Using Distance Sampling to Estimate Population Density of Eastern Great Egret (Ardea alba modesta) in North-Central Selangor Coast, Malaysia

Abstract

The most recent East Asian-Australasian Flyway Conservation Status Review in 2022 revealed that there are insufficient data available for population size estimates for the Eastern Great Egret (Ardea alba modesta) in Asia. The conservation status of the Eastern Great Egret has remained unknown since the decimation of its largest colony in Pulau Tengah within North-Central Selangor Coast, an Important Bird and Biodiversity Area (IBA) in Malaysia. Understanding the population status and density distribution of the Eastern Great Egret is crucial for informed wildlife ecology and wetland management. This study represents the first attempt to obtain baseline absolute population density for this species by applying distance sampling along the entire coastline of the North-Central Selangor Coast. The intertidal mudflat of the coast was backed by mangrove forest (125.25 km2), and the sub-coastal agricultural areas (185.40 km2) were surveyed with 130-point count stations placed randomly within the landscape. The total population estimated was 15,448 individuals with 14,863 (96.2%, 119 individuals/km2) estimated in coastal habitat and 585 (3.8%, 4 individuals/km2) estimated in paddy fields. The results show that distance sampling is a viable monitoring technique for estimating absolute population densities of waterbirds in a heterogenous landscape like North-Central Selangor Coast.