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

Abstract

Biodiversity assessment is considered in making decisions concerning declaration of
protected areas, management of nature reserves and assessment of the success of
management decisions within a particular area. Biodiversity indicators are used as measures
of biodiversity. Degree of disturbance or fragmentation of a definite habitat can be measured
using specific indicator species. A variety of invertebrates and vertebrates are widely used as
indicators of biodiversity. Birds are one of the best species for the national and international
biodiversity schemes to be used as a biodiversity indicator.

This study focused on the use of birds as an ecological indicator to assess the paddy field
ecosystem. The study was carried out in a minor irrigation system in Awlegama Agrarian
Service area in Wariyapola Divisional Secretariat. Bayawa was the selected tank with nearly
a 38 ha of command area. A standard fixed-radius point count method with the radius set at
25 m was used to sample birds in the paddy field ecosystem. Shanon index was used to
explain the results. During a single rice cycle, rice plants undergo three main phenological
stages namely; vegetative, reproductive and ripening. All these stages are influenced by
farming practices such as tillage, irrigation, crop establishment, agrochemical application and
weeding. Different stages with different farming practices create distinct habitats for various
bird species. According to the results, the highest Shanon index value (highest diversity) was
recorded 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 stages
provide 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 land
preparation stages supply more feed for predatory birds. Cattle Egret, Red Wattled Lapwing,
Intermediate Egrets, Indian Pond Heron, Black Necked Stroke were in abundance at land
preparation and vegetative stage. Yellow crowned woodpecker and White throated munia
were recorded during the later stages. A variety of management practices such as land
preparation, crop establishments, irrigation, nutrient and pest management, harvesting within
the paddy field facilitate to create different habitats with different eco systems and suitable
food for bird species. The birds as a biodiversity indicator, symbolise the ecosystem and it
reflects the existing condition of an ecosystems. A detailed study will reveal how these birds
would help to manage different pests in the paddy fields to bring benefits to the farmers.

Keywords: Biodiversity indicator, Ecosystem, Paddy field, Birds, Cattle Egret