Cezilly F, Boy V, Hafner H
Station biologique de la Tour du Valat, Le Sambuc, 13200 Arles, France.
Behav Processes. 1990 Jun;21(2-3):69-80. doi: 10.1016/0376-6357(90)90016-9.
Results from both field and experimental foraging studies of little egrets (Egretta garzetta) are used to discuss the relationship between flocking, prey density and foraging efficiency. In the field, the latter was affected by group size. The two parameters studied, striking efficiency (percentage of successful pecks) and the number of captures per minute improved in large groups. On the other hand, only in one of two field sites did the results reveal an improvement under the form of a reduced variance in striking efficiency, of birds in a small group as compared to solitary birds. During the experiments, the number of captures per minute was higher in a pool with high prey density than in situation with low prey density, while differences were not significant when comparing medium with low or high prey density. Group size had no effect on capture rate. Striking efficiency, searching effort and prey selectivity were not affected by flocking or prey density. The possible benefits of flock feeding are discussed.
小白鹭（Egretta garzetta）的野外觅食研究和实验觅食研究结果被用于探讨群居、猎物密度与觅食效率之间的关系。在野外，觅食效率受群体大小影响。所研究的两个参数，即啄击成功率（成功啄击的百分比）和每分钟捕获量，在大群体中有所提高。另一方面，仅在两个野外地点中的一个，结果显示小群体中的鸟类与单独觅食的鸟类相比，啄击成功率的方差有所降低，呈现出一种改善。在实验中，猎物密度高的水池中每分钟捕获量高于猎物密度低的情况，而将中等猎物密度与低或高猎物密度进行比较时，差异不显著。群体大小对捕获率没有影响。啄击成功率、搜索努力和猎物选择性不受群居或猎物密度的影响。文中讨论了群体觅食可能带来的益处。
