Stable Isotope Analysis Reveals That Agricultural Habitat Provides an Important Dietary Component for Nonbreeding Dunlin

Although shorebirds spending the winter in temperate areas frequently use estuarine and supratidal (upland) feeding habitats, the relative contribution of each habitat to individual diets has not been directly quantified. We quantified the proportional use that Calidris alpina pacifica (Dunlin) made of estuarine vs. terrestrial farmland resources on the Fraser River Delta, British Columbia, using stable isotope analysis (δ13C, δ15N) of blood from 268 Dunlin over four winters, 1997 through 2000. We tested for individual, age, sex, morphological, seasonal, and weather-related differences in dietary sources. Based on single- (δ13C) and dual-isotope mixing models, the agricultural habitat contributed approximately 38% of Dunlin diet averaged over four winters, with the balance from intertidal flats. However, there was a wide variation among individuals in the extent of agricultural feeding, ranging from about 1% to 95% of diet. Younger birds had a significantly higher terrestrial contribution to diet (43%) than did adults (35%). We estimated that 6% of adults and 13% of juveniles were obtaining at least 75% of their diet from terrestrial sources. The isotope data provided no evidence for sex or overall body size effects on the proportion of diet that is terrestrial in origin. The use of agricultural habitat by Dunlin peaked in early January. Adult Dunlin obtained a greater proportion of their diet terrestrially during periods of lower temperatures and high precipitation, whereas no such relationship existed for juveniles. Seasonal variation in the use of agricultural habitat suggests that it is used more during energetically stressful periods. The terrestrial farmland zone appears to be consistently important as a habitat for juveniles, but for adults it may provide an alternative feeding site used as a buffer against starvation during periods of extreme weather. Loss or reduction of agricultural habitat adjacent to estuaries may negatively impact shorebird fitness, with juveniles disproportionately affected.

黑腹滨鹬亚种分类研究进展

黑腹滨鹬Calidris alpina因繁殖季节其腹部有黑斑而得名,是北半球最常见的鸻形目鸟类之一.黑腹滨鹬历史上共命名过11个亚种,经过2次主要的系统厘定后,目前认为分化有10个亚种.亚种间除在量度性状、体色性状和地理分布有区别外,还在换羽模式、线粒体谱系组成等方面有所不同,从而使其成为研究种群分化的理想对象之一.本文介绍了黑腹滨鹬的亚种分类性状、分类修订以及亚种分类系统,并就非繁殖期的相关研究作了概述.由于混群,非繁殖地的亚种鉴定与繁殖地的亚种鉴定在性状的使用侧重上有很大的不同.非繁殖地亚种的划分,以环志回收结果和线粒体DNA谱系组成为主,其它性状为辅.中国究竟有几个亚种分布还需要进一步研究后才能确定.