Neophobia, aversion to open space, and ecological plasticity in Song and Swamp sparrows

Abstract

The Song Sparrow (Melospiza melodia) is a habitat generalist and successful colonist of habitats altered by man and of small islands. The Swamp Sparrow (Melospiza georgiana) is more restricted in its habitat distribution, occurring primarily in marsh or marsh-like habitats. In field experiments I examined the role of certain aversions in shaping the apparent difference in ecological plasticity found in these species. I tested for differences in aversion to feeding in the presence of novel objects and away from cover and found that such conditions greatly reduced the visitation rate of Swamp Sparrows but not Song Sparrows to feeding stations. I found no differences between the species in the degree to which feeding rate, visit length, or group size changed between areas with and without cover. Neither did I find a difference in feeding behavior or flight speed in the two species. I suggest that the increased hesitancy that Swamp Sparrows show for foraging away from cover or at novel objects reflects selection to reduce exploratory behavior away from preferred habitat types in this more stereotyped species.