Biology Reference
In-Depth Information
capableofsustainedflight,thoughwildgallinaceousbirdssuchasturkeysandgrousecan
sometimes fly a mile or more before tiring.
The red fibers in “dark meat” are more useful for more purposes because they're cap-
able of sustained activity, but the trade-off is that they require more nutrients and a rich
supply of blood vessels. Since gallinaceous birds don't normally fly long distances any-
way, they're better off with the lighter, lower-maintenance white muscle fibers, giving
them white meat. Ducks and geese, which need to engage in both sustained swimming
and sustained flying, don't have white meat at all.
Domesticated chickens and turkeys have been bred to have a higher percentage of
white fibers in their white meat, as well as to have more meat in the first place. So Wild
Turkeys may have darker colored meat than do domesticated turkeys, but it's still con-
sidered white meat.
Q I'm pretty good at imitating bird calls, but there are some songs, such as the Wood
Thrush's, that I find impossible to whistle. I can't come close to imitating the shim-
mery, complex quality of its song. How does it do that?
A
Birds produce sounds with their
syrinx
(literally “song box”), which is situated at the
verybaseofthetracheaandthetopofthetwobronchialtubes.Bycontrollingthemuscles
of the syrinx, some birds can make one set of sounds with the left branch and a different
setofsoundswiththeright,producingharmonywiththeirownvoice.Themostcomplic-
ated sets of muscles in the syrinx belong to the thrushes, which is why so many of their
songs sound so ethereal.
Q I was amazed to read that loons spend the winter on the ocean. How can they sur-
vive — are they able to drink saltwater?
A
Yes, loons can drink saltwater when they are at sea because they have special glands
thatremovesaltfromtheirbloodstream.Whentheyhatch,loonsarefreshwaterbirds,eat-
ing freshwater fish and drinking fresh water — until their first migration. The moment a
loon gets a taste of saltwater, two glands near its eyes swell up and start removing excess
salt from the bloodstream. The salt is excreted in the form of thick tears or mucous via
the nasal passages. Our own bodies excrete excess salt by way of our kidneys and sweat
glands,andourtearsareassaltyasourbodytissues.Thetearsofloonsinwinteraremuch
saltier than ours, or than the loons' body tissues, because the excess salt is concentrated
before excreting. When loons return to freshwater in spring, their salt glands shrink for
the season. If a loon were to cry in summer, its tears would be no more salty than ours.
“A POEM IN BONE”
