Using Spatial Point-Pattern Assessment to Understand the Social and Environmental Mechanisms That Drive Avian Habitat Selection

[摘要] Understanding when species distributions should be ascribed to patterns in the physical habitat, rather than to the influence of social cues, is a crucial step in understanding avian habitat selection. To distinguish between these mechanisms, we assessed the point pattern of 213 Saltmarsh Sparrow (Ammodramus caudacutus) nests and the spatial autocorrelation of vegetation characteristics at two study sites. Our tests of aggregation at cumulative and discrete distance classes failed to detect any significant nonrandom pattern, which is consistent with the hypothesis that nest placement is random with respect to other nests. When the timing of nesting attempts was taken into account such that only previous or currently active nests were considered, there was still no evidence that females attempted to nest closer to other nests than expected given random site selection. The underlying spatial structure of the vegetation variables was somewhat patchy, but not in a way that was consistent between sites or that matched patterns in nest placement, which suggests that female Saltmarsh Sparrows do not distribute themselves within marshes according to these features. A lack of association between vegetation characteristics and the probability of nest flooding, which is the primary source of nest failure in this species, may explain the apparent lack of spatial structure.

[学科分类] 动物科学

[关键词] Ammodramus caudacutus;conspecific attraction;nest aggregation;pair correlation function;Ripley's K function;Saltmarsh Sparrow;spatial autocorrelation