Bergmann F B, Amaral H L C, Pinto D P, Chivittz C C, Tozetti A M
Programa de Pós-graduação em Biologia de Ambientes Aquáticos Continentais, Laboratório de Ecologia de Vertebrados Terrestres, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, CEP 96201-900, Rio Grande, RS, Brazil.
Braz J Biol. 2013 May;73(2):245-52. doi: 10.1590/S1519-69842013000200004.
The snail kite (Rostrhamus sociabilis) is widely distributed in the American continent. Its specialised diet consists mostly of the gastropod mollusk Pomacea sp and its foraging strategy probably varies depending on the season, prey availability, and climate factors, which can be reflected in its semi-nomad behaviour. This study was aimed at examining the hunting strategy of the snail kite, and its association with climate factors and habitat heterogeneity. Direct observations of birds between January 2010 and March 2011 in southernmost Brazil revealed that hunting was still the predominant foraging strategy (79% of records) to capture mollusks. Despite morphological specialisations to extract mollusks from the shells, the handling time (average = 92.4 s) was twice as much the time between prey search and capture (average = 55 s). The increase in the number of mollusks ingested apparently occurs when the resting time on perches or any other substrates near the hunting sites decreases between successive unsuccessful attempts. The correlation between the number of consumed preys and the climatic variables examined was low. Regarding habitat heterogeneity, our findings suggest that birds forage preferentially in marshes with low vegetation, which may increase the access to mollusks. The hunting efficiency of the snail kite was high (76 % successful attempts) compared to those of other birds of prey.
蜗牛鸢（Rostrhamus sociabilis）广泛分布于美洲大陆。其特殊的食性主要由腹足纲软体动物福寿螺构成，并且其觅食策略可能会因季节、猎物可获得性和气候因素而有所不同，这可以从其半游牧行为中体现出来。本研究旨在探究蜗牛鸢的捕猎策略，以及它与气候因素和栖息地异质性之间的关联。2010年1月至2011年3月在巴西南部对鸟类的直接观察表明，捕猎仍然是捕获软体动物的主要觅食策略（记录的79%）。尽管在从壳中取出软体动物方面具有形态学上的特殊性，但处理时间（平均 = 92.4秒）是猎物搜索和捕获之间时间（平均 = 55秒）的两倍。在连续的不成功尝试之间，当在捕猎地点附近的栖木或任何其他基质上的休息时间减少时，摄入的软体动物数量明显增加。所消耗猎物数量与所研究的气候变量之间的相关性较低。关于栖息地异质性，我们的研究结果表明，鸟类优先在植被较低的沼泽地觅食，这可能会增加获取软体动物的机会。与其他猛禽相比，蜗牛鸢的捕猎效率较高（成功尝试的比例为76%）。
