揽瓜阁俱乐部第三期 Day6 2020.07.25
【自然科学-动物】 The Birdsong That Took Over North America （1051字 精读 必做篇）
The birds were singing something strange.
Ken Otter and Scott Ramsay first noticed it in the early 2000s, when they were recording white-throated sparrows in Prince George, a city in western Canada. The birds are so ubiquitous across the country, and the male's song so distinct, that bird-watchers have put words to it: Oh sweet Canada, Canada, Canada. But the white-throated sparrows in Prince George were singing something different. They had lopped a note off Canada, so the song sounded more like Oh sweet Cana, Cana, Cana.
At first, Otter and Ramsay, biologists at the University of Northern British Columbia and Wilfrid Laurier University, respectively, thought they had simply discovered a new song dialect unique to sparrows in Prince George. But an even stranger pattern emerged when they and a small team of researchers spent the next two decades gathering archival recordings, crowdsourcing bird songs, and driving hundreds of miles through Canada to record white-throated sparrows. According to a new study out today, the song they first heard in Prince George had spread east across the country—at remarkable speed. By 2017, all white-throated sparrows in western Canada were singing the new song variant and half were singing it as far east as Ontario. Oh sweet Cana, Cana, Cana is taking over Canada.
“The national pride of Canada is hinging on this,” jokes Jeff Podos, a biologist at the University of Massachusetts at Amherst, who was not involved with the study. More seriously, says Podos, seeing changes in a feature as basic as the number of notes in a song is striking. “Just to be able to see the speed of this change is really amazing,” he adds. Scientists still don't know how the song variant managed to spread so completely across an entire country.
Otter and his team think the Cana variant of the song originated in western Canada between 1960 and 2000. Archival recordings of white-throated sparrows before that all ended in the classic Canada. Once the team heard the strange new variant in Prince George, they started looking east, especially in Ontario's Algonquin Park, where scientists have long been monitoring a population of white-throated sparrows. They didn't find a male singing Oh sweet Cana in Algonquin Park until 2005. They found two more in 2007. Over the years, the number steadily increased until 44 of 92 males they recorded in 2017 were singing Oh sweet Cana. Meanwhile, in Alberta, in western Canada, surveys in 2004 and then 2014 found that the Cana variant had completely replaced Canada between the two surveys. Hundreds of additional birdsongs uploaded by birders to sites such as eBird and Xeno-canto corroborated the findings.
The new song variant had clearly spread west to east, but how? From 2014 to 2016, Otter and his team were able to recover nine sparrows that they tagged with geolocators. White-throated sparrows spend most of the year in Canada and the northeastern United States, but they migrate to warmer places during the winter. These geolocators showed that birds from both western and eastern Canada spent the winter in overlapping areas in eastern Texas, Oklahoma, Arkansas, and Kansas. “It gave us the idea that maybe what's happening is these birds are singing on the wintering grounds and becoming song tutors for birds that live east of the Rockies,” Otter told me. Birds from the West were meeting young sparrows from the East—and possibly passing on Oh sweet Cana.
Young sparrows indeed have a sensitive period when they learn to sing, says Jill Soha, a birdsong researcher at Duke University, who was not involved in the study. Once this period is over, their songs remain mostly fixed for the rest of their life. But Soha wonders whether the young sparrows, who hatch in the spring and summer, would already be too old to learn by the time they migrate to their wintering grounds. “From lab studies,” she says, “they shouldn't be learning new songs after about 100 days of age.” If young white-throated sparrows really are picking up the Cana song variant over the winter, that would challenge the conventional wisdom on how the birds learn. Otter said he thinks mixing over the winter has to play a role because Oh sweet Cana could not have spread so quickly, based on models, if it were simply diffusing from west to east.
Regardless of how the birds first encounter the new song variant, something about it must be especially desirable. In white-throated sparrows, males sing to warn off other males and attract females. (Some females also sing, but their songs are slightly different.) Otter speculated that female sparrows might prefer the new song variant in mates. This spring, his team was planning to capture female white-throated sparrows to test their reactions to the two song variants in a lab, but the pandemic upended those plans. He hopes to test the idea next year. Stewart Janes, a biologist at Southern Oregon University, who was not involved in the study, agrees that female choice could be driving the change. “But why so complete? And so quick?” he asks. “All of a sudden, there's something apparently really sexy about just a slight change that happened in the white-throated sparrow songs, and it's a hot new thing.” The preference could signal a cultural change among sparrows, not unlike the way people flock to skinny jeans or cold-shoulder tops depending on the latest fad.
Bird trends are getting easier than ever to spot. New technology, such as autonomous recording units that can be left at a field site, is helping bird researchers capture more recordings than ever before. And amateur birders—armed with a digital recorder or even just their phone—are uploading birdsongs in droves online. This citizen science, says Karan Odom, an ornithologist at Cornell University, is “really changing the kind of science we can do and the kinds of questions we can ask.”
