Sun Chin, Ives Anthony R, Kraeuter Hans J, Moermond Timothy C
Department of Zoology, University of Wisconsin-Madison, Madison, WI 53706, USA, , , , , , US.
Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI 53706, USA, , , , , , US.
Oecologia. 1997 Sep;112(1):94-103. doi: 10.1007/s004420050288.
We studied the effectiveness of three species of turacos, the Great Blue Turaco, the Ruwenzori Turaco, and the Black-billed Turaco, as seed dispersers in a tropical forest in Rwanda. For each species of turaco, we examined two factors affecting the effectiveness of seed dispersal: (1) the proportion of ingested seeds dispersed away from the parent tree and (2) the distances seeds were dispersed. To estimate these measures of effectiveness, we systematically observed the foraging activities of focal birds over a 14-month period. We also fed six species of tree fruits to captive Ruwenzori Turacos to determine the gut retention times for seeds of various sizes. Based on these measures, we calculated the seed shadows generated by each turaco species for tree seeds with either long or short gut retention times. The gut retention time of seeds was not correlated with seed size, but was positively correlated with the time interval over which seeds were defecated. Seeds with a long gut retention time were not only dispersed farther away from the parent tree, but were also deposited over a longer time period and were thus likely to be dispersed over a greater variety of habitats. Of the three turacos, the Ruwenzori Turaco deposited the highest percentage of ingested seeds away from the parent tree because it had the shortest residence time in feeding trees. However, the Ruwenzori Turaco also dispersed seeds for the shortest distance, partly due to its short flight distances. The Great Blue Turaco on average dispersed seeds the farthest due to its long flight distance and long gut retention time. The Black-billed Turaco, which fed least frequently, deposited seeds more evenly among perching sites than did the other two species. All three species of turacos dispersed over 80% of ingested seeds away from the parent tree.
我们研究了三种蕉鹃，即大蓝蕉鹃、鲁文佐里蕉鹃和黑嘴蕉鹃，作为卢旺达一片热带森林中种子传播者的有效性。对于每种蕉鹃，我们考察了影响种子传播有效性的两个因素：（1）摄入的种子中远离母树传播的比例，以及（2）种子传播的距离。为了估算这些有效性指标，我们在14个月的时间里系统地观察了焦点鸟类的觅食活动。我们还将六种树果投喂给圈养的鲁文佐里蕉鹃，以确定不同大小种子的肠道保留时间。基于这些指标，我们计算了每种蕉鹃对肠道保留时间长或短的树木种子产生的种子扩散阴影。种子的肠道保留时间与种子大小无关，但与种子排便的时间间隔呈正相关。肠道保留时间长的种子不仅传播得离母树更远，而且沉积时间更长，因此可能传播到更多样化的栖息地。在这三种蕉鹃中，鲁文佐里蕉鹃将摄入种子中最高比例的种子传播到远离母树的地方，因为它在采食树上停留的时间最短。然而，鲁文佐里蕉鹃传播种子的距离也最短，部分原因是其飞行距离较短。大蓝蕉鹃由于飞行距离长和肠道保留时间长，平均传播种子的距离最远。黑嘴蕉鹃采食频率最低，与其他两个物种相比，它在栖息地点之间更均匀地沉积种子。所有三种蕉鹃都将超过80%摄入的种子传播到远离母树的地方。
