Brainpicker

The Brainpicker is mentioned in How to Steal a Dragon's Sword, when Fishlegs asked Hiccup what he knew about them

"they feed on people's brains by sucking them out through their ears... Although they're quite small, Brainpickers are one of the most feared dragons in the Archipelago. Even Seadragonus Giganticus Maximus are afraid of them, because nobody ''likes the idea of having their brain sucked out." -''Hiccup