Defining nest site microhabitats and preferences to aid in the recovery of the Cape Sable seaside sparrow

Lockwood, Julie; Fenn, Katherine; Warren, Tara; Hirsch-Jacobson, Robin; Van Holt, Arnaud; Fargue, Agnes

To bridge the gap between existing fine and coarse-scale breeding habitat information, we gathered nest -site microhabitat data collected across the sub-species' current range. We make a special effort to integrate our results with those of Werner (1975) as his report is by far the most comprehensive study to date but is not readily accessible. Protecting habitats that provide suitable breeding habitat is critical for the recovery of endangered birds. Thus far, managers have been inhibited in protecting appropriate habitats for the endangered Cape Sable seaside sparrow because most of the sparrow's range lies within inaccessible regions of the everglades ecosystem. From 1997-1999 we collected microhabitat variables around 110 sparrow nests located across the sub-species' range. We can identify only two microhabitat variables that differ between nest sites located in spatial distinct regions of the sparrow's range, or sub-populations. These are a decrease in dominance of muhly grass outside of the most accessible sub-population (B) and a decrease in the degree of vegetative clumping within the western-most subpopulation (A). This indicates that Cape Sable seaside sparrows have a relatively 'fixed' preference for nest site vegetative structure. When we compared nest site microhabitats to available, but unused, microhabitats within territories we identified a suite of vegetative cues sparrows use for nest placement. In particular, this includes a moderately high dominance of sawgrass. The presence of saw grass (dead and alive) contribute preferred structural characteristics such as high ground cover, high vegetation heights (used as perching substrate), moderately high coverage of dead vegetation and vegetative clumping. These results provide managers with a better understanding of the habitat requirements of breeding Cape Sable seaside sparrows. What remains to tested, however, is how variations in these preferred habitat characters influence nest predation and thus annual productivity.