Males (and apparently not females) are highly vocal, singing from exposed perches on their territories. Males turn their head from side to side as they sing. The song is produced over most of the day, probably for the entire duration of the breeding season, which is prolonged (see breeding, below). The song is complex, consisting of several syllables (see figures 1, 2; also, XC 30511) which are sung in rapid succession within a song bout. Individual males may repeat the same syllable within a given song bout. Extensive recordings of a single male indicate song bouts are somewhat indeterminate in length, lasting 12.0 ± 6.4 (n ± s.d.) seconds (Clark 2006). Within a song bout, the syllables do not appear to be entirely random in order, but it is not possible to determine if there is a set song syntax without additional sound recordings. Clark (2006) indicates that, while on his territory, one male spent 33% of the time actually engaged in singing. Comparison of recordings from 2005 (figure 1; CJC) and 1992 (figure 2; British Library recording #34377), both from Jamaica, suggest few shared syllables, indicating strong geographic, year-to-year, or individual variation in song structure.
In addition to perched song, males will sing on the wing when approaching or departing their territory, and also sing during aerial displays to other birds (see below). The function of song appears to be related to territoriality, potentially to announce territory ownership to other males and/or females, and thus it is likely to be sexually selected. It is unknown if the song is innate or learned. It is possible there are undocumented, subtle daily patterns of song production, but generally, males sing over the entire day.
Of note, recordings of songs of the Vervain Hummingbird in the Macaulay Library from the Dominican Republic (#35315, #35319) and Jamaica (#35356) sound subtly different (perhaps more nasal and squeaky) from those for M. minima minima presented in the figures below. It is not clear whether this variation could be due to cultural evolution, individual differences, sub-specific variation, geographic variation, or different recording conditions or equipment.
A dry “chittering” scolding sound is produced by both sexes during agonistic interactions (see below). This scolding call is higher-pitched but otherwise similar (both in social context and in acoustic form) to the scolding call produced by the Anna’s Hummingbird (Calypte anna Lesson). Below is a spectrogram of this sound, generated by a female.