by John Shamgochian
The fecal sac: such a simple object.
It's a bag of mucous membrane for the waste of young birds. It's a
helping hand in the challenging duty of keeping a nest clean of
parasites. Just like responsible dog owners bag up their pet's waste, so do
the birds. But for birds, their young's
droppings come self-wrapped, a futuristic diaper, if you will.
I first discovered the droppings on May 4 as I sat on our back porch, escaping the chaos of our evening household. As I bathed in the evening tranquility, a House Sparrow fluttered down from the nesting cavity in our roof. In her beak she carried a white object, which she placed with care onto the branch of one of our two young apple trees. She sat there for a moment before bending down and carefully wiping her bill against the tree's smooth-barked branch. She flew back to her nest and was back a few minutes later with another of the objects which, like the time before, she similarly deposited onto the branch. It was only then that I realized what these things were: fecal sacs. As I had this revelation, I noticed how many of them there were. These bags of waste lined our tree's branches and our fence; although I have a slight tendency to over exaggerate, I must admit that the number of white blobs was quite impressive.
After the bird left, I moved in for a closer look. I was surprised to see that the sacs were more complex than I had expected. Each silky, white blob had a small, dark handle from which (I presume) the parent bird held the dropping. The next day, while I was taking a good long squint at the sacs, I was surprised to see a male sparrow land on our fence with what appeared to be a sac clutched in his beak. Up to that point I had only seen a female with the fecal sacs, with no sign of her mate. The bird sat there for a moment before carelessly letting the bag fall to the ground. It chose not to clean its bill as the female had but instead flew straight back to its nest hole in our roof, demonstrating the surprisingly opposite cleaning attitudes played out by human males and females.
Later I googled fecal sacs and found an article on Wikipedia (http://en.wikipedia.org/wiki/Fecal_sac).
I was amazed by how many curious behaviors revolve around that white
bag of ordure. Apparently the females of most species do remove the sacs more frequently than their mates, which would explain the obvious
inexperience of the sloppy male sparrow I had seen. Apparently young
birds release their droppings seconds after eating; if they do not, the
parents may commence to peck their cloacas to
stimulate release. Some
species will indicate if they're about to go. The Cactus Wren shakes
its body. The Curve-billled Thrasher points its back end skywards to
prepare the parents for the release of a white, slightly damp bag of
feces, neatly packaged and ready for immediate transportation, via beak,
to be politely dumped.
Oh, yes, and I forgot to mention that some hungrier parents will devour their young's feces with unusually disgusting gusto!
After a few hours the outer surface of the sacs seemed to dissolve and the young bird's waste sat there, unidentifiable from the droppings of their parents.
The life of the fecal sac: short but fascinating.
About the author: John Shamgochian, 13, is from East Providence, Rhode Island. His favorite birding spots include: "The Meadows" in Cape May, Plum Island in Ipswich Massachusetts, Monomoy in Chatham, Massachusetts , and Swan Point Cemetery in Providence, Rhode Island. John is one of The Eyrie's Student Blog Editors. Check out more of his writing on his blog: http://johnsbirdingblog.blogspot.com/.