Abstract

Rice paddy-fields have become increasingly important worldwide as reliable alternative foraging sites for many wading birds due to the rapid loss or degradation of their natural wetland habitats. While assemblage and dispersal patterns of these birds are influenced by spatial distribution of their food resources, foraging activities of some species contribute significantly to natural suppression of some organism harmful to agriculture or human health. This 4-month study investigated how paddy-field management practices influence spatial and temporal linkage between African Openbill Stork distribution and abundance to that of its gastropod mollusc prey resources at Ahero Rice Irrigation Scheme, western Kenya. Regression models predicted African Openbill Stork abundance's positive response to gastropod prey abundance, but negative response to conspecific competition abundance. Stork abundance also increased in response to rice-crop stage, with highest abundances at mid-crop stages, though only marginally due to field-flooding. Contrarily, gastropod abundance increased progressively with rice-crop phases, peaking at transplanting before reducing to stabilization towards crop maturity and harvesting. Paddy-field-block size showed no effect on abundances either Openbill Stork or gastropods. However, paddy block size predicted positive effect on Openbill Stork abundance when interacted with rice growth stage, and with gastropod abundance. Conversely, abundance of competing waterbirds, when interacted with gastropod abundance or rice-crop stage, predicted lower stork abundance, reaffirming negative impact of conspecific competition for stork assemblage. The findings demonstrate the significant role of gastropod food resources in overall distribution and assemblage of African Openbill Stork, impact of conspecific competition, and the crucial indirect influence of anthropogenic field management in shaping these dynamics through agronomic practices especially field flooding control and rice production cycles generally. The results are applicable in designing rice-fields as attractive alternative habitats for Openbill Stork and other waterbirds, to harness their potential contribution to bio-regulating the gastropod vectors of schistosomiasis.