Nest Box Condition and Maintenance of Barn Owls (Tyto alba) in Tropical Oil Palm Plantations

Barn owls (<i>Tyto alba</i>) are widely used as biological control agents in Southeast Asian agroecosystems, especially in oil palm plantations where rodent pests cause major yield losses. The success of such programs relies not only on nest box installation but also on maintaining the structural condition of these boxes. We analyzed monthly nest box monitoring data from January 2022 to May 2023 across five oil palm plantations (CPI1-CPI5) in Southern Thailand, including numbers of total, damaged, repaired, and unrepaired boxes. Substantial spatial variation was observed: CPI1 maintained the highest number of boxes (289) with a very low damage rate (~1.2%) and consistent repairs, whereas CPI4 showed the highest proportion of damaged boxes (~11%) and no repair activity. Chi-square and Kruskal-Wallis tests confirmed significant differences in damage rates among plantations (<i>p</i> < 0.001), although monthly variation was not statistically significant (<i>p</i> = 0.42). Visual inspection indicated increased deterioration during the wet season, suggesting weather-related stress on wooden structures. These results highlight the importance of maintaining nest box infrastructure as part of plantation management practices that support barn owl presence in oil palm agroecosystems. Keeping boxes functional throughout the year helps sustain a nature-based pest control service, reducing reliance on rodenticides and enhancing agroecosystem sustainability under humid tropical conditions.