Avian diversity of rice fields in Southeast Asia

Abstract

The thesis investigated avian diversity within rice fields at three locations in the Philippines. From February 2012 until April 2014, avian community structure was recorded to determine the effect that different farming techniques have upon frequency and abundance within the habitat. Investigations were conducted to challenge the common misconception that all birds are a threat to crop yield, with detailed research into the life-cycle and diet of the Eurasian tree sparrow (Passer montanus). Twenty-seven continuous months of bird surveys were conducted to record annual, and temporal, changes in frequency and diversity. A total of 130 species were recorded, and explanations for abundance patterns discussed. Species biological richness scores indicated that time of year and field stage are important factors affecting diversity within rice fields. To investigate the effect different farming techniques have upon avian diversity, two largescale crop manipulations were investigated; fields under a water management technique (Alternate Wetting and Drying) and areas of accelerated rice production. Both investigations indicated that avian frequency and abundance were higher within manipulated fields when compared to control sites. Differences in community structure are discussed identifying a change under manipulated conditions. Artificial nest boxes were used to record breeding season and productivity, with biometric measurements, for the Eurasian tree sparrow sub-species‘saturatus’, which produced more eggs but successfully fledged fewer young, over a longer breeding period. A significant difference in wing formulae between sexes indicates a difference in life-style strategies. To determine diet, stable isotopic analysis of claws measured ratios of δ15N. Differences in δ15N were compared to a control group fed on a ‘pure’ diet. Results indicated a mixed diet when given free choice, but could not be identified within the current data set. Management strategies to reduce potential yield loss to birds, along with considerations for future work, are discussed