The Bird With the Blood-Thirsty Beak

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The Galápagos Islands are renowned for their unique ecology and rich biodiversity. Isolated and remote, these islands are home to some of the most unique and rare species on Earth. However, hidden among the islands’ ancient tortoises and aquatic iguanas, a more sinister animal roams with a taste for blood. As you’ll see in the above video, the vampire ground finch is one blood-thirsty little bird.

The Vampires of the Galápagos

The vampire finch (Geospiza septentrionalis) is an unusual bird that only lives on two remote islands in the Galápagos: Wolf Island and Darwin Island. These two islands are about 100 miles away from any others, isolated and surrounded by nothing but water. 

Wolf and Darwin islands are small — less than a square mile each — and lack any beaches. Cliffs and sharp lava rocks surround the islands, making them very difficult to inhabit or even explore. These harsh conditions make food scarce, especially during the dry season. However, the biggest challenge for animals living on the islands is finding fresh water.  

When Natural Selection Gets Bloody

The vampire finches of the Galápagos weren’t always the blood-sucking creatures we see today. Just half a million years ago, these birds arrived on Wolf and Darwin islands and entered into a unique relationship with their booby bird neighbors.

At first, it was a win-win situation. The finches picked parasites off the booby birds and got to eat the tasty insects in return. However, as the finches became more skilled at their job, they occasionally accidentally nicked the booby birds’ skin, causing it to bleed. 

This introduced the finches to booby blood, and while they didn’t necessarily prefer its taste, it did offer something the finches desperately needed: water. It’s extremely hard to find fresh water on these isolated islands, but booby blood is packed with hydration. 

Over time, natural selection favored finches with sharper, longer beaks. These birds were better equipped to quickly and easily pierce the skin of their booby bird neighbors. Vampire finches still eat many other things, including seeds, guano, and leftovers from other predators, but they rely on blood to stay hydrated, especially during the dry season. 

Not only did vampire finches develop longer and sharper beaks compared to other Galápagos finches, but their gut bacteria also changed. Vampire finches have a very unique and specialized microbiome that helps them to better digest blood.

Are Vampire Finches Dangerous?

Vampire finches are small birds and don’t cause much harm to adult booby birds, but they certainly can be annoying. Much like our relationship with mosquitoes, vampire finches often go unnoticed, although they can become very irritating if they’re too persistent. However, they can do a lot of damage to young chicks and unhatched booby eggs, which are a rich source of nutrients.