Migration of Birds (1950)Lincoln, Frederick Charles
Science
Migration of Birds (1950)
Lincoln, Frederick Charles
Birds; Birds -- Migration
It has been claimed, with some reason, that small birds migrate
by night the better to avoid their enemies, and that most of the
nocturnal travelers are those that are naturally timid, sedentary,
or feeble-winged. To a certain extent this may be true as included
in this group are not only such weak fliers as the rails but also
the small song and insectivorous birds such as the wrens, the small
woodland flycatchers, and other species which, living habitually more
or less in concealment, are probably much safer making their flights
under the protecting cloak of darkness. Nevertheless, it must be
remembered that night migrants include also the snipe, sandpipers,
and plovers, birds that are always found in the open, and are among
the more powerful fliers, some of them making flights of more than
2,000 miles across the ocean.
Night travel is probably best for the majority of birds chiefly
from the standpoint of feeding. Digestion is very rapid in birds
and yet the stomach of one killed during the day almost always
contains food. To replace the energy required for long flight, it is
essential that food be obtained at comparatively short intervals, the
longest of which in most species is during the hours of darkness.
If the smaller migrants were to make protracted flights by day they
would be likely to arrive at their destination at nightfall almost
exhausted, but since they are entirely daylight feeders, they would
be unable to obtain food until the following morning. This would
delay further flights and result in great exhaustion or possibly
even death were they so unfortunate as to have their evening arrival
coincident with unusually cold or stormy weather. Traveling at night,
they pause at daybreak and devote the entire period of daylight to
alternate feeding and resting. This permits complete recuperation and
resumption of the journey at nightfall.
Public-domain text, read in full here on John Shaqi.
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