Birdsong: It's More Than Just Music to Your Ears.

American Robin. Don Baccus Photograph (click image to hear song)

The early morning sky blushed pink as it was greeted with songs produced by a flirtatious ensemble of starlings on the power lines overhead. A robin's cheery carol and the intricate whistle of a wren drifted lightly through this concert. As in ages past, the dawn chorus had begun.

"Birdsong serves the two main functions of advertising a territory and attracting females," says Eliot Brenowitz, a professor of Psychology and Zoology who studies birdsong at the University of Washington. Additionally, some scientists think birds also sing for the pure pleasure of hearing their own voice.

Not all birds can sing. The passerines, or songbirds, comprise about half of the world's 9,500 avian species. They are characterized by their special muscular voice box, the syrinx, which consists of one set of vocal cords located at the top of each lung. Each set of vocal cords is controlled separately. This design permits birds to sing two different songs at the same time. Surprisingly, birds can also sing with their beaks closed or while they are eating.

A Male White-crowned Sparrow sings. Don Baccus Photograph (click image to hear song) James West, recordist.

Specific brain regions, or song control nuclei, play unique roles in both song learning and production, and their size apparently limits the number of songs that a bird can learn. Interestingly, some bird species, such as red-eyed vireos, have many different songs in their collection, or repertoire, while other species, such as white-crowned sparrows, sing only one or two song types.

"It is speculated that singing a number of different songs provides a more ambitious message than singing just one song," explains Brenowitz. However, it might be more favorable to produce only one song when it is important to get the message across to potential receivers. Further, it is thought that birds produce songs that travel farthest in the particular environment where they live.

Male Red-winged Blackbird in a cattail marsh. Don Baccus Photograph (click image to hear song)

"In some species, like red-winged blackbirds and canaries, the number of songs an individual produces increases with age," states Brenowitz. "The number of songs may therefore provide information about a male's relative age -- which may correlate with male quality -- to females seeking mates." Choosy females may then pass their mates' desirable genes to their offspring.

Why do females sing in some, but not all, species? "Some form of female song is probably much more common among bird species than we tend to think. Actually, cases in which females have no song may prove to be the exception rather than the rule," explains Brenowitz. However, it has been shown that males sing more often and their song is more elaborate than female song for most species that have been well studied. "This is thought to be the outcome of sexual selection in which males compete for access to females and the resources required for reproduction," Brenowitz continues.

Birdsong has many similarities to human speech. Nestlings learn songs just as children learn language; by listening to adults. When practicing their songs, young birds go through a "babbling" stage, just as humans do. Further, to develop normal song or language, both birds and kids must hear their own utterances as they practice. Moreover, both birdsong and human language are characterized by regional dialects.

It is these common features that make birds the best model to understand the role of the brain in learned vocal communication. Even though research is still ongoing, it appears that the general organization of brain pathways that integrate auditory input and vocal production share some similarities between birds and humans. Thus, birds can reveal how we evolved our own remarkable language capacities.

"I find birdsong to be endlessly fascinating," concludes Brenowitz. "Understanding why and how birds sing is like trying to understand a cryptic (to us) language. And is there a more beautiful sound than a wood thrush singing his melodic songs in a forest at dawn?"

Thanks to Eliot Brenowitz, PhD, for sharing his passion for birdsong so I could write such a fine story. Thanks to Gregory Gough at the US Geological Survey for the European Starling song file, to fellow "tweeter" James West for the White-crowned Sparrow song file. Other song files obtained from this website, unfortunately, I do not have recordists' names to credit individually. Last but not least, I would like to thank Don Baccus, photographer, for kind permission to use his images on this webpage.

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[15 March 2002]