Wednesday, September 4, 2013

Who Said What? (A Guest Post)

By Porscha Carriveau


As an aviculturist-turned-scientist, to me, it is common sense to tell people that birds are heard more often than seen. People study bird songs or calls for a variety of reasons. The reason I study bird songs is to identify the songs that my African grey parrot has learned to mimic. His repertoire includes the vocalizations of several birds’ songs such as robins, cardinals, cat birds, and chickadees. He also mimics humans. When leaving home in the morning, the last thing that I hear heading out the door is "gotta go to work" and the sound of being blown a kiss. Most people would think nothing of it, but I am being told this by a bird that has no lips.

Here is an example of an African grey parrot producing sound :



Humans produce sound by using their vocal tract, which includes the larynx (known as the voice box), where the vocal folds are located. Sound is produced with the help of the trachea, which controls air flow through the larynx. In the larynx the vocal folds make sound by vibrating. The remainder of the vocal tract includes the throat, nose, tongue and lips which are involved in the articulation of speech. On the other hand, parrots have a syrinx (what rivals the larynx), a trachea, a tongue and a beak. This means that birds do not have vocal cords to produce the sounds that we as humans make; they instead have two air passages that come together at the organ known as the syrinx creating a vibration that produces sound.


A Quaker parrot shows off his beak
and tongue. Photo by Alex Nelson
at Wikimedia Commons.
From my experiences working with and owning a variety of parrots, I would say that African grey parrots and monk parakeets (also known as Quaker parrots) are the two clearest and best mimicking parrots. Quaker parrots originate from South America. Over the years these birds have learned to adapt to their environment extremely well, leading to the birds becoming an invasive species in many parts of the world, including several U.S. states where they are now illegal to own as pets.

Research done by Verena Ohms, GabriĆ«l Beckers, Carel ten Cate and Roderick Suthers recently set up a study using x-ray imaging to determine what is taking place in the vocal tract of a Quaker parrot while producing species specific calls. To do this, a piece of metal wire was placed on the underside of a Quaker parrot’s tongue and two pieces of wire were placed inside the trachea attached to tracheal rings. Here is an example of what researchers were looking at which allowed them to monitor the bird’s tongue, beak, and trachea movements.

Researchers looked specifically at a few measures when a bird produces sound: the bird’s tongue height (TH), the size of the beak opening (BO), and the amount of tracheal stretching (TS).

Diagram of the measures taken from Quaker parrots. Figure from Ohms, et al., 2012.
Through observing the changes that occurred from the metal wires placed inside a Quaker parrot’s tongue and trachea while producing calls, researchers were able to conclude that a parrot's tongue functions much differently than a songbirds’. Even more amazing is that a parrot’s tongue is similar to a human tongue in the way that it is manipulated while producing sound. Researchers also determined that these parrots manipulate the sound frequency (pitch) of their calls by moving their tongues in and out. The researchers were also the first to observe a circle-like movement in the trachea that had not been described before in this species.

So whether my trouble-making parrot (you should hear him burp and excuse himself) is blowing me a kiss or mimicking a bird song, there are many similarities in the way that humans and parrots produce speech sounds. This is pretty amazing for two groups of animals that are so different!


Work Cited

Ohms, V., Beckers, G., Ten Cate, C., & Suthers, R. (2012). Vocal Tract Articulation Revisited: The Case of the Monk Parakeet The Journal of Experimental Biology, 215, 85-92 DOI: 10.1242/jeb.064717

2 comments:

  1. Nice work Porscha! Great job of pulling lots of information together in a small space.

    Dr. B

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