Let’s Hear It for Honking Swans!

A trumpeter swan is known for it's loud "honk."

A trumpeter swan is known for its loud “honk.”

In my job, it is important for me to know the anatomy of many different kinds of animals. I encounter many different species on a daily basis, and I investigate them inside and out to uncover diseases, trauma, or geriatric (old age) changes. Sometimes the anatomy I see is downright amazing! Here is just one example, and it has to do with the “songs” of some of the largest birds in our collection.

Clues to the types of sounds birds are able to produce can be found by looking at their trachea, or windpipe. At the base of the trachea just before branching into the lungs is the bulbous syrinx. In combination, the trachea and the syrinx allow birds to create complex songs of chirps, whoops, whistles, or any other combination of sounds. In most birds, just like our own windpipe, the trachea is a simple, straight tube leading air to the lungs. But some groups of birds have elaborate tracheas with loops, curves, and incredible length.

The loud, raspy, nasal “honk” of a trumpeter swan is easily recognizable, even in an aviary full of dozens of different species singing. Though it’s not necessarily the most beautiful melody in the bird world, the swan gets a particular point across—“HONK! I am big, loud, and you’d better stay out of my way!”

Swans and cranes have an extra-long, looping “S”-shaped trachea that starts at the top of the neck, extends deep within the chest, takes a 180-degree turn, continues back to the collarbone, takes another 180-degree turn, and at the syrinx it ends up branching to the lungs. That’s quite a journey for air! But it may be part of the reason why these birds can be so noisy—hence the names whooping crane and trumpeter swan.

The amazing elongated trachea of a loud bird like the swan and crane is one of the many remarkable adaptations I get to see on the job.

Rachael Holland is a research technician in the Wildlife Disease Lab, San Diego Zoo Institute for Conservation Research. Read her previous post, Priceless Avian Gems: Blue-Chinned Sapphires.