题目内容：

    Birds in eastern North America are picking up the pace along their yearly migratory (迁移的) paths. The reason, according to researchers, is rising temperatures due to climate change.

Using migration information collected in eBird, a citizen science program database containing 10 years’ worth of observations from amateur birdwatchers, assistant professor of biology Allen Hurlbert, Ph.D., and his team analyzed when 18 different species of birds arrived at various points across their migration journeys.

Pushing migration earlier in the year could negatively affect birds over the long term, Hurlbert said. “Timing of bird migration is something critical for the overall health of bird species,” he said. “They have to time it right so they can balance arriving on breeding (繁殖) grounds after there’s no longer a risk of severe winter conditions. If they get it wrong, they may die or may not produce as many young.”

Hurlbert said, the speed at which a species migrates is the biggest influence on how strongly it responds to increasing temperatures. Slow migrators were the most adaptable to changes. Additionally, the length of the migration path affects how quickly birds move from one location to another.

“It makes sense that if you take your time to move north, you’re sort of checking out the surroundings around you,” he said. “If the conditions seem too cold, you can decide there’s no point in moving on that day. Species that tended to advance quickly, as well as those migrating from greater distances, such as Central or South America, were less able to adapt to temperature changes.”

However, being a slow traveler does not free a species from all climate change-induced migration challenges. Because they stay in one spot longer, such birds have heavier habitat and food requirements, making them more dependent upon the resources that are available along their paths. That reliance could become a greater problem if climate projections for the next 50 years to 75 years hold true, Hurlbert said. Climatologists predict the Northeast will continue to warm at a faster pace than the Southeast, potentially forcing slow migrators to move even slower and put greater difficulty on their migratory routes.

1.The rising temperatures led to _______________.

A.the speed-up of birds’ migration

B.the weakness of the birds’ physical health

C.the birds’ less demand for food

D.the variation of breeding grounds

2.According to Hurbert, wrong timing of bird migration can lead to ___________.

A.a risk of wrong migration paths B.change in life habit

C.a lack of natural resources D.decrease in bird population

3.What is the most important factor in adapting to climate change for birds?

A.The cycle of migration.

B.Migration speed.

C.Their local habitat.

D.The temperature along the migratory path.

4.What does the last paragraph mainly talk about?

A.Climatologists’ prediction.

B.Climate changes’ bad effects.

C.Challenges of slow migrators’ migration.

D.Changes of birds’ migratory routes.