Variation in avian responses to rice intensification in the central plains of Thailand guides conservation opportunities

Abstract

Multiple studies indicate that grassland and farmland birds are declining in temperate zones, but few have been conducted in the tropics. Here we examined effects of rice intensification on landbird communities and estimated habitat-specific densities of eight songbird species of national and/or global conservation concern in the central plains of Thailand where rice is intensively cultivated often with triple annual rice crops. From 1410 point-counts, we observed 236 species including 26 landbirds of conservation concern. The landbird species community was significantly associated with different intensification levels, with eleven species of concern primarily found in single-cropped fields. Three of the eight focal species (i.e., Horsfield's bushlark Mirafra javanica, Oriental skylark Alauda gulgula, and striated grassbird Megalurus palustris) had lower densities with increased intensification. Natural habitat features (i.e., field margins, reedbeds, and scattered trees) positively influenced densities of all species, even those unaffected by intensification. Densities of Manchurian reed warbler Acrocephalus tangorum, streaked weaver Ploceus manyar, and Asian golden weaver P. hypoxanthus were positively correlated with increases in field margins and reedbeds. Plain-backed sparrow Passer flaveolus density was positively related to presence of scattered trees. Long-tailed shrike Lanius schach density appeared to have a positive correlation with field margins and was significantly negatively correlated with urbanization. Our findings underscore the necessity of adopting policies that encourage wildlife-friendly land management in Southeast Asia, reducing intensification of agricultural landscapes that support species of conservation concern and preserving natural habitat features. Long-term population monitoring is also needed to better understand trends and judge management efficacy.