Scientists believe that vampire sparrows have developed blood-consuming behavior to survive in harsh environments and limited resources.
The Galapagos Islands are home to 13 different species of Darwin’s finches that evolved from a common ancestor. Each species of sparrow adapts to its own environment and adapts its diet. Some birds will love to eat seeds, pistils, pollen and insects, while others prefer to drink the blood of large seabirds.
On the islands of Darwin and Wolf, located in the vast marine reserve of the Galapagos Islands, there are sparrows that specialize in consuming blood. First discovered in 1964, the vampire sparrow Geospiza septentrionalis used its sharp beak to stab the wings of the large seabird Sula granti and drink its blood.
Drinking blood might seem like an unusual diet for sparrows, but given the sparrow’s adaptability, it’s not too surprising a behavior. Sparrows were most likely to arrive on Darwin and Wolf Islands 500,000 years ago. Charles Darwin, an English naturalist, arrived on the Galapagos Islands in September 1835. Darwin observed the difference in the diets of sparrows on different islands, then examined the size of their beaks. The size of the beak changes as the sparrow develops a different taste than the food available.
Since the islands are all remote, which is extremely harsh, food can become scarce during the dry season. The vampire sparrow lives with seabirds, including the red-legged booby and the bird Sula granti, which feed on the parasites that inhabit the skin and feathers of these large birds. They may develop a preference for drinking blood when they create an open sore while catching the parasite. Finally, sparrows learn to access blood by pecking the wings of the large bird. Sparrows that vampires will live by drinking blood when they cannot find other food sources such as seeds and insects, according to researchers Kiyoko Gotanda of the University of Cambridge, Daniel Baldassarre of the University of New York and Jaime Chavez from Great San Francisco School. But the blood is not an essential source of nutrients because it contains large amounts of salt and iron.
The vampire sparrow has a type of intestinal bacteria, Peptostreptococcaceae, which can help process and digest salt and iron. Even when this is not the most effective source of nutrients, in the absence of food, they easily attack seabirds and young. They deliberately peck the tail where the baby bird’s oil gland is located and drink the bleeding.