The black-thighed puffleg (Eriocnemis derbyi) – also known as Derby's Pufflegs – has black feathering around its legs which is unique among the pufflegs. The pufflegs are small to medium-sized South American hummingbirds that were named for their distinctive dense feathering around their legs known as "leg puffs" - which are unique among the pufflegs. It is found at humid forest edge and ravines in the Andean highlands of Colombia and northern Ecuador. It is threatened by habitat loss.