Linking Dynamic Habitat Selection with Wading Bird Foraging Distributions across Resource Gradients: SFC Model

The spatial foraging conditions (SFC) models grouped foraging observations over time at a fixed cell and integrated spatial patterns (e.g., topography) unaccounted for by the chosen set of hydrological predictors (i.e., spatial correlation; Beerens et al, in press). By accounting for patterns in the spatial variation of the landscape, the noise independent of the hydrologic parameters can be reduced to better capture the species-specific behavioral response to rapidly changing habitat conditions (Dormann 2007). In addition to depth, recession, and DSD, the SFC used dry-to-wet reversal, and hydroperiod, averaged over each instance of cell use. The dry-to-wet reversal variable estimated when a cell had gone dry and rewet (within a dry season), which results in highly depleted fish populations (Trexler et al. 2002). Hydroperiod was defined as the 10-year mean in the annual length of cell inundation, which influences wading bird distributions through long-term changes in microtopography and vegetation communities. Frequency of cell use was defined as the number of times over the study period that a species used a given cell. Output from the SFC averaged over the landscape can serve as a surrogate measure of the abundance of high-quality patches.