Perched on a flowering shrub on a windy Andean mountainside, the tiny Ecuadorian Hillstar hummingbird chirps songs of seduction that only another bird of its kind can hear. For the first time, scientists have shown that these hummingbirds can sing and hear in pitches beyond the known range of other birds, according to research published Friday in the journal Science Advances. The male’s ballad is sung at around 13.4 kilohertz.