What are the competitive effects of invasive species? Forty years of the Eurasian collared-dove in North America

Abstract

Eurasian collared-doves (Streptopelia decaocto; hereafter ‘collared-doves’) have spread throughout North America since they first colonized Florida in the early 1980s. Here I test for adverse effects of this introduced species on four confamilial potential competitor dove and pigeon species using data from the breeding season (North American Breeding Bird Survey; BBS) and the winter (Audubon Christmas Bird Count; CBC). Within sites of both sets of surveys, correlations between populations of collared-doves and all four potential competitor species have generally been either nonsignificant or positive, indicating a lack of adverse competitive effects due to collared-doves. Similarly, there were no significant differences in population trends of any of the four species in sites where collared-doves were present compared to those where they were not, and there have been no significant declines in population trends of the four species driven by differences in collared-dove abundance in areas where the latter were present. Overall, analyses revealed no negative effects of collared-doves on populations of these potential competitors. Evidence thus far supports a ‘passenger’ rather than a ‘driver’ role for collared-doves in North America, although future monitoring of potential competitor species is warranted, especially if collared-dove populations continue to increase.