Flexible space use and activity budgets enable a rapidly growing waterbird population to track seasonal rice field dynamics

Abstract Agricultural expansion is a major driver of biodiversity loss, yet some species benefit from predictable resource pulses in anthropogenic habitats, a strategy that may require substantial behavioural adjustments. Rice fields provide abundant resources for waterbirds, but their management creates strong temporal variation in flooding, vegetation structure, and disturbance. We used GPS and tri-axial accelerometry from 39 glossy ibises ( Plegadis falcinellus ) to quantify reliance on rice fields and investigate how they adjust space use and activity budgets to track habitat dynamics across the pre-harvest, harvest, and post-harvest seasons. Glossy ibises relied strongly on rice fields throughout the study period but adjusted daily routines among seasons. Daytime use increased from ~ 60% in pre-harvest/harvest to ~ 95% in post-harvest. The lower use of rice fields during pre-harvest and harvest reflected individuals commuting to alternative habitats, especially intertidal mudflats, primarily for resting, consistent with avoidance of human disturbance. Daily travel distances peaked during harvest, whereas daily space-use areas were smallest during post-harvest. Foraging effort, measured as the daily proportion of time allocated to foraging behaviour, increased from 40% in pre-harvest/harvest to 67% in post-harvest, shifting from bimodal to sustained diurnal foraging. Short-term site fidelity was moderate and cumulative area used increased steadily across all seasons. These results show glossy ibises exploit a highly dyanamic agricultural system via moderate behavioural adjustments. Yet, increased rice reliance may heighten vulnerability to changes in agricultural practices, particularly reductions in flooding regimes.