Two words that are usually said together: bird song, or better yet songbirds, those usually small birds in your garden that produce the wonderful, lilting, sometimes piercing, often warbling, unique collection of notes that identifies each species.
But not all songbirds sing, or sing exclusively — some of them have adopted a buzz as part or all of their song. In fact, their soft buzzes or wheezes are remarkably similar and difficult to pinpoint when looking for that buzzing bird that you’re not really sure isn’t some sort of insect. Why would male birds want to buzz instead of sing?
Take the Blue-winged Warbler for example; wouldn’t you assume from its name that its song would be a melodious warble, rather than a two-note “bee-buzz“?
Just 20 feet away, a Clay-colored Sparrow is buzzing away, with a very similar, low frequency, raspy buzz call.
Buzzing seems to be a common characteristic of “song” in grassland birds, like Grasshopper Sparrows and Savannah Sparrows. So, one wonders if these birds are trying to avoid detection in prairie habitat by mimicking insects when they “sing”, or whether female birds just find buzzing particularly enticing?
It turns out that buzzing sound made with the bird equivalent of a larynx (called a syrinx), is actually quite physically challenging, and therefore could be an indicator to females of the quality of a potential mate. German researchers* found that larger, more robust male Nightingales incorporated more buzzes in their song, and enjoyed greater attention from females than their less robust or younger competitors.
Another possible explanation for buzzing birds found in grassland habitats is that low frequency buzzing notes apparently carry long distances, and can be heard throughout and beyond the male’s territory. Banded Wrens incorporated more buzzing notes in their early morning song that was directed toward other males in the nearby vicinity, at times before females were present.**
*Citation: Weiss M, Kiefer S, Kipper S (2012) Buzzwords in Females’ Ears? The Use of Buzz Songs in the Communication of Nightingales (Luscinia megarhynchos). PLoS ONE 7(9): e45057. https://doi.org/10.1371/journal.pone.0045057
**Citation: P.L. Trillo and S.L. Vehrenkamp. Anim Behav. Song types and their structural features are associated with specific contexts in the Banded Wren. 2005 Oct; 70(4): 921–935. https://dx.doi.org/10.1016/j.anbehav.2005.02.004