秃鹰摄食变化有利于物种延续
文章来源:未知 文章作者:meng 发布时间:2010-05-04 01:31 字体: [ ]  进入论坛
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An unprecedented1 study of bald eagle(秃鹰) diet, from about 20,000 to 30,000 years ago to the present, will provide wildlife managers with unique information for reintroducing(再引入,再提出) Bald Eagles to the Channel Islands off California. The scientists, including researchers from the Carnegie Institution's Geophysical Laboratory, found that eagles fed mainly on seabirds from about 20,000 to 30,000 years ago to the 1840s and 50s, when humans introduced sheep. The seabirds provided an abundant source of carrion2(腐肉,臭尸) for the local eagle population until the pesticide3 DDT wiped out the eagles in the 1960s. The results are published in the online early edition of the Proceedings4 of the National Academy of Sciences USA the week of May 3, 2010. "Reintroducing bald eagles to the Channel Islands has had mixed results," remarked lead author Seth Newsome, a postdoctoral researcher at Carnegie at the time of the study. "An understanding of their diet is critical to successful reintroduction, so we looked for chemical traces of the foods the eagles consumed over many millennia5(一千年) . Since bald eagles are extremely opportunistic(机会主义的) , they can quickly adapt to changes in the prey6 base of the diverse ecosystems7 they inhabit. Because there are no sheep on the islands today and the seabird populations are diminished, we think that the introduced eagles could scavenge(打扫,排除) seal or seal lion carrion, exert predation pressure(捕食压力) on a threatened but recovering local seabird population, or even prey on the endangered island fox."

"Each of these sources has its challenges for wildlife managers," Newsome continued. "Several studies have shown that seals and sea lions are contaminated(污染) with pollutants8, and a growing bald eagle population could potentially exert significant predation pressure on the fragile fox and seabird populations."

The scientists used a technique called stable isotope9(同位素) analysis of eagle bone and feather remains10 primarily from a historic nest on San Miguel Island that has been occupied for over 100 years before its abandonment in the mid-20th century. The also examined prehistoric11(陈旧的,史前的) material from paleontological(古生物学的) sites from the late Pleistocene on San Miguel Island and material collected during the historic period (1850-1950) from other Channel Islands and the southern California mainland.

Atoms of elements such as carbon and nitrogen, which cycle through the food chain, come in different forms, or isotopes12 that have the same number of protons(质子) , but different numbers of neutrons13. Scientists can distinguish them by the tiny differences in their masses.

As it turns out, marine14 and terrestrial(陆地的) prey have different amounts of the isotopes carbon-13 (13C) and nitrogen-15 (15N). The coastal15 marine ecosystems in California have higher amounts of 13C and 15N than adjacent(临近的,毗邻的) terrestrial ecosystems. The marine ecosystems also have more steps in the food chain than the terrestrial ecosystems, resulting in higher amounts of 15N. Since sheep and fox have different isotope ratios compared to seabirds and fish, the researchers could determine the diets of bald eagles by analyzing16 the isotopes found in their remains.



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1 unprecedented 7gSyJ     
adj.无前例的,新奇的
参考例句:
  • The air crash caused an unprecedented number of deaths.这次空难的死亡人数是空前的。
  • A flood of this sort is really unprecedented.这样大的洪水真是十年九不遇。
2 carrion gXFzu     
n.腐肉
参考例句:
  • A crow of bloodthirsty ants is attracted by the carrion.一群嗜血的蚂蚁被腐肉所吸引。
  • Vultures usually feed on carrion or roadkill.兀鹫通常以腐肉和公路上的死伤动物为食。
3 pesticide OMlxV     
n.杀虫剂,农药
参考例句:
  • The pesticide was spread over the vegetable plot.菜田里撒上了农药。
  • This pesticide is diluted with water and applied directly to the fields.这种杀虫剂用水稀释后直接施用在田里。
4 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
5 millennia 3DHxf     
n.一千年,千禧年
参考例句:
  • For two millennia, exogamy was a major transgression for Jews. 两千年来,异族通婚一直是犹太人的一大禁忌。
  • In the course of millennia, the dinosaurs died out. 在几千年的时间里,恐龙逐渐死绝了。
6 prey g1czH     
n.被掠食者,牺牲者,掠食;v.捕食,掠夺,折磨
参考例句:
  • Stronger animals prey on weaker ones.弱肉强食。
  • The lion was hunting for its prey.狮子在寻找猎物。
7 ecosystems 94cb0e40a815bea1157ac8aab9a5380d     
n.生态系统( ecosystem的名词复数 )
参考例句:
  • There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
  • Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样,从雨林到半荒漠等不一而足。 来自辞典例句
8 pollutants 694861490fe64672170a0da250a277c7     
污染物质(尤指工业废物)( pollutant的名词复数 )
参考例句:
  • Pollutants are constantly being released into the atmosphere. 污染物质正在不断地被排放到大气中去。
  • The 1987 Amendments limit 301(g) discharges to a few well-studied nonconventional pollutants. 1987年的修正案把第301条(g)的普通排放限制施加在一些认真研究过的几种非常规污染物上。 来自英汉非文学 - 环境法 - 环境法
9 isotope isotope     
n.同位素
参考例句:
  • The isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
  • How to apply a radio isotope?如何运用放射性同位素?
10 remains 1kMzTy     
n.剩余物,残留物;遗体,遗迹
参考例句:
  • He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
  • The remains of the meal were fed to the dog.残羹剩饭喂狗了。
11 prehistoric sPVxQ     
adj.(有记载的)历史以前的,史前的,古老的
参考例句:
  • They have found prehistoric remains.他们发现了史前遗迹。
  • It was rather like an exhibition of prehistoric electronic equipment.这儿倒像是在展览古老的电子设备。
12 isotopes 92848c3160703e48dc3b552ac6f54115     
n.同位素;同位素( isotope的名词复数 )
参考例句:
  • the many isotopes of carbon 碳的诸多同位素
  • Tritium is one of the mildest radioactive isotopes. 氚是最和缓的放射性同位素之一。 来自《简明英汉词典》
13 neutrons 8247a394cf7f4566ae93232e91c291b9     
n.中子( neutron的名词复数 )
参考例句:
  • The neutrons and protons form the core of the atom. 中子和质子构成了原子核。 来自《简明英汉词典》
  • When an atom of U235 is split,several neutrons are set free. 一个铀235原子分裂时,释放出几个中子。 来自《简明英汉词典》
14 marine 77Izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • When the war broke out,he volunteered for the Marine Corps.战争爆发时,他自愿参加了海军陆战队。
15 coastal WWiyh     
adj.海岸的,沿海的,沿岸的
参考例句:
  • The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
  • This country will fortify the coastal areas.该国将加强沿海地区的防御。
16 analyzing be408cc8d92ec310bb6260bc127c162b     
v.分析;分析( analyze的现在分词 );分解;解释;对…进行心理分析n.分析
参考例句:
  • Analyzing the date of some socialist countries presents even greater problem s. 分析某些社会主义国家的统计数据,暴露出的问题甚至更大。 来自辞典例句
  • He undoubtedly was not far off the mark in analyzing its predictions. 当然,他对其预测所作的分析倒也八九不离十。 来自辞典例句
TAG标签: diet wildlife eagle
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