Songbirds: Nature’s Carolers

It’s 7 a.m.: The dawn chorus begins.

On the Embry-Riddle campus and in surrounding neighborhoods, a notable vocalist in the choir is likely to be quail, the roughly football sized bird with a large plume hovering above their black faces. These ground dwellers with gray necks, wings and back can be seen poking out of the low-growing native brush, or perhaps scuttling across the roads. Watch out!

The quail’s chirps and coos, short sweeps from low to high notes and occasional faster sequences carry their specific meanings to convey. The distinctive three to four note call means a quail has been separated from its flock, while the quick chirp-chirp-chirp comes after a suspicious threat is identified.

We call this language “bird song,” but is it really music?

Songbirds, the term referring to a specific suborder of birds, includes about 4,000 species. Though the species considered songbirds vary in size, coloring, features, geographical locations and more, they all have one thing in common: the vocal organ called the syrinx.

Non-songbirds make simple, instinctual sounds, whereas songbirds learn to use their syrinx as an instrument, with their parents and community acting as their vocal coaches.

The syrinx, located below the windpipe, is a complex structure of cartilage and membrane, which, when vibrated, produces an extensive range of sound. Some songbirds are capable of controlling the left and right halves of their syrinx separately, effectively singing with two voices at once.

Each species carries its own unique tunes and species themselves often fragment into regional dialects. As a baby songbird learns its songs from its parents, the birds carry generational knowledge that differs from a bird’s just one mountain pass away.

Songs and calls carry different meanings, from threat detection to the selection of mates. Some species, mostly tropical birds, sing a complex duet as part of a bonding ritual in the mating process. The plain-tailed wrens, found in the Andes of southern Colombia, Ecuador and northern Peru, create an impressive song together by carefully alternating notes in a shared melody.

Researchers at Johns Hopkins University identified in the study “Neural Mechanisms for the Coordination of Duet Singing in Wrens” that each bird constructs the entire melody in their heads individually and identifies appropriate sections to leave for their partner. What emerges is one song, sung by two. They even adjust their timing and pitch to maintain the song together.

While the wrens’ unique ability is in their co-operative skills, another bird stands out in their note selection. A 2014 study “Overtone-Based Pitch Selection in Hermit Thrush Song” identified a convergence with the notes used by the hermit thrush with scales commonly used in human music.

The researchers identified that songs from the hermit thrush favor frequency ratios derived from the harmonic, also called overtone, series. A harmonic series is one in which each frequency is an integer multiple of a fundamental tone.

A harmonic series can be created from a single string, held firmly at both ends. The fundamental note is created simply by plucking the entire string. Anchoring the string in the middle and plucking half creates the second overtone, one octave higher than the fundamental tone. Division into three creates the third overtone, and so on.

The harmonic series serves as the basis for many human musical scales, especially prevalent in Western music. Exactly why the hermit thrush prefers it is unknown, but it is not due to physical constraints as researchers displayed that the tonal selection is an active choice in the bird’s brain.

There remains much to be learned about bird songs. A debate throughout the birding and research community has been raging for decades over whether birds ever sing purely for their own enjoyment, but conclusive evidence either way has yet to be found.

For now, it is enough to simply enjoy their tunes in the early hours of the morning. Whether or not it is music to them, it registers as music to human ears, starting our days with lively melodies from those little birds outside our windows.

This piece was originally published on Jan. 26, 2022 in Horizons Newspaper, the student-run publication from the Embry-Riddle Aeronautical University's Prescott campus.