Bloodthirsty finches on the Galapagos islands

This video say about itself:

In the Galápagos, when there’s no food to be found, the sharp-beaked ground finch adapts with a bloodthirsty appetite. Their target: nearby seabirds called boobies.

From Wired.com:

Absurd Creature of the Week: The Tiny Blood-Slurping Bird That Terrorizes the Galapagos

By Matt Simon

07.04.14

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.