A small grebe and a big fish.

I was fortunate enough to come across a pied-billed grebe that had just caught quite a prize. A fish, perhaps a third of the length of its captor, was being cleverly manipulated into an injestable position. It amazes me how such a small bird can capture, handle, and consume such a relatively large fish.

I suppose it has something to do with the remarkable digestive system all birds possess. Birds, such as herons, grebes, and fish-eating ducks consume their prey headfirst. Since this is usually not the original position of the soon-to-be-eaten morsel, a deft manipulation and tossing process soon puts it in the right position. The mouth is far larger than what the size of the beak would suggest and opens broadly to accept the slithering meal. Down the wildly expandable oseogophus to what is sometimes called the first stomach, the proventriculus accepts the fish and starts the process of digestion. Strong acids and enzymes work their magic here. If the creature wasn't dead heading down into the gullet, it soon will be.

Not all birds have a crop, an expansion of the esophagus before the "first stomach." Its function, if it exists at all in grebes, is certainly limited. After the proventriculus comes the gizzard or "second stomach." The reality is that both these organs are often housed together in the same mesenteric mass and may be collectively called the stomach. Gizzards are very important in birds eating hard vegetable matter such as seeds and nuts, they have a much less significant purpose in fish-eating species.

Although large, fish are actually easier to digest than plants. Cellulose, an indigestible and difficult to penetrate the protective coating of the plant cell, require strong crops and long intestinal tracts to properly digest. For this reason, birds that are herbivorous in nature have longer small intestines than carnivorous ones. Grebes have only a short length of small intestine which is still enough to absorb a digested meal it forced down earlier.

An interesting fact about all grebe species is that they eat feathers. It is thought that the feathers form a plug between the gizzard and the small intestine that allows a more thorough digestion of harder fish bits such as the bones. They also act as a means of reducing the number of parasites living in the proventriculus. When digestion is completed they will expel the undigested feathers as a pellet, similar to what owls do. To see some excellent pictures on this, go to this website.

One of the reasons I write blogs is to learn things I have never known or have long forgotten. Today's blog was no exception as I uncovered some fascinating facts about grebes. I hope you enjoyed reading it as much as I did writing it.

Thanks for reading.     Ericspix     Eric Svendsen