活动背景秃鼻乌鸦是北京地区的常见鸟,1956年11月中旬在女三中院内,有2000多只栖息。1961年11月8—12月7日平均每小时见到234只秃鼻乌鸦,一棵树上聚集百只以上,归宿时排粪如雨,顷刻间覆满地表。1973年中国科学院动物研究所普查秃鼻乌鸦时仅见40余只。90年代以后在城区基本见不到秃鼻乌鸦了。由于人类的经济活动和生活条件的改善,对环境也造成一定影响,使某些 Background Bald nosed crow is a common bird in Beijing. In mid-November 1956, there were more than 2000 inhabitants in the Third Women’s Third Intermediate Hospital. From November 8 to December 7, 1961, an average of 234 bald crows were seen every hour on average. One hundred or more birds were gathered in one tree. 1973 Chinese Academy of Sciences Institute of Zoology survey of bald crows only see more than 40 only. After the 90s in the city basically can not see bald crows. Due to the improvement of human economic activities and living conditions, it has also had an impact on the environment so that certain