Foraging behavior of Brazilian cormorant, Nannopterum brasilianus (Suliformes: Phalacrocoracidae)

ABSTRACT Although the concept of optimal foraging has been extensively discussed, foraging efficiency is difficult to assess in vertebrates. In this study, we determined the foraging efficiency of the Brazilian cormorant, Nannopterum brasilianus Gmelin, 1789, by the direct, ad libitum observation of a group of four to thirteen individuals in an artificial pond at the University of São Paulo, Piracicaba, state of São Paulo, southeastern Brazil. Although this study was carried out in a highly anthropic environment, we can still conclude that the Brazilian cormorant is a relatively efficient browser and short-term diver. In anthropic environments, foraging success depends on the amount of time these birds spend diving, and stealing food is less common. Stealing occurs at relatively low rates but tends to be an efficient way to get food.

摘要 尽管最优觅食理论（optimal foraging）已得到广泛探讨，但针对脊椎动物的觅食效率评估仍存在较大难度。本研究于巴西东南部圣保罗州皮拉西卡巴市的圣保罗大学人工池塘内，对由4至13只个体组成的群体开展直接自由取样观察，以此测定巴西鸬鹚（*Nannopterum brasilianus* Gmelin, 1789）的觅食效率。尽管本研究在高度人工化的环境中开展，但仍可得出结论：巴西鸬鹚属于觅食效率相对较高的巡游觅食者与短时潜水者。在人工化环境中，此类鸟类的觅食成功率取决于其潜水时长，盗食行为的发生频率较低。尽管盗食行为的发生比例相对偏低，但其仍是一种高效的食物获取方式。