Thousands of birds die each spring and fall when they collide with Chicago’s skyscrapers, which lie on a major migration path between Canada and Latin America. But the birds don’t die in vain. Since the 1970s, many of them have been collected from the street by the city’s Field Museum. They were classified and recorded in detail there. This unique and detailed set of data has been a scientific windfall(意外之财), revealing that North American migratory birds appear to be shrinking.

A new study of this data has highlighted an important trend: Birds that have bigger brains, relative to their body size, are not shrinking as much as the smaller-brained members of their species. The study is the first to identify a potential link between cognition and animal response to human-made climate change, according to the researchers from Washington University in St. Louis. “As temperatures warm, body sizes are decreasing,” said Justin Baldwin. “But larger-brained species are declining less strongly than small-brained species.”  

Relative brain size is often considered an indicator(指标) of behavioral flexibility in birds, according to the research. The idea is controversial when it’s applied to some other animals, Baldwin said, but it works for birds. “Relative brain size connects with increased learning ability, increased memory, longer lifespans and others,” Baldwin said. “In this case, a bigger-brained species of bird might be able to reduce its exposure to warming temperatures by seeking out habitats with cooler temperatures, for example,” he said.

Birds that had big brains, relative to their bodies, had body-size reductions that were only about one-third of those observed for birds with smaller brains, the study found.

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1.Why did some birds die on the way of migration?

A Barriers were set up on the migration path.

B The weather became extremely cold.

C They crashed into the tall buildings.

D The spring and fall changed quickly.

解析：选C。C 细节理解题。根据第一段第一句的“when they collide with Chicago’s skyscrapers”可知这些鸟在迁徙途中会撞上芝加哥的一些摩天大楼。故选C。

2.What happened to the dead birds?

A They were kept and studied later on.

B They were buried in the same streets.

C They were taken away from the path.

D They were used to show migratory way.

解析：选A。A 推理判断题。根据第一段最后两句的“Since the 1970s, many of them have been collected from the street by the city’s Field Museum. They were classified and recorded in detail there.”可知这些死鸟的尸体被保存起来进行了分类研究。故选A。

3.What did the smaller-brained birds do to adapt to the climate change?

A They tried to get smaller weight.

B They reduced their body size.

C They chose the familiar streets.

D They lost all their members.

解析：选B。B 推理判断题。根据第二段的“As temperatures warm, body sizes are decreasing,” said Justin Baldwin. “But larger-brained species are declining less strongly than small-brained species.” 可知这些大脑较小的鸟通过缩小体型来适应气候变暖。故选B。

4.How will bigger-brained birds protect themselves from the warming temperatures?

A By increasing their memory.

B By having longer lifespans.

C By finding cooler homes.

D By changing their behavioral flexibility.

解析：选C。C 细节理解题。根据第三段的“a bigger-brained species of bird might be able to reduce its exposure to warming temperatures by seeking out habitats with cooler temperatures”可知，头脑较大的鸟类可能会通过寻找温度较低的栖息地来减少它们暴露在变暖的温度下。故选C。