Staunton spectator and vindicator. [volume] (Staunton, Va.) 1896-1916, 1907-02-08
WHY BIRDS MIGRATE.
A PROBLEM WHICH HAS NEVER BEEN
sATIsFACTORILY SOLVED.

r. PROBLEM WHICH HAS NEVER BEL
l.. SATISFACTORILY SOLVED.
q About this season there are likely
q be published newspaper accounts
: birds striking lighthouse in gre
q plumbers in a single night or perishir
i 10 sudden storm. These stories ca
j the attention of the public to the VOL
dsrful Journeys that great numbers {
birds perform semi annually.
For many years much careful dat
have been gathered on the matter i
which migration is performed, both b
the Biological Survey of the Unite
} s ates Department of Agriculture an
by independent observers. The Burea
OF Biological Survey has supplied al
observers who. were. willing to cooper
ate with blank schedules spring an(
aud fall. to be filled In with the date
Of arrival of each species, the number
first seen, the second date on which
tue species was seen, the date when 1t
became common, the date when 1t was
last seen Tin spring for species which
passed entirely through the locality to
more northern breeding grounds, and
in fall for migrants so passing any for
summer residents that 60 entirely out
of the locality for the winter). and some
other data.
These observations have established
the fact that the great majority Of
birds seen in any one locality during
the year perform northerly movement
in spring and a southerly movement
In fall, and that these movements are
OF considerable regularity as to date.
Unusually backward weather in spring
may retard migration, while cold and
stormy weather in fall has tendency
to acc celerate the movements Of south
ward journeying birds, but in average
birds the first appearance OF species
In spring or fall seldom varies much
more than a week. Ii was long sup
posed that birds which never entirely
disappeared from locality were only
partially or nonmigratory. For in
stance, in Southern New York and
New JERSEY the crow and the robin
are represented by some3s individuals
in most localities throughout the
year, and it was supposed that some
birds remained permanent residents
while the majority migrated. Ac-
cumulating data. however, have given
good reason to believe that the in
dividuals:seen in given locality in
winter are not the ones which bred
there, but are birds which having nest
ed farther north, have tgraduallY re
placed the summer birds in the fall mi
grafton, as the later moved leisureiy
South.
One of the features that has doubt
less added to the difficulties in pene-
trating the mysteries of migration Is
the fact that many birds migrating fly
chiefly by night. On clear nights these
migrating birds fly at such height that
their calls are but family heard. il at
all, By the alert watcher, while their
small forms are only occasionally seen.
Birds have been seen through tele-
scopes that were pointed at the faces
of the moon, crossing the range OF
vision at height Of mile or more.
On dark and cloudy nights they fly
much lower, and in storms are liable
to become absolutely bewildered, and
at such times they call constantly to
each other. Flying low on these
cloudy nights the birds are often dazed
by the lamps of lighthouse, and strik
ing against them IN great numbers,
are killed or manned.
All these things and many more OBJ
servation has taught;regarding migra
tion. As to it's causes, the best we can
yet do is to speculate. 1t was formerly
thought that u cold wave drove the
birds in fall to seek warmer climate.
while attachment to their summer
home impeIled them to Ieturn to IL viii
the comiug of mild whether again in
spring. 1t is reasonableIto believe that
attachment to given summer home
has much to do with the northward
spring Journey OF the birds, but 1t il
now generally conceded that insuffici'
eLcy of food rather than cold il The chief
factor that causes the return migration
in the fall.
Some of the hawks and other birds
repalr and reuse an old nest for many
years. When a pair of birds appear
at nearly the same date year after
years at given nesting site it reason
able to suppose that it is one and the
same pair, and that an attachment for
that particular site is indicated.
While we really see where birds as q
cla.s profit by migration, it is not easy
to understand how.certain individuals
are advantaged by it or what induces
those individuals to undertake it. To
explain this some ornithologlsts have
bro ught in the theory of the survival
of The ittest," arguing that such birds
as remained evercrowded in a south
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