The Wildlife Institute of India (WII) has found that water availability is the single most critical factor determining when colonial waterbirds begin breeding, how large their colonies grow, and how many species a wetland can sustain. The findings, published on 21 October 2026, carry significant implications for wetland conservation policy across monsoon-dependent landscapes in southern India.

Key Findings of the Study

Conducted across nine wetlands in Tamil Nadu over three consecutive breeding seasons from 2022–2023 to 2024–2025, the study documented 16 colonial nesting waterbird species and identified wetland water extent as the strongest predictor of nesting occurrence, colony abundance, and species richness. The research combined systematic field surveys, Sentinel-2 satellite imagery, and climate data from the ERA5 reanalysis dataset.

Greater inundation was consistently associated with a higher probability of colony establishment, larger breeding aggregations, and greater species diversity. Notably, environmental conditions during the 30 days preceding surveys provided the strongest explanatory power for breeding responses — underscoring the importance of near-term hydrological conditions over longer-term climate averages.

Role of Climate Variables

While water extent emerged as the dominant driver, the study also examined the influence of temperature, precipitation, and wind speed using generalised linear mixed models. Maximum temperature negatively affected both colony abundance and species richness. Precipitation exerted a weaker negative effect, and wind speed showed no statistically significant impact. The findings confirm that climatic factors play a secondary, rather than primary, role in shaping breeding dynamics.

What WII Recommends

The institute, an autonomous body under the Ministry of Environment, Forest, and Climate Change (MoEFCC), has called for a paradigm shift in conservation planning. 'Conservation planning must move beyond individual wetland boundaries. Conservation strategies should prioritise the maintenance of adequate water levels during breeding seasons through effective management of reservoirs, irrigation systems and canal networks supplying water to such biodiverse-rich wetlands,' the WII stated.

This comes amid increasing climatic variability that threatens the hydrological stability of monsoon-dependent wetlands — ecosystems that researchers describe as highly sensitive to environmental fluctuations but poorly understood in terms of what drives colonial waterbird breeding within them.

Research Support and Broader Context

The study was supported by the Anusandhan National Research Foundation (ANRF), Government of India. Researchers emphasised the importance of integrating hydrological monitoring, climate information, and long-term ecological surveys to strengthen conservation frameworks. This is among the first studies to rigorously quantify the relative contribution of inundation versus climate variables to waterbird breeding dynamics across multiple wetlands over multiple seasons in tropical India, lending it particular methodological weight.

With wetlands under mounting pressure from agricultural water diversion, groundwater depletion, and erratic monsoon patterns, the study offers conservation managers a data-backed basis for prioritising water-level management as a frontline tool for protecting colonial waterbird populations.