Biology Reference
In-Depth Information
pattern, with something that looked like a serrated diamond pattern in the center.
What was that?
A Many young birds, including robins, have mouths that are brightly colored on the in-
side. The color helps stimulate their parents to feed them when they open their mouths.
On the roof of the mouth, you saw the opening to the bird's nasal passages and its Eus-
tachian tubes. When birds breathe through their nostrils, the air flows through the nasal
passages to the glottis , a fairly large opening on the bottom of the bird's mouth where the
trachea begins.
Q Birds don't have teeth, do they? How do they chew their food?
A You'reright,birdsdon'thaveteeth. Theyusetheir bills tohandle andprepfoodbefore
they eat it, but they don't actually need to chew their food before swallowing it. Hawks
use their sharp bills to rip apart prey,then swallow chunks ofmeat. Finches and sparrows
usetheirbillsasanutcrackertoopenhard-shellednutsorseeds,whichtheythenswallow
whole.Birdsthateatseedscanhavemanysmallmucousglandsinsidetheirmouthtohelp
them lubricate the seeds before swallowing, and salivary glands that secrete enzymes to
begin the digestive process.
Wehumanshaveagagreflexthatusuallypreventsusfromswallowinglargeitemsun-
til they've been pulverized by our teeth. But even fairly small birds can swallow chunks
so big they'd make us choke. A tiny Saw-whet Owl has no trouble downing a whole deer
mouse, and a Great Blue Heron can swallow huge fish whole. Birds that eat small food
particles, suchasinsect eaters, mayhaveafairlynarrowesophagus,butthosethateatbig
chunks have an extensible esophagus that stretches to accommodate the food; the skin of
their neck is equally stretchy.
Q I understand that “bird's nest soup” is a delicacy in Chinese cuisine and that the
nests are made of saliva. Is that true?
A Yes, the nests used in soup are constructed by Asian swiftlets whose gluey saliva
hardensintoacup-shapednest.ThemostheavilyharvestednestsarefromtheEdible-nest
Swiftlet and the Black-nest Swiftlet, found mostly around the coasts of southern China
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