Evening star. [volume] (Washington, D.C.) 1854-1972, 1915-08-01

u tating in it's effect upon most
forms of life, has at least the virtue
of Iessening the death toll among the
birds, and the chief reason given for
this is the darkening or extinguishing
Of lighthouse beacons along the bird
routes or the lines of bird migration.
1t has been written by an English
authority that the mortality among
birds during the migratory period is,
indeed, amazing. 1t would be no ex-
aggeration to estimate that death takes
more than a fourth Of the birds bound
for British shores while they are still
on the wing. On the rocky lodges
around the great lighthouse at Ters-
chelling, Holland, as many as 1000 dead
birds have been found in a single
spring morning.
The lighthouse as a cause of the
Is well known in the United States.
Reference to this fact Is made by Wells
w. Cooke, assistant biologist in the
Department of Agriculture. in recent
pamphlet on Bird Migration" The
author, after assuring his readers that
"a fuller knowledge of birds has served
to increase rather than to lessen in
terest in the subject and that the
ton notes from more than 1000 diff
ferent observers, showing how wide
spread is the recent development of
this important phase of nature study"
The survey has been collecting data
on bird migration for more than
twenty-five years. The investigations
by it's field naturalists, extending over
Panama to the arctic circle, have re-
suited in voluminous notes, and in ad-
dition assistance of ornithologists
throughout the country has been en-
1so&4 re- 70
received in the spring and fall from
hundreds of experienced observers.
Lighthouse keepers have also sup
piled valuable information concerning
The facts gathered from the various
sources and from the largest amount
of data on bird migration ever col
lected in this country permit broader
and safer organizations saiisIa than nave
hitherto been possible.
Prof. Cooke also says that a knowl-
edge of the times Of migration of birds
is essential as a basis for intelligent
study of their economic relations. and
is equally necessary in formulating
proper legislation for bird protection
two subjects which form important
parts Of the work of the biological
survey
Prof Cooke is known by all the
nature students and others protesting
an interest in nature subjects in
Washington. being the leader of the
Audubon Society's bird walks. In the
introduction to his recent study on
the migration of birds he says that
it has proved a fascinating subject for
speculation and study from earliest
times. Long ago it was noticed that
birds disappear in fall and reappear
in spring, but not knowing where they
spent the intervening period, many
count for their disappearance. as
Information in hollow trees or In the
mud Of streams or ponds
Within the century, according to
Prof. Cooke, stories were current OF
whole flocks that were seen to disap-
pear beneath the waves Of the Medi-
terranean to winter in its depths. With
later years. however, has come
fuller knowledge of migration, espe-
cially Of the particular region in
season and more definite Information
in regard to the routes followed in
the spring and fall journeys,
The question, Why do North Ameri-
clusively answered, there being ad-
vanced two different and. indeed. dia-
metrically opposite theories to account
for the beginnings of these migrations.
PrO1. Cooke says tNdl dCCOIoiHs ~ tiAS
more commonly accepted theory the
United States and Canada ages ago
swarmed with flon-migratory bird life.
long before the arctic ice elds, ad-
vancing south during the glacial era,
rendered uninhabitable the northern
half of the continent. The birds love
of home Influenced them to remain near
the nesting site until the approaching
Ice began for the first time to produce
a winter-that is, a period of inclement
weather which 30 reduced the food
supply as to compel the birds to move
or starve. AS the ice approached very
gradually, now and then receding,
these enforced retreats and absences,
at first only a short distance and fer
brief time, increased both in distance
and duration until migration became an
integral part Of the very being of the
bird In other words. the formation OF
the habit of migration took place at the
same time that changing seasons in the
year replaced the continuous semi
tropical conditions of the pre-glacfal
eras. AS the Ice advanced southwark
the swing to the north in spring migra-
ton was continually shortened and the
fall retreat to a suitable winter home
heightened, until dur
ing the height of the glacial period
birds were for the most part confined to
habit of migration had been formed
and when the ice receded toward its
present position the birds followed 1T
s.sA in time established their
present long and diversified migration
routes.