Foraging Site Selection by Nonbreeding White-Faced IBIS

We examined foraging site selection by White-faced Ibis (Plegadis chihi) wintering in the Grasslands Ecological Area, which contains the second largest population of nonbreeding ibis in California. We compared habitat variables at White-faced Ibis foraging sites with paired, random locations in managed wetlands of the Grasslands. We contrasted the density and biomass of benthic macroinvertebrates between a subsample of bird foraging locations and random sites. Compared to random locations, the foraging locations of White-faced Ibis were closer to emergent vegetation > 10 cm in height. Moreover, ibis selected foraging locations with significantly higher chironomid and lower oligochaete biomasses relative to random sites. These findings suggest that ibis foraged close to vegetation where prey abundance may be greater and illustrate the importance of maintaining the presence of emergent vegetation in freshwater wetlands.