January 22, 2025, 9:30 am | Read time: 4 minutes
Did you know that there are birds that feed on blood? The animals live on the Galapagos Islands and are aptly named vampire finches. One species is particularly greedy for the lifeblood of other animals and has now been declared the “most bloodthirsty” bird in the world by the “Guinness Book of Records.”
When you think of blood-drinking animals, you probably think of mosquitoes or bats first. Many people are unaware that birds also feed on blood. This is no wonder because vampire finches are found exclusively on the Galapagos Islands. They also form a subgroup of the well-known Darwin’s finches. One particular species, the vampire ground finch (Geospiza septentrionalis), was recently named the “most bloodthirsty” bird in the world by the “Guinness Book of Records.” 1
What are Vampire Finches?
Vampire finches belong to the passerine family. They are, therefore, related to our native sparrows. And when the birds are not pecking at their victims with blood-smeared beaks, they actually look quite cute. The vampire ground finch, which has been awarded a prize by the Guinness Book of Records, is only between eleven and twelve centimeters in size. This makes it smaller than the well-known tree sparrow.
The birds are only found on the two small islands of Wolf and Darwin, which are part of the Galapagos archipelago. This is an arid environment with comparatively little varied shrub vegetation. Every year, there are distinct rainy and dry seasons, which the birds have to adapt to in order to survive, as they do not leave the area. And this is also the reason for the special diet of the vampire finches.
Why Do the Birds Drink Blood?
Actually, finches feed primarily on seeds and insects – including the vampire finches. In the wet months, when there is a lot of rainfall, the birds eat insects and small invertebrates such as worms as well as plant food. However, in the dry season, food and water supplies become scarce. The birds then have to drastically change their diet and switch completely to animal food.
This consists largely of the blood of gannets. The seabirds breed on the islands during this time. The vampire finches specifically fly to the gannets’ backs and peck at the base of the quills until a bleeding wound appears. In addition to absorbing nutrients, the blood also covers the birds’ need for fluids during the dry season on the islands.
Biologically speaking, drinking blood is a unique and highly specialized diet in vertebrates. This is because the digestion of animal blood requires very special intestinal bacteria. Studies have shown that the blood finches actually seem to have them. And that’s not all: a 2019 study showed for the first time that the gut bacteria of blood-drinking vampire finches are similar to those of vampire bats living in Central and South America.
Do Vampire Finches Harm their Host?
Although there are observations that whole flocks of vampire finches can sometimes attack the gannets’ open wounds, this is not life-threatening for the host birds. However, the wounds could become infected and contribute to the weakening of the birds.
The situation is different for gannet chicks. If they are pecked at by a vampire finch, the attack can cost them their lives. The same applies to the eggs, as the vampire ground finches do not eschew these either. 2
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Are Vampire Finches Dangerous to Humans?
Vampire finches are highly specialized birds. They know exactly how and where to peck at their host birds in order to get food. Such a host-parasite relationship usually develops over centuries or even millennia. In most cases, the parasite adapts to a specific host – in this case, the gannets. So, anyone visiting the Galapagos Islands in the near future should not have any fear of being attacked and bloodily pecked by vampire finches. Even other bird species or animals would not fly at the finches.
Unfortunately, the Guinness Book of Records does not explain why the vampire ground finch was chosen as the “most bloodthirsty” bird in the world and not another species of vampire finch. PETBOOK, therefore, asked the editors but did not receive an answer by the editorial deadline on January 8.
About the author: Dr. Saskia Schneider holds a doctorate in biology. During her studies at the Free University of Berlin, she focused on zoology and animal behavior.