Territorial male Peruvian Sheartails sing a squeaky, incessant, undirected song from territorial perches. The song has at least 4 syllables, and song bouts last variable amounts of time, up to a minute or more. This same song is produced both during courtship displays for a female (see Sexual Behavior), and syllables from the song are also uttered during agonistic interactions with other males (Clark et al. 2013).
A bird (presumably male) in immature plumage was observed singing a somewhat malformed version of the song. This observation may be of a bird in the crystallization stage of song learning.
Moreover, both sexes utter a short chip call spontaneously, both in the presence and absence of other hummingbirds, and which has an unknown function.
Like all hummingbirds, Peruvian Sheartail has a wingbeat frequency high enough that humans perceive the pressure fluctuations of the wings as humming sound. This humming sound is accentuated during courtship displays, in which the males flap their wings at a higher wingbeat frequency.
Additionally, male Peruvian Sheartails produce sounds with their tail-feathers during flight, and particularly during displays. Clark et al (2013) term these sounds "dive-sounds", as the sound appears to be homologous with similar sounds produced by related species, although in the Peruvian Sheartail this sound is not produced only during dives (see behavior, below). Baron (1897) compared the tail generated sound to the sound of "a ribbon in a strong wind". The dive-sound is a somewhat faint tonal whining sound that is composed of two to three distinct frequencies (between 0.5 and 1.5 kHz) as well as integer harmonics of these sounds. Wind tunnel experiments indicate that it is not the elongated R2 that generates the sound; it is the outer tail feathers that do. R3, R4 and/or R5 all produced distinct tones (each at a different frequency) similar to the frequencies of the dive sound, when the tips of these feathers flutter (Clark et al. 2013). Airflow over the feathers needs to exceed approximately 9 m s-1 to produce these sounds. Since hummingbirds routinely fly above 10 m s-1 during ordinary flight (Clark and Dudley 2010), this sound also occasionally is produced during ordinary flight when the birds have the tail spread, such as during maneuvers or chases.