专家：死鸟死鱼没有异常情况

伤我心太深 · 发表于 2011-1-7 12:46:09

天落死鸟并无异常

本周野生动物们可没什么好日子过。

就在新年来临的开始，500 只红翼鸫在路易斯安那州集体死亡。大约 100 只穴乌在瑞典街头死亡。而在阿肯色州，估计有 100000 条鱼翻了白肚皮，而第二天有 5000 只画眉全速撞死在屋顶、邮箱和地面上。

像这样大规模、戏剧性且高姿态的事件引发了人们对大自然开始走到临头的担忧，或者至少是有什么怪异而不安的事情在动物王国中发生了。

但专家表示，像这样的大规模死亡并非不正常。

野生动物健康专家表示，从蝙蝠到鲸鱼再到蜜蜂和青蛙，每年都会由于包括恶劣天气、疾病暴发和中毒等原因发生重大死亡事件。而最近这次连续事件似乎非常奇怪，因为大部分时候，大规模死亡都发生在没有人会注意到的角落。

“这确实不是人们渲染的那样不同寻常的事情，”加州大学戴维斯分校的禽流生态学家 Robert Meese 所。“有许多这样的事情会发生，而没有人记录下来。”

大规模死亡在以大群落聚集或迁徙的动物中间最为常见。

例如候鸟常常由于大雾或者风暴而迷失方向，导致它们撞向高塔、桥梁、风轮机和树木。在它们漫长的路途中，候鸟们也可能意外地吞下杀虫剂或甚至是专为它们设下的毒药。天气也可能与它们作对，特别是如果它们在异常寒冷的年份中过早地迁徙。

丹佛美国地质勘查局的发言人 Marisa Lubeck 说，由美国地质勘查局保留的记录列出了过去 30 年中至少 16 次超过 1000 只画眉或星椋鸟大规模死亡的事件。但动物中的集体死亡事件在之前就早已有之了。

在 2007 年《朱鹭》杂志发表的回顾性研究中，研究人员查阅了回溯到 19 世纪后期的欧洲和北美洲鸟类期刊和其他的参考文献。他们发现频繁出现成百上千甚至更多鸟类死亡的报导。

在其中最极端的一个案例中，估计有 150 万拉普兰铁爪鸟死于明尼苏达州和爱荷华州在 1904 年 3 月的一场风暴中。

而且并非只有鸟类才会大规模死亡。成千上万的大马哈鱼在 2002 年死于北加利福尼亚洲的克拉马斯河中，当时河水温度对它们而言过高了。

鲸鱼、海豹和海龟的搁浅事件时常引起我们的注意。在近年来，白鼻综合征让一个又一个洞穴中的蝙蝠尽数死亡。而整窝的蜜蜂死亡的原因尚不清楚。

大部分情况下，当许多动物同时死亡时，它们会在离我们日常生活较远的地方，例如田野、山洞、森林或者国家野生动物保护区中，在这些地方动物们生活的密度过高，疾病会快速传播。

另一方面，在毕比，上千画眉在人类住宅附近的树上过夜。在新年夜的一系列烟火绽放后，这些鸟们被吓出了它们的窝。由于画眉在晚上看不见东西，它们最终到处乱飞，大部分都向下坠落。

有一只鸟还闯入了民宅，当时屋主人打开了门，想看看外面的骚动是怎么回事。大多数鸟都落在了屋顶和地上，在它们冲向死亡的瞬间发出沉闷的巨响。尸检表明有内出血，但没有杀虫剂的迹象。

“它们并非是死了以后落下的尸体，”Meese 说。“它们并非从天上落下来的。它们是从天上飞下来的。这就没那么奇怪了。”

威斯康星州麦迪逊的美国地质勘查局国家野生动物健康中心的发言人 Paul Slota 说，毕比事件的另一个独特方面在于它与噪音也有关。虽然瑞典在烟火表演之后也有鸟类死亡，他说，大规模死亡事件更多地和疾病或天气联系在一起。

