The Prince George's enquirer and southern Maryland advertiser. (Upper Marlborough, Md.) 1882-1925, 1896-11-27
BIRD MIGRATION AND THE
WEATHER.

The results of eight years observa-
tion of the migration of birds into and
out of this country has just been is
sued by the Council of the British As
sociation. 1t appears opportunely, at
the moment when the rush of our sum-
mer birds southwark to other lands is
at its height; and the corresponding
stream of immigration from the north
is within a few weeks of its greatest
volume. The facts which it chronicles
are full of interest, and though the au-
thor of the report refrains from stating
any views as to the causes of migra-
tion, or the intelligent forces which
guide or suggest the journeys of the
birds, clue has been found to account
for the knowledge apparently possessed
by birds that on a given day, in distant
and frozen regions, the earth will be
open and accessible. We pass OH to
what seems to us to he the most inter-
esting result Of the present set of obser-
vations Outside and inside the ring
of lighthouses the committee had an
other body of information of the most
important kind. They had the wealth
er chart at the Meteorological Office.
If any one takes the Times weather
chart, and draws a red circle round the
coasts of England, Ireland and Scot
land, this will represent the ring of
stations recording the arrival and de-
parture of the birds. Outside this IS
wide region, from the North Cape to
the top Of Corsica and the Pyrenees,
over which our Meteorological Office
daily notes the weather in its chart.
Thus, when the gray crows and field
fares are arriving at Sandringham, we
know exactly what the weather was
like in Norway when they started, and
over the North Sea when they were
flying. So we know what the wind,
barometer and temperature were like
in France when the flights Of spring
migrants reach the Start. In this
double record we can compare both the
daily weather of North Europe and the
daily movements of the birds in cen
trail part Of that area.
The result is most suggestive.
Nearly the oldest scientific notice of
migration is note in the ''Floral Cal
endar" of Theophrastus, that the birds
come to Greece on the ''Ornithian
winds" between February 20 and
March IL. As it was the oldest so it
is the longest lived of beliefs about
migration, that the birds wait for IA
voring winds. The weather-chart
shows that they do not. The direc-
tion of the wind is d,sregarded. "lt is
no incentive to migration" On the
other hand, heavy gales stop migration
entirely. The birds dare not move,
and the ocean species, such as the pet
rels, are caught and driven inland in
heavy gales. Ordinary steady winds
they simply disregard. In other words,
what the birds observe is not wind, but
weather" When the hurrying cy-
clones are crossing the Atlantic, or
travelling round the Shetland Islands
and on to the Norwegian coasts the
birds do not move. "The streams of
migration is damned up at its source"
and when released the birds rush over
in a torrent. The great congregations
of swallows noted at the end ofthe first
fortnight of September, not only on
the Thames eyots, but on the Rhine.
had been waiting until the cyclonic
gales of the first fortnight of Septem-
Der (Which wrecked houses i'm Paris
and Manchester) were over. Since
then the migration has been normal
and in smaller flOckS. So in October,
as soon as a period of still, "anti-cy-
clonic weather." with cool temperature,
begins in Norway, the birds set out
for England. They come here on an
easterly wind, not because they started
with it, but because the calm "anti-cy-
clonic" area in Scandinavia has easter
ly breezes on its edge where it lies over
the North Sea. If it is not wind which
the birds wait for, we may ask what
other weather conditions beside the
absence of storms is an incentive to
migration. The answer given by the
charts is temperature. 1t is tempera-
ture which is the main controlling fac
tor in all the great movements. Cold
coming in the calm anti-cyclone sends
them south. Warmth, and a rising
thermometer, is the instant signal to
90 north. 4 fact noted by Mr.. Eagle
Clarke shows the sensitivenees of birds
to the rise of temperature, and the way
in which, with their swift flight, they
follow the warmth as Il shadow follows
smoke. On February II, 1887 wheat
ears and ring were seen near
the Chicken Rock Lighthouse and the
Longship Station. This was strange
Iv early for these birds to come, but a
reference to the daily weather report
showed that this portion of the British
area was the warmest spot in Western
Europe on that particular day-Lon-
don Spectator.