As researchers listen to bird recordings, they may find that Oh sweet Cana is not unique in sweeping across a continent. It could be happening in other places and with other bird species. Otter said that he's already noticed that a modified version of the Cana song is growing in popularity in Prince George in recent years. It might not be long before Oh sweet Cana becomes old news too.
Source: The Atlantic
【自然科学-动物】 Licking bees and pulping trees: The reign of a wasp queen （671字 4分53秒 听力 必做篇）
先做听力再核对原文哦~
听力视频下载链接及提取码： 提取码：3g5r
As the April sun rises on a pile of firewood, something royal stirs inside. This wasp queen is one of thousands who mated in late autumn and hibernated through the winter. Now she emerges into the spring air to begin her reign.
Most of her sisters weren’t so lucky. While hibernating in compost piles and underground burrows, many sleeping queens were eaten by spiders. Warm winters caused by climate change led other queens to emerge early, only to find there was no available food. And some queens that survived the winter fell victim to the threats of spring, such as carnivorous plants, birds, and manmade pesticides. Our queen is the lone survivor of her old hive, and now, she must become the foundress of a new one.
But first, breakfast. The queen heads for a citrus grove full of honeybee hives. The bees can be dangerous if provoked, but right now they’re paralyzed by the morning cold. Their hairy bodies are dripping with sugar water from an earlier feeding, and the resourceful queen licks them for a morning snack.
Newly energized, our queen searches for a safe nesting area. This tree hollow, safe from rain, wind, and predators, is ideal. She chews the surrounding wood and plant fibers to make a paper-like pulp. Then she builds around 50 brood cells that comprise the beginning of her nest. Using sperm stored from last fall, the queen lays a fertilized egg into each cell, producing as many as 12 in 20 minutes. Within a week, these will hatch into female larva.
But until then, the queen must hunt down smaller insects to feed her brood, all while expanding the hive, laying eggs, and defending against intruders. Fortunately, our queen is well prepared. Unlike bees, wasps can sting as many times as they need to.
With such a busy schedule, the queen barely has time to feed herself. Luckily, she doesn’t have to. When she feeds an insect to her grubs, they digest the bug into a sugary substance that sustains their mother. By the end of July, these first larva have matured into adult workers, ready to take on foraging, building, and defense. The queen can now lay eggs full-time, sustaining herself on her worker’s spoils and their unfertilized eggs.
Although each worker only lives for roughly 3 weeks, the queen’s continuous egg-laying swells their ranks. In just one summer, the nest reaches the size of a basketball, supporting thousands of workers. Such a large population needs to eat, and the nearby garden provides a veritable buffet. As the swarm descends, alarmed humans try to swat them.
They even fight back with pesticides that purposefully poison wasps, and inadvertently impact a wide-range of local wildlife. But the wasps are actually vital to this ecosystem. Sitting at the top of the local invertebrate food chain, these insects keep spiders, mites, and centipedes, in check. Wasps consume crop-eating insects, making them particularly helpful for farms and gardens. They even pollinate fruits and vegetables, and help winemakers by biting into their grapes and jump-starting fermentation.
This feast continues until autumn, when the foundress changes course. She begins grooming some eggs into a new generation of queens, while also laying unfertilized eggs that will mature into reproductive males called drones. This new crop of queens and males requires more food. But with summer over, the usual sources run dry, and the foraging wasps start taking more aggressive risks.
By September, the hive’s organization deteriorates. Hungry workers no longer clean the nest and various scavengers move in. Just when it seems the hive can no longer sustain itself, the fertile queens and their drones depart in a massive swarm.
As the days grow colder, the workers starve, and our queen reaches the end of her lifespan. But above, a swarm of reproductive wasps has successfully mated. The males die off shortly after, but the newly fertilized queens are ready to find shelter for their long sleep. And this woodpile looks like the perfect place to spend the winter.
Source: TED
【笔记格式要求】
精读笔记格式要求： 1.总结文章中心大意 2.总结分论点或每段段落大意 3.摘抄印象深刻或者觉得优美的句子 4.总结文章中的生词 5.记录阅读时间、总结时间、总时间
精听笔记格式要求： 1.逐句听写整篇文章 2.对照原文修改听写稿，标记出错原因 3.总结文章中心大意 4.总结精听过程中的生词 5.记录听写时间、总结时间、总时间
泛听笔记格式要求： 1.听整篇文章，总结文章中心大意 2.对照原文，总结泛听过程中的重点生词 3.记录泛听次数、总时间
这里也给大家三点学习小建议哦~ 精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~ 精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~ 泛听：每次听全文，边听边记录，不要逐句听或中间暂停，如果听 5 遍都没听懂，那就对照原文总结大意和原因，时间宝贵，不要过于执着哦~
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发表于 2020-7-24 22:24:45
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