The blood-drinking vampire finch
Maja Mielke
Vampire finches from the Galápagos Islands drink the blood of other birds to survive the dry season.
The white feathers of the Nazca booby are soaked with blood as the little brown finch keeps pushing its beak into the open wound. More finches arrive, taking turns to drink blood from the booby, their beaks stained red. It is the dry season on the Galápagos Islands. Food and water are scarce—it’s a time of sheer survival. These finches, however, have found an unusual way to avoid starving to death: they drink the blood of other birds. They’re vampire finches.
A vampire finch. Illustration by Maja Mielke.
The vampire ground finch (Geospiza septentrionalis) is native to Wolf and Darwin Island, two tiny islands in the north of the Galápagos archipelago. It is one of 19 species of Darwin’s finches, but the only one that relies on blood as a food source when other resources become scarce. They drink the blood of Nazca boobies and blue-footed boobies, large seabirds that are regular visitors to Wolf and Darwin Island.
To get their blood meal, vampire finches hop on the back of a booby and peck at its skin until blood is drawn—a behavior that probably evolved from the finches pecking parasites off the boobies’ plumage. The most fascinating aspect of this seemingly violent behavior is that the boobies don’t seem to object—they behave as if nothing special is happening. Nobody knows why that is.
In 2018, a team of researchers reported1 that vampire finches host a special gut microbiome because of their unusual diet. In contrast to other Darwin’s finches, their guts contain bacteria that are commonly present in vultures and alligators (!). Wild.
Now, you can watch the vampire finches in action. If you can stand the sight of blood, take a look at this video, narrated by David Attenborough for A Perfect Planet: Link to video
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