Passer domesticus

House Sparrows aggressively compete with native birds for food and nest sites and may reduce their nesting success. These invasive birds will use nest boxes intended for native birds and are known to evict other birds from nest sites, destroying eggs, killing nestlings, and sometimes killing incubating females. Male House Sparrows vigorously defend the area around their nests and may prevent other birds from nesting nearby. (Johnson, S.A. & Violett, H., 2012)

There was a dramatic decrease in the evenness of bird communities where House Sparrows were pres ent. This was caused by a reduction in bird species richness and an increase in bird abundances at invaded sites. Our results are consistent with patterns of diversity generated by other invasive species of different taxa, such as plants, invertebrates, and fishes (Vitousek et al. 1997; Gritti et al. 2006). The increase in total bird abundance at invaded sites was caused by a dramatic increase in the number of House Sparrow individuals. This is not surprising, since House Sparrows have been found to be a dominant species in the communities where they occur all over the world (Emlen 1974; Gavareski 1976; Cupul-Magan˜a 1996; Clergeau et al. 1998; White et al. 2005), and are an excellent example of an invasive urban exploiter species. The species turnover analysis at both scales showed that the bird composition of invaded and non-invaded sites was similar; however, invaded sites had low species richness due to the loss of several native species. Because our sampling sites for the small geographic-scale approach were environmen tally very similar, our results suggest that the presence of the House Sparrow is the cause of native species loss. This was supported by our results from the landscape-level approach, where regardless of environmental variation, invaded sites exhibited simpler, more dominated communities. One of the possible explanations for these patterns is the House Sparrow’s aggressiveness towards native species (Kalinoski 1975; Gowaty 1984). At our study sites we observed House Sparrows violently attacking some native species at feeding sites (e.g., Lesser Goldfinch, White-collared Seedeater, Golden-fronted Woodpecker). Similar aggressive interactions between the House Sparrow and local species have also been reported for other sites in North America (Kalinoski 1975; Grussing 1980; Gowaty 1984). (MacGregor-Fors, I. et al., 2009)