英语听力：自然百科 神秘的塘鹅死亡事件

 

 　　Wild life experts are trying to figure out why sick, disoriented and bruised California brownpelicans are being found in record numbers up and down the west coast of North America.

　　The birds, some of them dead, have been spotted from Washington State, to Baja California in Mexico.

　　"People are finding them in unusual places, and they are finding these birds are landing in the middle of the roads--some of them are getting hit by cars. There have been reports of birds landing in people’s backyards, which is very unusual behavior for these birds."

　　The pelican started appearing late last month in Southern California. The International Bird Rescue Research Center has received dozens of birds at two Californian facilities.

　　"They are coming in very thin and bit disoriented, usually hypothermic. "

　　They also have bruise inside their pouches and many of the birds' feet have beenswollen. Typically, this time of the year there is a significant die-off of young brown pelicans. But marine biologists say they are seeing a larger-than-normal die-off of adults, and some researchers suspect the corporate is a naturally occuring toxin found in algae.

　　"In this particular area over the last three to four years, we’ve seen a regular occurrence, typically in the spring, of a particular group of alga that's capable of producing a very powerful neurotoxin called 'domoic acid'. Through the consumption of those algae, it gets into food chains, into small fishes such as anchovies and sardines and any organism alike. A pelican eating that material can acquire enough of it that it actually causes neurological distress or even death. "

　　While disorientation is a common symptom among birds poisoned by domoic acid, the pelican’s other symptoms don’t fit their profile. So far, there are no concrete answers. Meanwhile, volunteers are nursing the feather patients.

　　"We are providing them with IV fluids, oral fluids, food, medication if necessary, and getting them eating on their own. "

　　The California brown pelican is a sub-species of the brown pelican. Over-hunting and DDT poisoning caused brown pelican populations to plummet during the first half of the 20th century. And by the early 1970s the birds were all but gone. After DDT was banned in the US in 1972, the species made a dramatic comeback.