Ireally enjoy autumn’s display of golden leaves, but as a bird lover in the UK, -组卷网

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I really enjoy autumn’s display of golden leaves, but as a bird lover in the UK, the real thrill at this time of year is the arrival of migratory birds(侯鸟) from Iceland, Siberia and Canada.

The UK is lucky—in winter, we get a wide variety of birds heading here to escape tough conditions further north. And in summer, we are visited by birds from Africa such as swallows and cuckoos(杜鹃) that make the most of our long, light days for having their young. While the long flights are undoubtedly impressive, there are some species that fly considerably further, spending much of their lives at the extreme ends of Earth.

The Arctic tern(北极燕鸥) has the world’s longest migration: a round-trip of 35,000 kilometers annually. Arctic terns break up their long journeys though, so if you are looking for, he world’s longest non-stop flyer, that record is held by the bar-tailed godwit(斑尾塍鹬).

So why do birds migrate? It makes sense to head somewhere warmer for winter, but it can be harder to explain why some African species then return to Europe for summer when food is still plentiful in their wintering grounds. It could be because there is less competition here, or because our longer, cooler days are useful. Some trips are even harder to explain. For example, the ancient murrelet(海雀) flies almost 8,000 kilometers from Canada to China , despite very similar conditions.

Although there is still much we don’t know, we do know that our changing climate is making birds lose the benefits of such long journeys. Arctic terns survive on sand eels(沙鳗) when they arrive in the Shetland Islands. In 2004, the UK saw a sudden drop in sand eels due to climate change. The islands usually host more than 20,000 pairs of Arctic terns, but didn’t see a single chick survive to adulthood that summer. I have so much admiration for the world’s furthest fliers, and I just hope they can cling on and that we can come to fully understand them.

【小题1】Why do some birds travel to the UK from Africa in summer?