Avifaunal diversity associated with Bentota river mangrove, Southwestern Sri Lanka: Implications for conservation

Abstract

Sri Lanka is a tropical country with mangrove cover found in most of its coastal zone, bordering lagoons, estuaries, and protected bays. Mangroves consist of rich biodiversity that provides habitats for numerous species. The Bentota River, located in the Galle District in the Southern Province, has a well-developed riverine mangrove forest. It adds biological and ecological values to this highly populated area. The present study focuses on enumerating the avifaunal diversity associated with Bentota riverine mangrove forest. A three-month survey from April to June 2021 was conducted in 500 m long transects to assess the avifaunal diversity. The Shannon Index (H), Shannon Evenness (E), and the Simpson’s Index (D) were calculated. A total of 1,629 individuals of 69 species belonging to 30 families were recorded from the area. The Shannon Index, Shannon Evenness and Simpsons’ Index were 3.69, 0.875, and 0.0318, respectively. Thus, the area represents considerable avifaunal diversity including six endemic birds; Crimson-fronted Barbet (Megalaima rubricapillus), Sri Lanka Green Pigeon (Treron pompadora), Sri Lanka Hanging Parrot (Loriculus beryllinus), Sri Lanka Jungle Fowl (Gallus lafayettii), Yellow-fronted Barbet (Megalaima flavifrons) and Sri Lanka Swallow (Cecropis hyperythra). Waterbirds recorded include White-breasted Waterhen (Amaurornis phoenicurus), Lesser Whistling Duck (Dendrocygna javanica), Common Kingfisher (Alcedo atthis), White-throated Kingfisher (Halcyon smyrnensis), Black-headed Ibis (Threskiornis melanocephalus) and Slaty-legged Crake (Rallina eurizonoides), a rare nationally threatened (Critically Endangered) waterbird. Several threats viz., habitat destruction by clearing mangroves, garbage dumping, and spreading invasive Annona glabra and Dillenia suffruticosa were recorded. Therefore, proper law enforcement, together with conservation measures, is recommended to protect this sensitive habitat.