Avian Coprophagy

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The strange title is simply a euphemism for “birds eating poop.” You are familiar with bird poop as that white stuff deposited on car side view mirrors, pool decks, and window ledges, but new research reported in the National Library of Medicine provides a different way to look at it. Just as in our gut, the digestive system of birds contains a multitude of microbial flora and fauna that help in extracting energy from food and generally keep the digestive system healthy.

Green mini cooper car with bird poo on it to show an example of Avian Coprophagy

The early bird may get the worm, but eating feces may be more important. Over 40 percent of the world’s birds are migratory, so they face environmental challenges as they move from place to place and back again. Eating their own feces or the feces of other birds or even other animals helps birds change their gut microbial community to adapt to new foods and provides them with some nutrients as well. It may even protect them against diseases, although that is just speculation at this point. 

Birds have a highly specialized digestive system, refined over millions of years of evolution. After ingestion, food is broken down mechanically before reaching the stomach, where powerful acids and digestive enzymes partially break down complex carbohydrates, proteins, and fats. The partially digested food then moves to the small intestine for the absorption of nutrients. However, not all essential elements are absorbed fully during the first time through the gut. By consuming their own droppings, birds re-ingest the semi-digested food, giving their digestive system a second chance to extract valuable nutrients. This is a form of internal recycling, allowing birds to maximize their nutritional intake.

Young altricial birds in the nest produce “fecal sacs,” a membrane comprised of thick mucus, surrounding the broods’ excrement. A birdie “diaper,” so to speak. These fecal sacs are thrown out of the nest by the parents, keeping the nest free of contamination that might generate bacterial and fungal growth. The nest will also be less smelly and thus less likely to attract predators. Common Grackles even look for water into which they can dispose of the fecal sacs, so that no trace of smell is near the nest. (Sometimes, this behavior is to the chagrin of pool and bird bath owners.)

Some adult birds eat their hatchlings’ fecal sacs to extract the remaining nutrition in them. When the babies are only a few days old, their fecal sacs contain mostly undigested food that the parents take advantage of, but as the baby birds get older, they develop the bacteria that help them to digest food and the parents quit eating the fecal sacs because they contain less nutrition.

But not all birds produce fecal sacs. Bald Eagle and American Goldfinch young try to poop over the edge of the nest.

(By the way, of all organic fertilizers, bird droppings are the most valuable since their nutrients, in their effect on crop yields, are practically equal to those in non-organic mineral fertilizers. Bio Web.)

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