Biodiversity Assessment of Paddy Field Ecosystem using Birds as a Biodiversity Indicator

Biodiversity assessment is considered in making decisions concerning declaration ofprotected areas, management of nature reserves and assessment of the success ofmanagement decisions within a particular area. Biodiversity indicators are used as measuresof biodiversity. Degree of disturbance or fragmentation of a definite habitat can be measuredusing specific indicator species. A variety of invertebrates and vertebrates are widely used asindicators of biodiversity. Birds are one of the best species for the national and internationalbiodiversity schemes to be used as a biodiversity indicator.This study focused on the use of birds as an ecological indicator to assess the paddy fieldecosystem. The study was carried out in a minor irrigation system in Awlegama AgrarianService area in Wariyapola Divisional Secretariat. Bayawa was the selected tank with nearlya 38 ha of command area. A standard fixed-radius point count method with the radius set at25 m was used to sample birds in the paddy field ecosystem. Shanon index was used toexplain the results. During a single rice cycle, rice plants undergo three main phenologicalstages namely; vegetative, reproductive and ripening. All these stages are influenced byfarming practices such as tillage, irrigation, crop establishment, agrochemical application andweeding. Different stages with different farming practices create distinct habitats for variousbird species. According to the results, the highest Shanon index value (highest diversity) wasrecorded during the vegetative stage. Birds‟ diversity had a significant, strong (p=0.05)negative correlation with the age of the paddy. Initial land preparation and vegetative stagesprovide more food sources for the predatory birds who feed on worms, insects and snails;some of whom act as pests of paddy. Mixing of upper and the sub-soil layers in landpreparation stages supply more feed for predatory birds. Cattle Egret, Red Wattled Lapwing,Intermediate Egrets, Indian Pond Heron, Black Necked Stroke were in abundance at landpreparation and vegetative stage. Yellow crowned woodpecker and White throated muniawere recorded during the later stages. A variety of management practices such as landpreparation, crop establishments, irrigation, nutrient and pest management, harvesting withinthe paddy field facilitate to create different habitats with different eco systems and suitablefood for bird species. The birds as a biodiversity indicator, symbolise the ecosystem and itreflects the existing condition of an ecosystems. A detailed study will reveal how these birdswould help to manage different pests in the paddy fields to bring benefits to the farmers.Keywords: Biodiversity indicator, Ecosystem, Paddy field, Birds, Cattle Egre