For mammals, the outer ears of mammals play an important function in helping identify sounds coming from different elevations.
Since birds have no external ears, how do they accomplish the same thing? They utilize their entire head, according to a new paper in PLOS ONE
"Because birds have no external ears, it has long been believed that they are unable to differentiate between sounds coming from different elevations," explains Hans A. Schnyder, Technische Universitaet Muenchen
Chair of Zoology. "But a female blackbird should be able to locate her chosen mate even if the source of the serenade is above her."