Vampire Finches Feast On the Blood of Big Birds

The Galapagos Islands is well known to be the home for many strange and unusual animals, and one of which are vampire finches (Geospiza difficilis septentrionalis). They surely live true to their name just like the famous Dracula who sucks blood in order to survive.

A segment in BBC's Perfect Planet hosted by David Attenborough introduced the vampire finches that feast on the blood of larger birds using their sharp beak. They are mostly found in the Darwin and Wolf Islands and has some striking behavioral differences compared to other species of sharp-beaked ground finches, according to Galapagos Islands.com.

Usually, the sharp-beaked ground finch feeds on seeds and insects, but these things are not always available at Darwin and Wolf. In order to survive, they evolved into blood-sucking birds. It is believed that they have evolved this behavior from picking parasites from the feathers of Nazca or blue-footed boobies.

The Evolution of Blood-Sucking Behavior of Vampire Finches

Around 500,000 years ago, vampire finches arrived at Darwin and Wolf Islands, the two northernmost regions of the Galapagos Islands, and began to co-exist with large seabirds and had a mutualistic relationship as the finches eat the parasites in the feathers of the birds, Phys.org reported.

Later, they developed the ability to suck out the boobies' blood as well as an alternative to seeds and insects that disappear during the dry season. They learned to pierce the skin at the base of the young feathers to access the blood directly without needing the parasites anymore. Thus, having an alternating source of food and earned the nickname vampire finches.

Researchers estimated that about 10% of the vampire finches' diet is of booby blood. More so, natural selection appears to have fine-tuned their beaks for skin-piercing and blood-sucking as researchers observed significant changes in the birds' long and pointy beaks compared to non-blood-feeding finches on other islands of the Galapagos.

Furthermore, the researchers also observed very different microbiome inside the guts of vampire finches that is not similar to any other species in Darwin's species, most likely caused by consuming blood as part of their diet.

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Seeing the Vampire Finches Up Close

Researchers Daniel Baldassarre from State University of New York Oswego and Jaime Chaves from San Francisco State University visited Darwin and Wolf Islands to study the vampire finches that are very rarely visited. The birds were very isolated which means that they are abundant in the area.

They observed that many vampire finches were clamoring all over the backs, tails, and wings of the boobies as the larger birds were reluctant to abandon their nests and chicks. The finches seem to act like a true parasite that inflicts enough damage to the boobies to secure a meal without excessively harming their host.

The parasitic interaction between the two birds looks like a mosquito biting humans. Although they can tolerate the bite from the finches, the boobies consider them as a nuisance and try to get rid of them. But when it gets too much, the boobies would then fly away.

But who can blame them? The vampire finches were not just merely tapping a few drops of blood as evident to their bloodied beaks.