Answer:
The size and shapes of their beaks.
Explanation:
They have different food sources, so different shaped beaks are necessary, as well as size.
Answer:
Darwin wondered about the changes in shape of bird beaks from island to island. So-called cactus finches boast longer, more pointed beaks than their relatives the ground finches. Beaks of warbler finches are thinner and more pointed than both. These adaptations make them more fit to survive on available food.
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