由群集數量與取食速率探討樹麻雀(Passer montanus)於水稻田的取食模式

Abstract

Tree sparrow（Passer montanus）is a social animal. They would flock together and flew to the rice fields to forage on grain during rice ripening period result in the loss of production. Considering rice field in the background, understanding for foraging model of tree sparrow studied in this research. The main objective was to reduce the loss of production through the foraging model. We filmed the state of foraging of tree sparrows at the agricultural experimental station of National Chung-Hsing University at Taichung in Taiwan during February to June in 2008. Result detailed about the relationships between flock size and uptake rate through the food patch, where more individuals in a flock recorded lower alert frequency and forage faster. However, uptake rate is reduced due to the limited food supply. Therefore, the uptake rate of tree sparrows didn’t affected by flock size in the state of sufficient food supply. More individuals in one flock reduced the alert frequency and forage faster from foraging. In additional of food patch experiment, the rice grain weight measured every week from the rice heading stage. The data was calculated of flock size、foraging time and foraging frequency through the taped observation data, and combined the data with the result of food patch experiments to predict quantity of grains (kg/ha) did tree sparrows forage at organic rice field per day. The daily rice consumption (Y) and the mature date of rice(X) expresses as Y= 0.16X - 1.17 （R2 = 0.76, p<0.05）. The grains became heavier each day during the ripening period. Weight of the rice grain has changed during the ripening period, therefore, the number of grains consumed by tree sparrows represented the rice damage rate. Tree sparrow foraged the maximum on the fourth week of rice ripening period with an average of fifty-eight percent of all foraging amount. According to this study, the foraging amount of first-crop rice of tree sparrows in 2009 is 206.2 kg with equivalent to one percent of total rice yield. In addition, the damage rate is the most concerning is 0.49％, on the fourth week. We quantified the damage of foraging amount of tree sparrows. The tree sparrows foraged more and more when the ripening progresses. Therefore, current research concluded to take damage control action from the day of 21 to 28 after the rice heading, as it was the time of most serious damage by tree sparrow foraging.