Growth Period of Aquatic Plants for Birds Nesting at Bung Borapet, Nakhon Sawan

Abstract

Studies on the growth period of aquatic plants that were to be nested by birds was undertaken at Bung Borapet, Changwat Nakorn Sawan. It was found that the minimum densities of various plants for bird nesting were different and depended on nesting conditions. Salvinia cucullata Roxb., Potamogeton malaianus Miq. and Pheudoraphis spinescens Vickery with density of 267, 203 and 229 g m^-2 were used for nesting by Hydrophasianus chirurgus, respectively. While Porphyrio porphyrio, Porzana cinerea and Ixobrychus cinnamoneus preferred to nest over the water level, therefore, Eichhornia crassipes (Mart.) Solms, Pheudoraphis spinescens Vickery, Typha angustifolia L. and Nelumbo nucifera Gaerth with the densities of 1,050, 464, 4,133 an 886 g m^-2 were utilized, respectively. Growth period requirements of aquatic plants also differed accordingly to plant species and environmental factors. Pseudoraphis spinescens required the longest period of 11-15 months, whilst Potamogeton malaianus required the shortest period of 5 months. Whereas, Eichhornia crassipes, Nelumbo nucifera and Typha angustifolia required the period of 6 months, Salvinia cucullata required 7 months. The physical and chemical quality of the water obtained from Bung Borapet were found suitably for all common aquatic plants in the following ranges : depth of 135-345 cm, water transparency of 57-182 cm., temperature of 27.5-29.2 °C, DO of 2.9-5.2 mg/l, B.O.D. of 2.1-3.1 mg/l, alkalinity of 95.2-108.9 mg/l, pH of 7.2-7.8. The average amounts of base nutrient, nitrate, phosphate and potassium were 0.16, 0.01 and 3.9 mg/l, respectively. The ground-table soil was characterized as clay with the pH of 5.1 and 1% organic matter.