Biology Reference
In-Depth Information
Q How do bird intestines compare with those of humans? Are they longer or
shorter relative to their size?
A
Birds that eat nectar, soft insects, or meat usually have very short intestines, but birds
that digest grasses and other foliage or grain tend to have significantly longer ones. The
smallintestineofanOstrich,abirdthatgrazesongrassesandseeds,is46feet(14meters)
long, or double the length of a human small intestine!
Ofcourse,flyingbirdscan'tcarrymuchweight,andsotoreducetheweighttheymust
lug around, most food is digested very quickly and efficiently. Rather than keeping food
in the intestines for a long time, birds have a relatively huge liver (the heaviest internal
organ) and pancreas, both situated in the optimal place for a flying creature's center of
gravity. Both of these organs secrete juices that speed up the digestive process. What re-
mainsintheintestinesafterallthenourishmenthasbeenabsorbedentersthebird'scloaca
to be ejected when the bird poops.
The seeds of berries eaten by young Cedar Waxwings appear in their droppings just
16 minutes later, and seeds of elderberries eaten by thrushes pass through the digestive
system in a mere 30 minutes. A Northern Shrike can digest a mouse in 3 hours, while
the “bearded vulture” or Lammergeier of the Mediterranean (related to North American
hawks) can completely digest a cow vertebra in a day or two.
Q Why is bird poop white?
A
You may not care to examine bird droppings too closely, but if you do, you'll see
they'reusuallymadeupoftwodifferentcomponents.Thebrownishordarkgreenishpart
is the fecal matter, or the poop. This is what remains after food has gone through the en-
tire digestive system. The white part is actually urine.
Our urinary system filters our blood of impurities, which build up even before birth.
Mammals eliminate these wastes as urea, a clear, yellowish fluid that is highly toxic and
must be diluted with huge quantities of water. Birds and other animals that hatch from
eggs eliminate the wastes from their kidneys as uric acid, a substance that doesn't need
