LAUSR

Variations in the factors affecting prey availability directly impact on the spatial dispersion of foraging birds. The feeding success and efficiency of the Black-headed Heron (Ardea melanocephala) was examined in the different growth stages/phases of paddy rice, namely: Ploughed fields, Phase 1 fields (2 weeks-1 month after sowing) and Harvested fields. Feeding success of the Black-headed Heron varied significantly across the rice growth stage. This variation was explained by a combination of factors such water depth, waterbird abundance, Nearest Neighbor Distance (NND) and food or prey abundance (except amphibian abundance). Statistical analysis were conducted using Genstat Version 8.1 (VSN Intl.2003, in which a General Linear Mixed Model were used to examine the variation in each behavioural measure. Foraging in aggregations on rice paddies seems to be more beneficial to the Black-headed Heron. The closeness to a conspecific had a positive effect on the feeding efficiency of the Black-headed Heron as they foraged on fields with abundant prey (Phase 1) and a negative effect on fields with less abundant prey (Ploughed fields). Generally, the data seem to suggest that there is a functional relationship between the Black-headed Heron, and prey abundance, and the absence of interference competition on rice fields.