An Acorn Woodpecker was sitting on the Feather River levee road, and it was busy pecking at something. I stopped the car, since my viewpoint is to brake for animals, and the busy bird continued to eagerly seek whatever it was he saw.
Finally, I eased forward and the bird flew away. I pinpointed the spot where it had been and investigated. I expected to see termites, ants, or some delectable animal matter, but the gravely road was bare. There was only sandy particles, and then I deduced that stony silt was actually what the woodpecker was pecking. Grit for the gizzard! We forget that birds have no teeth and depend on an entirely different method of reducing roughage to digestible particles.
Grit! I immediately thought of Mother's chickens on the Missouri farm and the grit pail we kept full of crushed oyster shell. The commercial product was critical for digestion of grain and the odd assortment of things a chicken eats as well as for strong egg shell development. That gizzard was very apparent when we dressed (or undressed!) a chicken and found the tough organ full of stony particles and a yellowish secretion.
The chicken's gizzard contracts two or three times a minute with a grinding action, which can be heard with a stethoscope when coarse seed and grit are present. Grit, when added to the diet of a chicken, can increase the digestion of seeds and grains by ten percent.
On the farm, we served the gizzard along with the other parts, and when it was well cooked, there was a bite or two that was pleasantly tough and tasty. I suspect that much of the "clam chowder soup" in restaurants consists of minced chicken gizzards. Clams and gizzards have similar qualities.
I had to do a little refresher course on gizzards, and in the process, I discovered faded facts about the rest of the digestive system.
Most birds have gizzards the way that most birds have wings but not all! We remember the flightless dodo and ostrich to name a couple wingless types. Some tropical fruit eating birds have a straight track without a noticeable gizzard through which incompletely digested berries pass somewhat continuously.
The gizzard is primarily a muscular stomach organ used to crush foods to aid in digestion. The contracting power is remarkable in some of the larger seed eating birds, and glass objects can be pulverized, as shown in a turkey's digestion, and even lead items flattened by a force equal to a vice exerting 437 pounds of pressure per square inch!
Before food reaches the crushing machine, it goes down the esophagus, through the narrow glandular "proventriculus" stomach which produces digestive juices, and then into the gizzard. Some birds have a crop, a storage sac below the esophagus where surplus food is stored until ready for processing. The arrangement varies with different species, but all birds and mammals have the same basic digestive system design even man! We are indeed "hitched together." "Everything in the Universe is hitched together," as John Muir said.
The gastric acids are so powerful in some birds, such as birds of prey, that bones can be dissolved. Feathery and furry masses are clumped into a ball and regurgitated as a "pellet," a peculiar wad you can find in the woodlands, and wad detectives can analyze the contents to aid in revealing the diet of birds.
Peeking into the anatomy of birds can be an absorbing project, and before I was through with researching the gizzard, I ended up at the end of the digestive track which is called the cloaca. The word means "sewer" in Latin, and in light of the fact that digestive residue, urinary fluid, and reproductive exchanges all empty into the common tract, the combination is indeed remarkable.
One thing leads to another, and I reexamined the reproductive region as there is no certainty as to what goes on with mating birds even when you're observing. Their rear ends seem to connect, but not much can be seen except for ducks, and when waterfowl wed, the male's penile appendage is quite apparent. Watch! But most birds Do It by "cloacal kissing;" a function where sperm is simply expelled into that all versatile cloaca for transfer to the female. Now, in the wonder of wonders, out of that cloaca also comes the egg via the oviduct!
The biological intricacies merely indicate variations of a similar system used by all living species, and in that sense, we are indeed united in brotherhood on earth. As bird watchers, we mostly see the exciting color of feathers and interesting movements, and feel a great deal of satisfaction in recognizing species and making lists. But down under it all is the other dimension of physical structure and the adaptation of its abilities to the environment.
I have seen Mallard ducks waiting under oak trees in Oakland's Lakeside Park for the acorns to fall. It is incredible that they can consume those armored seed missiles, shell and all, and derive some type of nourishment from them. Yet, even the Band-tailed Pigeons and turkeys, among observed species, also gobble up whole acorns.
Turkey gizzards, in particular, can crush a pecan within an hour, and the stone-like hickory nuts are shattered in 30 hours. I have watched turkeys plucking acorns from the ground at Loafer Creek, and undoubtedly, the thin shell is pulverized in minutes. This gallinaceous bird was found to grind 12 steel needles to mush in the gizzard within 36 hours!!
Take a look at a bird's gizzard, and know that those "lower" feathered entities can do something humanity is quite unable to do!
© 2001 Rex Burress
April 16, 2001