Why do bird eat small pieces of stone?


The article is about the Gizzard an organ in birds which helps them digest food as they lack teeth. It also talks about other species who also possess it for different reasons,  their ancestral connection, and how it is also a popular human delicacy.


                                                       When we see a bird swallowing a stone, what do you think? are they gone crazy or it's just their natural instinct. It will make you think as to why an inedible non-digestible substance is swallowed whole by a bird. If we observe carefully birds do not have teeth and they swallow their food whole. In our mouth, we have teeth that are absent in birds beak. So, how do bird grind food which helps in enhancing the digestion activities? Small piece of stones to fill their Gizzard. The question arises, what is gizzard?  Gizzard also known as the ventriculus, gastric mill, and gigerium. It is an organ found in the digestive tract of some animals, some fish-like the mullet (Mugilidae) found in estuarine waters worldwide, and the gizzard or mud shad, found in freshwater lakes and streams from New York to Mexico, have gizzards, some crustaceans have gizzards but referred as a gastric mill, some annelids like earthworm have a gizzard, etc.. besides some birds.

                          Stone swallowed by crocodile for ballast.

Even fossils of some dinosaurs showed the presence of Gizzard stone pieces near it examples like Massospondylus, Sellosaurus, Omeisaurus, and Apatosaurus, etc. Gizzard is also seen in modern-day dinosaurs like the crocodile and alligators they swallow stone mainly for ballast and provide stability while in water like a ballast weight for cargo. Well its also a fact that birds evolved from dinosaurs and one of the Dinosaurs examples may be the ancestors of birds. One of the prominent examples of birds can be of an Ostrich that swallow stones or even small pieces of iron for the same reason that is digestion. Ostrich is also known as the greedy bird for the same reason.

                              Ostrich swallowing stone


What is Gizzard made of?

As I mentioned earlier it is a muscular organ Bird gizzards are lined with a tough layer made of the carbohydrate-protein complex Koilin, to protect the muscles in the gizzard. In certain insects and molluscs, the gizzard features chitinous plates or teeth. Koilin membrane is formed by secretion of glands, crypt, and surface epithelium, whereas Chitin is found as the primary substance in the exoskeleton of Arthropods and cell wall of fungi. So now you know how hard it can be compared to human nails.

Do, all birds swallow stones and grits for grinding their food?


No, not all of them swallow the stone. Carnivore birds like Vultures, Owl, and Eagles have a strong stomach acid which dissolves the whole prey. The Owl which swallows the whole prey spit the remains like fur, bones, teeth, feathers, and insect shells from that food in the form of a tight PELLET.

Gizzard in Cuisine

Poultry gizzard is a delicacy in many parts of the world. Grilled chicken gizzards are consumed in Haiti and throughout southeast Asian countries. Gizzard and mashed potatoes is a favorite diet of many European. 

                                                         So, what do you think about it now is it really a vestigial organ or really useful after knowing its benefit for both the animal worlds and humans. Also, now we all know that swallowing stone is not that pretty strange for a bird it is absolutely not a stuff for humans but for a bird this bizarre act is like a boon when you have no teeth.





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I am a voracious reader and just want to serve people with my writing.