The Galapagos Islands are as beautiful as they are unforgiving. Patrick Watkins could have told you as much when his captain rudely marooned him there in 1805 for acting like an ass. According to legend, mostly coming from Watkins himself, he managed to scrape by alone on the island, trading vegetables with passing ships for grog. He’d then tie on a good drunk, and the crews that intermittently landed would find him sunburned and ragged and raving, a menace no captain in his right mind would volunteer to rescue.

Watkins, though, wasn’t the only terror on the Galapagos. You see, Wolf Island, an often brutally dry rock in the archipelago, is ruled by vampires—hordes and hordes of tiny vampires. These are the so-called vampire finches, enterprising critters in a brutal environment that have figured out how to nip at the tail feathers of other birds until they draw blood, somehow without their victim putting up much of a fight. Even though they don’t sparkle or battle werewolves or whatever, they’re marvels among the many marvels that are the famed Darwin’s finches.

Ken Petren, an evolutionary ecologist at the University of Cincinnati, landed on Wolf Island in April to study these remarkable vampires, actually a subspecies of the sharp-beaked ground finch, and didn’t even lose his mind and eventually throw his colleagues overboard. “I could say that I was pretty skeptical of the whole vampire finch thing, having heard about it and realizing that there’s not a ton of data on it, mostly just some observations,” he said.

But what he found was far more macabre than the typical recorded accounts of vampire finches pestering the living daylights out of adult boobies. “On this island they really seem to be purposefully going up to a booby chick in the nest,” Petren said, “and they peck at the base of their tail where they have oil glands, and they make it bleed and they drink the blood.”

Even more menacing, they have a habit of gathering in mobs for such endeavors, watching each other intently to learn how to be unimaginably annoying for the rest of their lives. And although Petren saw them swarming dead chicks, he hesitates to conclude that the finches were responsible for the deaths. Life in this hot, dry environment is tough, so mortality rates for seabirds are quite high as it is, and he has no direct observations of finches actively hunting the babies.

Now, these young are defenseless, but why would an adult booby not just swing around and snatch up the tiny vampire? The booby’s got plenty of blood to spare, sure, but you’d imagine it’d rather hang on to it, plus there’s obvious discomfort involved.

It could be that the vampire finches are the veritable Borgs of the Galapagos: resisting them is futile. They swarm in astounding numbers—by Petren’s reckoning, they outnumber every other finch species on all of the islands combined—so it may be that putting up a fight is simply worthless. Fight off one vampire and others will just take its place like miniature hydras.

It might also be an extension of cleaning behavior. Indeed, “we saw on this trip the finches on some of the iguanas picking off ticks,” said Petren. It may well be that the vampire finches once provided the service to seabirds, before realizing there’s a better payday in digging deeper for blood, which is quite energy-rich (just ask vampire bats or mosquitoes or Mike Tyson).

Even living in a nice shell won’t save you from the vampire finches. They’re on the lookout for eggs to steal, too. “The birds will put their head down on the ground and lift their feet up and push eggs so the eggs will roll off a cliff and break,” said Petren. “And then they go hovering in and sip up all the yolk.”

“And it’s funny,” he added. “As you get one that’s sitting there trying to roll an egg, all of the other ones come around and they’re watching, and they’re watching, and they’re waiting in this little crowd of vampires all waiting for the goods to be spilled. And each one will take his turn and go in there and try to roll the egg.”

Blood and eggs are just two of the many items on the vampire finch’s menu, though. It’s a generalist, also taking seeds and even drinking up the vomit of other birds, because why the hell not. The vampire’s wickedly sharp beak is perfectly adapted for this lifestyle, allowing it to not only pierce flesh but to also open up fruits and drink nectar. It has to be creative on this unforgiving island, especially during droughts, when finch populations can crash by as much as 90 percent, according to Petren.

The other finches on the islands vary greatly in the size and shapes of their own beaks, each suited to a specialty, like bigger beaks for crushing tough seeds. These birds are collectively known as Darwin’s finches, and they’re a lovely manifestation of how evolutionary time brings about adaptations to an environment. Evolve a bigger beak, say, and you can eat seeds other birds can’t, boosting your chances of survival (and earning you a fair amount of dirty looks from other species).

But countless years of beautiful evolution can’t prepare finches and other critters for the only force on these islands more deadly than drought: human beings. We’ve introduced countless invasive species to the Galapagos Islands, from goats to ducks to wasps, and while most native species haven’t yet faced collapse, authorities are constantly battling to keep the invaders in check. But luckily, Wolf Island, home of the vampire finch, is one of a few remaining archipelagos that’s pristine, only because scientists like Petren go through rigorous quarantine before they’re allowed to land (tourists are forbidden from stepping foot here, but are allowed to dive around the island).

In many habitats in the Galapagos, including on Wolf, species have evolved without fear of predators, making them that much more vulnerable to invasive species. But that tameness is also a boon to human observers. “The behavior of the animals is just incredible,” Petren said. “They just ignore you, and very few places on Earth are like that. So you will see everything up close and personal, and that’s what really makes it special.”

They apparently aren’t even embarrassed by us watching them eat puke. Own it, little vampire. Own it.

Browse the full Absurd Creature of the Week archive here. Have an animal you want me to write about? Email matthew_simon@wired.com or ping me on Twitter at @mrMattSimon.