A taste for novelty in invading house sparrows, Passer domesticus

One of the central questions in invasion biology involves why some introductions succeed and others fail. Although several correlates of invasion success have been identified, patterns alone cannot identify the mechanisms underlying the invasion process. Here, we test the hypothesis that one predictor of invasion success, behavioral flexibility, is different between invading and established populations of the same species of bird. We predicted that neophobia (fear of novelty), a surrogate of behavioral flexibility, would be weaker in an actively invading population (28 years resident; Colon, Republic of Panama) of house sparrows (Passer domesticus) compared to a population that had been resident for more than 150 years (Princeton, New Jersey, USA). To test this hypothesis, we compared latency to consume novel foods and phobia of novel objects between populations when both were kept under similar environmental conditions in captivity. As predicted, birds from the 150-year-old population took significantly longer to approach and consume novel foods than birds from the 28-year-old population. Responses to novel objects were not different between populations however; both populations fed more readily near some novel objects, which to our knowledge is the first such occurrence in a wild vertebrate species. Overall, a predilection for trying new foods and being attracted to novel objects may in part explain how this species has so successfully invaded new areas.