Swiftlets (Aerodramus spp.) that produce edible bird’s nests (EBN) are flying insectivores and have economic value. Swiftlet houses for harvesting EBN have been constructed to sell EBN in Palangka Raya, Kalimantan Island, Indonesia. However, swiftlet houses are constructed without consideration of ecological impacts, and may lead to heavy impacts on foraging behavior and human-induced expansion of habitats. For this reason, it is essential to understand the food resources and surrounding environment of the swiftlet house sites before construction for the sustainable development of the EBN industry.
Therefore, we considered that it is necessary for the residents who will construct the swiftlet houses to understand the condition of food resources near new houses. In this study, we investigated the swiftlet food resources and environmental conditions in wetlands through the citizen science based field survey, and verified whether the survey method is appropriate and the most suitable season for conducting this survey. In addition, we evaluated the optimal survey season through satellite image analysis using Google Earth Engine.
The field survey focused on approximately 130 wetland sites within a 3 km radius of University of Palangka Raya, Kalimantan Island. Wetland sites were identified through satellite image interpretation before the field survey. The field survey was conducted with four groups of three to four members each, in September 2024. The participants were not necessarily ecology majors. They qualitatively recorded information about the wetland sites, such as the abundance of insects and swiftlets, color and odor of the water, turbidity, floats and other environmental conditions, through direct observation. Before the field survey, all participants piloted the same sites to confirm criteria and methods. To determine the optimal survey season, we calculated the Normalized Difference Water Index (NDWI), which is used to detect water bodies, for the wetland sites where water was observed. We used Sentinel-2 imagery in Google Earth Engine and then we compared the NDWI values in the early dry season and the mid-to-late dry season.
The results suggest that it is possible to evaluate the swiftlet food resources and environmental conditions through this survey approach. The optimal survey season is proposed to be the mid-to-late dry season. Furthermore, additional research is needed to compare these results with quantitative research and weather conditions.