tested spatial cognitive abilities in these birds in 2 spatial tasks using our RFID-based design. Considering that the feather represents conditions over the entire developmental period, rather than a single point, these methods allow us to test whether variation in overall developmental condition is associated with differences in spatial cognitive abilities.

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