The Devils Lake world and inter-ocean. (Devils Lake, N.D.) 1915-1920, 1915-04-08


only after experience through many
generations had proved It's advantage
eS.
There are some Who argue that love
Of birthplace is the impulse which
causes spring migration, and these
call attention to the seeming impa-
tience Of the earliest arrivals. Ducks
and geese push northward with the be-
ginning Of open water so early, so far,
and so fast that many are caught by
storms and wander d~isconsolately over
frozen ponds and rivers, preferring to
risk starvation rather than to retreat.
The purple martins 'often arrive at
their nesting boxes SO prcmaturely
that the coy home becomes a tomb if
a sleet storm sweeps their winged
food from the air. The bluebird's
CHEEKY MARBLE we welcome as q har-
binser Of spring, often only to
find later a lifelcss body in some shed
or outbuilding where the bird sought
shelter rather than return to the sun
ny land so recently left.
AS a matter of fact, however, only
a small percentage of birds exhibit
these migration propensitites. The
great majority remain in the security
OF their winter homes until spring is
SO far advanced that the journey can
be made easily and with comparative
ly slight danger, and they reach the
nesting spot when the food supply is
assured and all the conditions Of the
weather and navigation are favorable
fer beginning the rearing OF q family.
Breeding Instinct Governs Return.
1t can be safely said that the weather
in the winter home has nothing TO do
with starting birds on the spring mi
grafton, except in the case of q few,
like one Of the ducks and geese,
which press n0rthward as fast as open
water appears. There is no apprecia-
bic change in temperature to warm
the hundred OF more species OF our
birds which visit South America in
winter that it is time to migrate. 1t
must be d force from within, a physio-
logical change warning them Of the
approach Of the breeding session, that
imlpe's them to spread their wings fer
the long flight.
The habit Of migration has been
evolved through countless generations,
and during this time the physical
structure and habits of birds have
been undergoing a process Of cvolu-
ton in adaptation to the climate of
!; the sumner homie, In spring and
early umlme climatic conditions arc
decidedly variable, and vet there must
be some period that has on the aver
age the best weather for the birds ar
{ rival. IN the course Of ages tb>Es
/: have boon developed habits Of migra-
ton, "n1er the infinon~c Of which the
bird So performs its y l&rato,y move,
mcntS that on the average it arrives a
= the nesting site at the proper timc.
Local Weather Conditions Mi.tor
Factors.
: Local weather conditions on the DAY
of arrival at any stated locality arr
minor factors in determining the ap
pearance Of a given species at tina
time and place. The major factors il
the problem are the weather condition
far to the SOUTHWARK where the nigh
lights began, and the relation whicl
: that place and time bear to tic ave-
age position CT The bird under norma
weather conditions. Many: If 10
most. instances of arrivals Of bird
0:dcr adverse weat!.e. coaui,jors al,
probably explainable ny the supposi
ton that the flight began under favor
able auspices and that later the wealth
en- changed. Migration in spring US
ually occurs with a rising tempera
ture and in the autumn with a fallin,
temperature. In each case the chang
ing temperature seems to be a NOR
potent factor than the absolute degre
of cold.
The direction and force of the wind
except as they are occasionally init
mately connected with sudden and ex
n IRENE variations in temperature, seer
2 to have only a slight influence on mi
. grafton.
Most Birds Migrate at Night.
Some birds migrate by day, bu
most of them seek cover of darkness
Day migrants include ducks and gees
(Which also migrate by mighty, hawk
swallows, the nighthawk and tn
chimney sweep. The last two, CON
bining business and pleasure, cate
their morning or evening meal durin
a zigzag flight that tends in the dc
sired direction. The daily advance Q
such migrants cover only a few mile:
and when a large body of water is er