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Avian Digestion

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What happens to food after a bird swallows it? It may be stored in their crop, a pouch which is actually an enlarged part of its esophagus that some species of birds (and bees, fish and earthworms) have, or it may go directly to their stomach.  Birds have a two-chambered stomach.  The first chamber, the proventriculus, secretes acids that help break down food, including bones. A shrike’s well-developed first stomach chamber can digest an entire mouse in only three hours!  From the proventriculus the food goes into the second chamber, which is referred to as the gizzard, before entering the intestines.  The gizzard is a muscular organ which grinds up tough food, sometimes with the help of grit that some birds ingest.  The gizzard grinds the gravel and stones against the nuts and seeds, a process which smashes the food.  Wild turkeys can actually pulverize walnuts in their gizzards!  In some species, the gizzard remains small and insignificant during the summer when their diet consists of soft food such as flesh, insects, or fruit, but it grows more powerful during the winter when seeds are their main food.

6 responses

  1. Kay Shumway

    How did you get those wonderful shots?you are amazing!

    October 25, 2012 at 12:31 pm

    • Clyde Jenne

      Smith & Wesson!

      October 25, 2012 at 1:19 pm

      • Very funny, Clyde! Let me know if your trees have any visitors, please!

        October 25, 2012 at 2:58 pm

  2. Wow – that is incredibly cool. I’ve always been amazed by what our ducks and chickens can eat, but didn’t know the particulars of how their crops and stomachs worked. Once a neighbor’s cat caught a baby mole, left it in the field at our feet, and then one of the ducks waddled up to us and gulped it down, much like the robin with the berry in your photos.

    October 25, 2012 at 2:24 pm

    • That’s amazing, Kellyann. I wouldn’t have guessed that a duck would dine on a mole!

      October 25, 2012 at 4:34 pm

      • I can attest to it as an eye-witness. We were all rather startled too! But I’ve also seen them eat live frogs, which were easily larger than that baby mole.

        Still, it feels odd… definitely an abnormality in the food web. It did require inter-species cooperation, after all, in which cat catches mole, is chased off by humans, who dither over what to do with such a helpless orphan, not noticing the duck wandering by until it resolves the dilemma in an unexpected and vaguely unsettling way.

        October 25, 2012 at 5:39 pm

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