The Black-breasted Puffleg ( Eriocnemis nigrivestis ) is a species of hummingbird endemic to Ecuador . The average length of the black-breasted Puffleg is 8.5 cm . The Black-breasted Puffleg ( Eriocnemis nigrivestis ) is an average sized ( 8.5 cm in length ) species of hummingbird endemic to Ecuador .