“我认为实际上野生动物面对疾病时非常脆弱，常常在野生动物中发生大疫情，只是因为这些都发生在人迹罕至的地方，所以人们才常常在此类现象发生时感到非常惊讶，”Slota 说，他指出美国地质勘查局类似这样的调查报告每年都有。

“我认为人们应该明白野生动物界的死亡事件是很正常的。这就是真实的生命。”

Birds Falling From the Sky Not Unusual : Discovery NewsIt has been a bad week for wild animals.
Starting just before the turn of the New Year, 500 red-wing blackbirds died together in Louisiana. Some 100 jackdaws turned up dead on a street in Sweden. And in Arkansas, an estimated 100,000 fish went belly-up the day before 5,000 blackbirds slammed into roofs, mailboxes and the ground at full speed.
Such massive, dramatic and high profile events have fueled concerns that nature is coming to an end, or at least that something weird and disturbing is going on in the animal kingdom.
But, experts say, massive die-offs like these are not at all unusual.
From bats to whales to bees to frogs, wildlife health experts say, major mortality events happen every year for reasons that include bad weather, disease outbreaks and poisonings. The main reason this recent spate of events seems so strange is that, most of the time, mass deaths occur in places where nobody notices them.
"This is really not the unusual thing that people are trying to make it into," said Robert Meese, an avian ecologist at the University of California, Davis. "A lot of this stuff happens without anyone documenting it."
Dramatic die-offs are most common in animals that congregate or travel in large groups.
Migratory birds, for example, often become disoriented by fog or storms, causing them to run into towers, bridges, wind turbines and trees. On their long journeys, migratory birds may also accidentally ingest pesticides or even poisons that were left specifically for them. Weather can work against them, too, particularly if they migrate too soon in an unseasonably cold year.
Records kept by the United States Geological Survey list at least 16 die-offs of more than 1,000 blackbirds or starlings over the past 30 years, said Marisa Lubeck, a spokesperson for the USGS in Denver. But group deaths among animals have been going on for a lot longer than that.
In a review study published in 2007 in the journal Ibis, researchers looked through European and North American bird journals and other references dating back to the late 19th century. They found frequent reports of deaths of birds in the hundreds, thousands or more.
In one of the most extreme examples, an estimated 1.5 million Lapland Longspurs died during a March 1904 storm in Minnesota and Iowa.
And it's not just birds that can die en masse. Tens of thousands of salmon died in Northern California's Klamath River in 2002 when the water temperature got to high for them.
Strandings of whales, seals and turtles get occasional attention. In recent years, caves full of bats have been dying from white nose syndrome. And entire hives of bees have been going down for reasons that are still unclear.
Most of the time, when many animals die at once, they do it far from our daily lives in fields, caves, forests or national wildlife refuges, where animals often live at unusually high concentrations, and diseases can spread rapidly.
In Beebe, on the other hand, thousands of blackbirds had settled for the night in trees near people's homes. After a series of fireworks blasts went off on New Year's Eve, the birds were startled off their roosts. Because blackbirds can't see at night, they ended up flying all over the place, mostly downward.
One bird made it into a house, when the homeowner opened the door to see what was causing the racket. Most landed on roofs and the ground, making loud clunking noises as they shattered themselves to death. Necropsies revealed internal hemorrhaging, with no sign of pesticides.
"They weren't falling as dead carcasses," Meese said. "They didn't fall from the sky. They flew from the sky. That makes it less weird."
Another unique aspect of the Beebe incident was that noise played a role, said Paul Slota, a spokesperson for the USGS National Wildlife Health Center in Madison, Wisc. While the Swedish birds also died after a fireworks event, he said, mass die-offs are more likely connected to disease or weather.
"I think people are very often surprised that this kind of phenomenon happens, that wildlife are susceptible to disease and that there are large outbreaks in the wild, because they often go unseen," said Slota, who pointed out that the USGS investigates reports like these every year.
"I think people should be aware that mortality events in wildlife are normal. They are a fact of life."