Biology Reference
In-Depth Information
Q If penguins, which all live in the Southern Hemisphere, are so good at flying un-
derwater, why haven't any northern birds, such as loons or puffins, lost their ability
to fly?
A
This may be because Antarctica and nearby islands provide low, safe places for pen-
guins to nest, while Arctic islands are steep-sided, so oceanic birds in the north had to
nest on more inaccessible cliffs. Only one Northern Hemisphere marine species lost the
ability to fly: the Great Auk. This bird nested only on two or three low islands and be-
came extinct in the midnineteenth century.
Q Do birds sleep while in flight?
A
There'sevidencethatsomebirds,especiallylongdistancemigrantsandswifts,mayoc-
casionally sleepinflight.Birdsandmarinemammals aretheonlywarm-blooded animals
weknowofthathave“unihemisphericslow-wavesleep”—thatis,onesideoftheirbrain
may sleep while the other half is awake. Marine mammals apparently do this so they can
continue to swim and rise to the surface to breathe as they sleep. Birds on the ground can
sleepwithoneeyeopen,instantlyreactingtoapredator'sapproach.Thisabilitymayalso
allow them to sleep on the wing, which would be a handy skill for long-distance flights,
although so far no one has proven this using brainwave monitoring, either under laborat-
ory conditions or in nature.
The Highs and Lows of Flight
Q How high can birds fly?
A
ThehighestdocumentedbirdflightwasofagroupofBar-headedGeeseseenandheard
crossing the Himalayas from India to central Asia at 29,000 feet (8,839 m). A Mallard
was struck by an airplane over the Nevada desert at an altitude of 21,000 feet (6,400 m).
Tiny Blackpoll Warblers sometimes migrate as high as 21,000 feet on their 2,300-mile
(3,700 km) nonstop journey over the Atlantic Ocean. As far as we know, this is the
longest flight, both in distance and time, and the highest nonstop flight, of such small
birds.
