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Question 40·Easy·Central Ideas and Details

The following text is from a magazine article about migratory birds.

Each autumn, thousands of shorebirds leave their northern breeding grounds and head south along routes that span entire continents. Although the journey is arduous, the birds have evolved a simple strategy that greatly increases their odds of survival: they time their flights so that they arrive at coastal wetlands precisely when these habitats are richest in food. In these temporary havens, the birds gorge on tiny crustaceans and worms, doubling their body weight in just a few days. The extra fat serves as fuel, allowing the travelers to cross vast stretches of open ocean without stopping. For the birds, a wetland is more than a resting place—it is a refueling station essential to the success of their long-distance voyage.

According to the passage, why are coastal wetlands important to migratory shorebirds?