Adapting foraging to habitat heterogeneity and climate change: an individual-based model for wading birds

Abstract

In an effort to assess the role of adaptive foraging behaviour to the spatial and temporal heterogeneity as a factor determining the success of the colony, we used single-colony individual-based spatial models for a visual foraging, the Great Blue Heron and a tactile foraging bird, the Wood Stork. The model followed simultaneously daily activities of individuals, their spatial movements, foraging efficiency, bioenergetics and growth of the nestlings during a nesting season. For each colony we used two scenarios; in the first, that depicted a normal nesting season, the extent and distribution of feeding sites led to successful reproduction for both species. In the second, we simulated increased precipitation regimes resulting in reversals in water depth (i.e. increases in depth during the dry season when water levels are normally falling). The results reveal that Wood Storks were significantly more adversely affected than Great Blue Herons by the prey dilution caused by the reversals in water depth. In the latter scenario where resources became scarce, resource predictability decreased. The foraging birds that foraged in groups exhibited low foraging success, resulting in poor reproductive performance. This result was more pronounced in the case of storks that foraged in groups than for herons foraging in groups. Concluding, increased variance in precipitation regimes is more likely to affect tactile rather than visual foraging bird species. Further, in harsh climatic conditions (increased precipitation and water level regimes) solitary foraging was more beneficial for wading birds than group foraging.