Seasonal Flooding Effects on Reproductive Success Nesting Patterns and Juvenile Survival of Aquatic Bird Species

Abstract

Background: Seasonal flooding is a natural hydrological activity of floodplain and wetland ecosystems that significantly influences the ecological behaviors of aquatic birds with reproductive behaviors. Mechanistic relationships between the surge period, magnitude, and period of floods and nesting success and juvenile survival are however yet to be fully described across tropical floodplain bird assemblage. Purpose: The paper was research into seasonal flooding impacts on the reproductive success, nest-site selection, and clutch size, hatching rates and juvenile survival of five aquatic species in the floodplain wetlands of Vembanad Kol Ramsar Site, Kerala, India. Techniques: Two full annual flood cycles (20232024) were systematically monitored via transect and analysis of predefined nest localities, GPS-tagged nest mapping, and camera trapping of 180 active nests. Water-level gauges and Sentinel-1 SAR satellite images gave the depth, duration, and the date of inundation at 14-day intervals. Another method of survival tracking of the juveniles was by colour-banding of 312 chicks and resighting. Findings: Early flooding (> 28 days preceding mean nest initiation day) diminished the success of the clutch by 43.6 percent in comparison with late years of floods. The highest adaptive plasticity was found in purple heron (Ardea purpurea), which just about regained its nest within 18 days after the flood had receded. In low-flood years, overall juvenile survival to fledging was 52.4 percent, whereas, in high-flood years, it was 31.7 percent (2 = 14.82, p < 0.001). Conclusion: Flood phenology is one of the main predictors of the reproductive performances of floodplain aquatic birds. The preservation of the natural flood pulsing and regulation of the occurrence of the extreme inundations are crucial in supporting the population of waterbirds in the controlled wetland environment.