Screamers: Skeletal Anomalies

Summary: Can Screamers get any stranger? You bet! Join Kiersten as she discusses some skeletal anomalies that Screamers possess.

 

For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean

 

Show Notes:

“Functional significance of the uncinate processes in birds”, by Pete G. Tickle, A. Roland Ennos, Laua E. Lennox, Steven F. Perry, and Jonathan R. Codd. The Journal of Experimental Biology 210, 3955-3961. 2007 doi:10.1242/jeb.008953

“Uncinate processes in birds: Morphology, physiology and function,” by Jonathan R. Codd. Comparative Biochemistry and Physiology Part A: Molecular and Integrative Physiology, Vol 156, Issue 3, July 2010, 303-308.

Britannica: Screamers, https://www.britannica.com

Music written and performed by Katherine Camp

 

Transcript

(Piano music plays)

Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

(Piano music stops)

Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

Episode six of Screamers is going to take us on an interesting journey into  Screamer anatomy because the sixth thing I like about screamers is their weird anatomical quirks. Last episode we talked about one of their special anatomical accessories, the spurs. In this episode we will look at two more of the Screamer’s anatomical anomalies that also pertain to the skeleton.

Many of you have probably heard somewhere that birds have hollow bones. This is a simplified statement about bird bone anatomy. We will need to understand this a bit before we talk about screamer bones, so, those of you that already know this, bear with me, for those of you who are hearing this for the first time, hold on to your hat, I’m about to blow you mind.

Vertebrate skeletons are made up of hard, calcium rich bones. It’s what give our bodies their shape and ability to move. Birds are vertebrates so they rely on their skeleton to give their body shape and act as the anchor for muscles to allow them movement, just like mammals. Avian bones are special because they have adapted to the bird’s need to fly. If you have too much weight defying gravity can be difficult. Flighted birds adapted to this challenge by evolving less solid bones than mammals. 

Using the word hollow, makes you think of a tube, such as a straw or toilet paper tube that is completely open inside with no internal structure. You can look through one end and see clearly out the other end with no obstacles. Bird bones are not hollow in this manner. Their bones have an internal structure throughout the tube. If we were to look inside a bird’s bone we would see more of a honeycomb design. It’s essentially bones with air pockets. These are called pneumatic bones. 

The bones have lessened weight by getting rid of dense material but have increased strength by adding structure throughout the middle of the bone. This is how flighted birds can get off the ground and fly. They have bones that contain more air that provide structure for the body and muscles without being so solid that flying is a struggle. 

Now having said this, if we look at an average flighted bird, say a Bald Eagle or a Northern Cardinal, not all of their bones have this honeycomb structure. Typically, the larger bones will have this structure and smaller bones will not. The smaller bones will be more solid. This is where the Screamer skeletal oddity applies. All the bones in a screamer have this open honeycomb structure. All of them, including the smallest toe bone. Screamers have the most pneumatic skeleton of any living bird. And we have no idea why. 

Screamers are good flyers. Once they get up into the air, they soar like vultures, riding the thermals. They can soar for hours at a time, but as we know they spend most of their time on the ground in or around water. They are a larger bird, so maybe this has to do with their interesting bone structure. On the other hand, geese and swans are the same size, are great flyers and spend most of their time on or near the water, but they do not have this skeletal anomaly. 

This is not the only abnormality about the Screamer skeleton. Another oddity sets Screamers apart from almost all other birds. This interesting tidbit involves the uncinate processes. As before, we need to do a short anatomy lesson to fully understand the anatomical oddity of the Screamer. 

The uncinate process is a bony projection that is attached to vertebral ribs in avian skeletons. These projections are important in avian respiration. Birds do not have a muscular diaphragm like mammals to help them inflate and deflate the lungs. Birds rely on the movement of their sternum to breathe. That’s why it’s so important to hold birds properly when restraining them for veterinary care or scientific measurements. If you put too much pressure on the sternum, you can suffocate them. 

Studies have shown that the uncinate processes are integral in avian respiration acting as attachment site for muscles used in the mechanics of breathing. The presence of an uncinate process on the ribs of a bird increased the respiration function by 2 to 4 compared to a bird without an uncinate process. These processes allow the bird to more easily rotate the dorsal ribs forward, pushing the sternum down and inflating the lungs. Seems pretty important to me!

The length of the uncinate process varies by species and seems to be impacted by what physical activities the bird partakes in most often, for example walkers versus divers versus non-specialist birds.

Further studies have shown that the uncinate process is actually important in both inhalation and exhalation in birds. I don’t think I need to tell you this, but this little bone extension seems like a mighty useful tool and one that all birds should have, but the title of the episode isn’t Screamers: Skeletal Normalities but Screamers: Skeletal Anomalies. 

So, here it is folks. Screamers do not have uncinate processes. That’s right, they do not have these little bones that are so helpful for breathing. And once again, we don’t know why. None of the three species of Screamers have uncinate processes. They can breath, clearly they are living creatures that process oxygen just like the rest of us, but unlike most species of birds they do not utilize uncinate processes to do it.

Every episode I write about these incredible birds makes me like them more and more. I hope you think so too because my sixth favorite thing about Screamers is their skeletal anomalies.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

Join me next week for another exciting episode about Screamers.  

    

(Piano Music plays) 

This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.