Vampire Ground-Finches menace their victims in broad daylight, stabbing holes in their flesh, then devouring the blood. During the dry season, when their usual diet of seeds can be scarce, they turn to large seabirds, like boobies. Fluttering onto a booby’s back, the finch jabs its sharp beak in among the feathers until blood flows, making a meal of it. Why boobies tolerate this remains a mystery.

More info and transcript at BirdNote.org. 

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