The digestive system of birds compares to humans only to the esophagus.
After that, birds possess a variety of different designated areas, where a complex combination of processes work together to break down the food consumed.
One such organ in birds is the gizzard also known as the ventriculus or the gastric mill, which is a specialized stomach-like organ found in their digestive tracts that helps them in grinding their food down.
Bird’s digestive tract and the processes are fascinating, especially when you look at how different birds utilize what appears to be the same thing in wondrously different ways.
So today we will go through the digestive tract and the gizzard in particular, and also look at how different birds eat and digest their food.
Bird’s Inside Structure – A Crash Course
The main or ‘true stomach’ of birds is called Proventriculus. It is located between the esophagus and the gizzard and is a glandular organ that is rod-like in structure.
Just like in the human stomach, the primary responsibility of this organ is to secrete hydrochloric acid into the digestive compartments where it churns the materials ingested and commences the digestion process.
After the proventriculus, comes the gizzard which is also known as the muscular stomach, which is where the “chewing” happens.
This is extremely useful for birds who cannot chew bigger foods down because they do not have teeth like mammals.
One of the most fascinating aspects of this already miraculous organ is what is referred to as gastroliths or gizzard stones. And yes, the name is quite literal.
Birds swallow tiny bits of stone and gravel that then travel to the gizzard and act as teeth.
These “teeth” thus aid in digestion and it helps in fragmenting and breaking down harder seeds that the bird cannot chew!
Bird gizzards are also protected by a thick layer of koilin, which is a tough substance made of 90 percent protein.
With time though, these gizzard stones become smooth and rounded because of the polishing from the hard substances it has to grind down.
Once they get too smooth and cannot attain their purpose, they are either thrown up and out or excreted.
Do All Birds Have Gizzards?
Yes, all birds have gizzards, though how much they utilize them and their physical dimensions depend on the feeding pattern of the species.
For instance, in species like ducks and gallinaceous birds, like turkeys, quails, and grouse, the gizzard is very thick and muscular.
If you look at these birds’ appetites, it becomes evident why. These birds eat nuts, and hard seeds as their main food source and thus need the breaking down of the action of gastroliths for proper digestion.
Other birds, especially those who consume softer feed like soft-bodied insects, fruits, or just nectar have gizzards with very thin walls that are small.
Owls, on the other hand, tend to swallow their small prey whole, and so the digestion process is both fascinating and a little grotesque.
In both of their stomachs, the glandular and the muscular, soft tissue of the swallowed prey is digested and liquified.
Harder substances like bones, teeth, and feathers all travel to the gizzard, where the organ then works at contracting and squeezing out all the rest of the remaining liquid into the intestines. Finally, the non-digestible parts are coughed up.
Are Birds The Only Animal With Gizzards?
No! Many other animals from different classes also have gizzards.
In the mammalian family, pangolins also known as scaly anteaters possess gizzards as they lack teeth and need the help of gizzards to grind their food. Crocodilians like alligators and crocodiles have gizzards.
Many fish species like the mullet, the mud shad, and the gillaroo have gizzards. In the Crustacean family as well, there are many who have gizzards though in their case it is referred to as gastric mills.
Another animal that has gizzards is earthworms. A fun fact for you, based on fossil fuel estimation, it is believed that many species of dinosaurs also had gizzards!
Does A Crow Have A Gizzard?
Yes! All birds, from ostriches to hummingbirds, and that includes crows as well, have gizzards. They are notorious for swallowing stones and gravel and using them in their tough, muscular gizzards.
They carefully search for the right stone, one that is flat but sharp enough at the edges to help their purpose!
Do All Birds Have Gullets?
One part of the digestive tract that we did not talk about in the crash course was the crop or gullet of birds, which is a sac-like organ that is responsible for storing the food before it is passed on to the glandular and muscular stomachs for breakdown and further processing.
As opposed to gizzards, not all birds have gullets. Vultures are one of the most famous birds who use their gullets, storing up food when prey is abundant and lazily lying around to digest the food later on!
Do Eagles Have Gizzards?
Yes, eagles have evolved to have a part of their digestive tract developed into a gizzard and help them break down larger harder substances before their strong stomach acid can digest them. Gizzards are also the place where pellets form.
Do Snakes Have Gizzards?
No, snakes do not have gizzards. Their j-shaped stomach is where most of the digestive processes happen.
The proteins in their food are broken down by the enzymes and other gastric juices secreted by the stomach cells. The food is then passed to the small intestine, where absorption of nutrients takes place.
Birds might be small and puny, but the processes and capabilities it undertakes as a result of evolution are a true spectacle of nature.
Hope you had fun exploring their feeding habits and more importantly, we hope you learned something new today!
Thank you for reading!
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