1 . Hotter, drier conditions over the past four decades have been decreasing the rainforest birds’ body size while lengthening their wings, a study published in the journal Science Advances said on Friday. “This maybe an adaptation to hotter temperatures. Even in the middle of the primitive Amazon rainforest, we are seeing the global effects of climate change caused by people,” said Vitek Jirinec, lead author on the study.
The scientists have studied measurements and weigh-ins of 77 different bird species in the Amazon rainforest since the early 1980s. Nearly all of the bird species have gotten lighter as time goes on. On average, most species became about 2% lighter every decade. These birds don’t vary that much in size,” said co-author Philip Stouffer, a professor of conservation biology at Louisiana State University. “But when everyone in the population is a couple of grams smaller, it’s significant.”
The researchers found that bird species living in higher parts of the forest—as opposed to closer to the forest floor —saw the most pronounced changes in terms of body composition. Those are the species most exposed to high temperatures. Longer wings and smaller bodies mean that birds have to useless energy to move around, helping them stay cool.
Brian Weeks of the University of Michigan in 2019 researched the average sizes of 52 species of migratory birds in North America from 1978 to 2016. He also found all of them had smaller bodies and longer wings in 2016. This is another example of climate change-human actions globally—affecting a fundamental thing such as the size and shape of the birds. The same effect is likely to be true of other species across the world living in extreme environments.
1. What does the new study find about the birds in the Amazon rainforest?
| A．They are flying much higher. | B．They have been physically longer. |
| C．They are more flexible than adaptable | D．They have got smaller and longer-winged. |
2. How did researchers conduct their study?
| A．By analyzing the collected data. | B．By referring to historical records. |
| C．By observing birds in the forests. | D．By cooperating with other research groups. |
3. What made the birds living in higher parts of the forest change most?
| A．Less food available. | B．Decreased forest area. |
| C．Most exposure to the heat. | D．Inadequate shelter from storms. |
4. What is the function of the last paragraph?
| A．To introduce a new topic. |
| B．To further stress bad effects of humans. |
| C．To popularize some knowledge about birds. |
| D．To tell the difference between the two studies. |
