Ackerman Joshua T, Eagles-Smith Collin A, Takekawa John Y, Bluso Jill D, Adelsbach Terrence L
US Geological Survey, Western Ecological Research Center, Davis Field Station, One Shields Avenue, University of California, Davis, California 95616, USA.
Environ Toxicol Chem. 2008 Apr;27(4):897-908. doi: 10.1897/07-230.1.
We examined mercury concentrations and space use of prebreeding Forster's terns (Sterna forsteri) in San Francisco Bay, California, USA, to assess factors influencing mercury levels in piscivorous birds. In 2005 and 2006, we collected blood and feathers from 122 Forster's terns and radio-marked and tracked 72 terns to determine locations of dietary mercury uptake. Capture site and capture date were the most important factors explaining variation in blood mercury concentrations (geometric mean +/- standard error: 1.09+/-0.89 microg/g wet wt), followed by sex and year. Accordingly, radiotelemetry data revealed that Forster's terns generally remained near their site of capture and foraged in nearby salt ponds, managed and tidal marshes, and tidal flats. In contrast, capture site and capture date were not important factors explaining variation in feather mercury concentrations, probably because feathers were grown on their wintering grounds several months prior to our sampling. Instead, sex and year were the most important factors explaining mercury concentrations in breast feathers (9.57+/-8.23 microg/g fresh wt), and sex was the most important factor for head feathers (6.94+/-7.04 microg/g fresh wt). Overall, 13 and 22% of prebreeding Forster's terns were estimated to be at high risk for deleterious effects due to mercury concentrations in blood (>3.0 microg/g wet wt) and feathers (>20.0 microg/g fresh wt), respectively. Breeding terns are likely to be even more at risk because blood mercury concentrations more than tripled during the 45-d prebreeding time period. These data illustrate the importance of space use and tissue type in interpreting mercury concentrations in birds.
我们研究了美国加利福尼亚州旧金山湾繁殖前期的弗氏燕鸥（Sterna forsteri）的汞浓度和空间利用情况，以评估影响食鱼鸟类汞含量的因素。2005年和2006年，我们从122只弗氏燕鸥身上采集了血液和羽毛，并对72只燕鸥进行了无线电标记和追踪，以确定膳食汞摄入的位置。捕获地点和捕获日期是解释血液汞浓度变化的最重要因素（几何平均值±标准误差：1.09±0.89微克/克湿重），其次是性别和年份。因此，无线电遥测数据显示，弗氏燕鸥通常停留在捕获地点附近，并在附近的盐池、人工管理和潮汐沼泽以及潮滩觅食。相比之下，捕获地点和捕获日期不是解释羽毛汞浓度变化的重要因素，可能是因为羽毛是在我们采样前几个月在它们的越冬地生长的。相反，性别和年份是解释胸羽汞浓度的最重要因素（9.57±8.23微克/克鲜重），而性别是解释头羽汞浓度的最重要因素（6.94±7.04微克/克鲜重）。总体而言，估计分别有13%和22%的繁殖前期弗氏燕鸥因血液（>3.0微克/克湿重）和羽毛（>20.0微克/克鲜重）中的汞浓度而面临有害影响的高风险。繁殖期的燕鸥可能面临更高的风险，因为在45天的繁殖前期，血液汞浓度增加了两倍多。这些数据说明了空间利用和组织类型在解释鸟类汞浓度方面的重要性。
