Screamers: Eyes and Beak

Summary: Join Kiersten as she talks about the eyes and beaks of the Screamer.

 

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

 

Show Notes:

Ornithology 3rd Edition by Frank B. Gill

“The evolutionary relationship among beak shape, mechanical advantage, and feeding ecology in modern birds,” by Guillermo Naval, Jen A. Bright, Jesus Marugan-Lobon, and Emily J. Rayfield. Evolution 73-3;422-435, Society for the Study of Evolution. doi:10.1111/evo.13655

“Bird Eye Color: A Rainbow of Variation, a Spectrum of Explanations,” by Eamon C. Corbett, Robb T. Brumfield, and Brant C. Faircloth. Https://doi.org/10.1111/ibi.13276.

Music written and performed by Katherine Camp

 

Transcript

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

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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.

This is the penultimate episode of Screamer and the ninth thing I like about this animal is their eyes and beaks. One of the things that is often overlooked in bird is their eye color, so today we will delve into the variations that exist by looking through the eye of the Screamer. Bird beaks, or bills either is correct, also vary extensively through out the avian family. Beak shape often indicates what type of food the birds eats, but like everything else about the Screamer, things are not always as they seem.

Bird eye color varies more than anyone expected. Not many researchers have attempted studying this characteristic and the few that have taken up this research topic and finding more questions than answers. Colors ranged form dark black or brown to vivd emerald green, sapphire blue, scarlet and crimson, turquoise, and even white. There is even a bird with pink eyes. It is absolutely amazing the various hues that birds’ eyes contain. 

Irises can be one color or more than one. The eyes of Rock Pigeons, one of the most disliked birds around the world, are bicolored starting with a ring of yellow on the outside and red/orange close to the pupil. The Satin Bowerbird has eyes with a vibrant blue ring on the edge of eye with an equally vibrant ring of purple next to the pupil. The Three-streaked Tcharga has a ring of light spots that look like stars set in a dark background giving them some of the most unique bird eyes around. 

Eye color in birds can change as a bird matures, for example Osprey eye color changes from red as juveniles to yellow as adults. Sexual dimorphism is also present in some species of birds meaning the female’s eyes are a different color than the male’s. Seasonal changes in eye color can also happen, for example Brown Pelican eyes change from brown to blue during breeding season.

Southern Screamers and Northern Screamers both have brown eyes as adults, while Horned Screamers can have yellow to orange to red eyes as adults. To clarify, I found no research indicating that these birds eye color changes as they age, but I could only find reference to their adult eye color. 

There are three things that contribute to the color of a bird’s eye, pigments, blood vessels, and structures. These three color options are still being closely studied but certain pigments are responsible for light colors and different pigments are responsible for darker colors. For example, carotenoids are responsible for the orange color of birds in Family Anatidae which includes certain ducks. An increased amount of blood vessels in the eye creates the red eyes of some species. 

Why do bird have such varied eye color? The short answer is we just don’t know. It could be related to how they find food, where they nest, diurnal versus nocturnal behaviors, communication, or another reason we have not thought of yet. Much more research needs to be done to answer this question, but for now, we can marvel at the extreme variation of bird eye color. 

Now, let’s take a look at some bird beaks. Just like eye color bird beaks vary tremendously. They can be wide and flat like a duck, tweezer-like similar to a gnatcatcher, chisel-like as the raven’s beak, long and thin like a hummingbirds, and deeply curved like the honeycreeper. These are only a few beak shapes found in the avian world. What a bird eats can impact the shape of its beak. Keeping this idea in mind, let’s look at the Screamer’s beak.

Screamers eat leaves, stems, flowers, and roots of aquatic vegetation, so we might assume t