Living on the edge: range edge birds consume novel foods sooner than established ones

The ability to adjust behavioral responses to environmental cues probably contributes to an individual’s ability to persist in unfamiliar habitats. One behavior, how an individual responds to novelty, influences the acquisition of resources (e.g., novel foods) and identification of stressors, but it may also increase exposure to risks. Here, using house sparrows (Passer domesticus) recently introduced to Kenya, we tested how range expansion influenced individuals’ responses to novel foods and objects. We predicted that range edge birds would be less averse to novelty than birds at the site of introduction and that this effect would be more pronounced for novel foods than novel non-nutritional items. We also expected range edge individuals to be more sensitive to changes in the environment and therefore more apt to adjust their behavior in response to different cues; in other words, individuals at the range edge would have a more flexible behavioral repertoire than individuals at the site of introduction. As predicted, individuals at the range edge ate novel foods faster than those from established areas; however, latency to touch novel objects did not vary across the range. Individuals throughout the range were variable in their response to novelty, but there was no indication that individual flexibility was greater at the range edge. Although many novel items might be useful to introduced organisms, novel foods are likely more valuable, and therefore individuals should be most apt to risk the potential costs associated with novelty for a high nutritional payoff.