Raptor Research Center at Boise State University, Minden, NV 89423, USA.
Ecotoxicology. 2010 Jan;19(1):153-62. doi: 10.1007/s10646-009-0400-8. Epub 2009 Aug 21.
Locations of contaminant exposure for nesting migratory species are difficult to fully understand because of possible additional sources encountered during migration or on the wintering grounds. A portion of the migratory white-faced ibis (Plegadis chihi) nesting at Carson Lake, Nevada continues to be exposed to dichloro-diphenyldichloro-ethylene (DDE) with no change, which is unusual, observed in egg concentrations between 1985 and 2000. About 45-63% of the earliest nesting segment shows reduced reproductive success correlated with elevated egg concentrations of >4 microg/g wet weight (ww). Local prey (primarily earthworms) near nests contained little DDE so we tracked the migration and wintering movements of 20 adult males during 2000-2004 to determine the possible source. At various wintering sites, we found a correlation (r (2) = 0.518, P = 0.0125, N = 11) between DDE in earthworm composites and DDE in blood plasma of white-faced ibis wintering there, although the plasma was collected on their breeding grounds soon after arrival. The main source of DDE was wintering areas in the Mexicali Valley of Baja California Norte, Mexico, and probably the adjacent Imperial Valley, California, USA. This unusual continuing DDE problem for white-faced ibis is associated with: the long-term persistence in soil of DDE; the earthworms' ability to bioconcentrate DDE from soil; the proclivity of white-faced ibis to feed on earthworms in agricultural fields; the species's extreme sensitivity to DDE in their eggs; and perhaps its life history strategy of being a "capital breeder". We suggest surveying and sampling white-faced ibis eggs at nesting colonies, especially at Carson Lake, to monitor the continuing influence of DDE.
筑巢的迁徙物种的污染物暴露地点很难完全了解，因为在迁徙过程中或在越冬地可能会遇到其他额外的来源。在内华达州卡森湖筑巢的部分迁徙白脸琵鹭（Plegadis chihi）继续接触二氯二苯二氯乙烯（DDE），其浓度在 1985 年至 2000 年之间没有变化，这很不寻常。大约 45-63%的最早筑巢段显示出繁殖成功率降低，与升高的 >4μg/g 湿重（ww）的卵浓度相关。巢附近的当地猎物（主要是蚯蚓）中 DDE 含量很少，因此我们跟踪了 20 只成年雄性在 2000-2004 年期间的迁徙和越冬运动，以确定可能的来源。在不同的越冬地点，我们发现白脸琵鹭越冬地的蚯蚓混合物和血液等离子体中的 DDE 之间存在相关性（r (2) = 0.518，P = 0.0125，N = 11），尽管血浆是在它们到达后不久在繁殖地收集的。DDE 的主要来源是墨西哥下加利福尼亚州诺特的墨西卡利谷和可能相邻的加利福尼亚州帝国谷的越冬地。白脸琵鹭持续存在 DDE 问题与以下因素有关：DDE 在土壤中的长期持久性；蚯蚓从土壤中生物浓缩 DDE 的能力；白脸琵鹭在农田中食用蚯蚓的倾向；该物种对卵中 DDE 的极度敏感性；以及其作为“资本繁殖者”的生活史策略。我们建议在筑巢地，特别是在内华达州卡森湖，对白脸琵鹭卵进行调查和采样，以监测 DDE 的持续影响。
