The nutrition of all of Darwin's finches is different. What they eat is determined by the shape and size of their beaks. Their diets vary by eating seeds, fruit, invertebrates, and drinking from cactuses.

The sharp-beaked ground finches mostly feed on seeds and invertebrates. Their sharp beaks also enable them to drink for the cactuses. But what makes them unique to all of the other finches, is that they will drink the seabirds blood in times of drought. They will peck on the boobies until blood is drawn and will drink it to provide the nutrition they need.
They will also crack open the Boobies eggs and eat the inside. They will roll the egg into a rock with their feet until the egg cracks and they are able to eat it.

Other organisms who drink blood are spectral bats, leeches, and fleas.
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