The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1896-11-14
BIRD MIGRATION AND THE
WEATHER.
They Follow the Warmth and Are
Sensitive to Temperature.
From the London Spectator.

FROM lile LoLuOH spectator.
The results of eight years observation
Of the migration of birds into and out of
this country has just been issued by the
Council of the British Association 1t
appears opportunely, at the moment when
the rush of our summer birds southwark to
other lands is at its height, and the cor
responding stream of immigration from the
north is within few weeks of its greatest
volume The facts which it chronicles
are full Of interest, and though the author
of the report refrains from stating any
views as to the causes of migration, or the
intelligent forces which guide or suggest
the journeys of the birds, clue has been
found to account for the knowledge ap-
parently possessed by birds that on given
day, in distant and frozen regions, the
earth will be open and accessible. We
pass on to what seems to us TO be the most
interesting result of the present set of OBJ
servations Outside and inside the ring of
lighthouses the committee had another
body of information of the most important
kind. They had the weather chart at the
Meteorological Office If any one takes
the Times weather chart, and draws red
circle round the coasts of England, Ire
land and Scotland, this will represent the
ring of stations recording the arrival and
departure 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 feldfares 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 central part of that area.
The result is most suggestive. Nearly
the Oldest scientific notice of migration is a
note in the s'Floral Calendar of Theoph-
rastus, that the birds come to Greece on
the ''ornithian winds between February
20 and March H. As it was the oldest
so it is the longest lived of beliefs about
migration, that the birds wait for favoring
winds. The weather-chart shows that
they do not. The direction of the wind is
disregarded ''It is no incentive to mi
grafton On the other hand, heavy
gales stop migration entirely. The birds
dare not move, and the ocean species, such
as the petrels, 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 huuying cyclones
are crossing the Atlantic, or travelling
round the Shetland Islands and on to the
Norwegian coasts, the birds do not move.
1.-The stream of migration is damned up at
its source, and when released the birds
rush over in a torrent. The great congre-
gat1ons OF swallows noted at the end of the
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 September (Which
wrecked houses in Paris and Manchester)
were over. Since then the migration has
been normal and in smaller foeks So in
October, as soon as period of still, ''anti-
cyclonic 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-cyclonic' area in
Scandinavia has easterly 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 temperature
which is the main controlling factor in all
the great movements. Cold coming in the
calm anti-cyclone sends them south
Warmth, and rising thermometer, is the
instant signal to go north. A fact noted
by Mr.. Eagle Clarke shows the sensitive
ness of birds to the rise of temperature,
and the way in which, with their swift
fight, they follow the warmth as shadow
follows smoke. On February II, 1887,
wheat-ears and ring g-ousel were seen near
the Chicken Rock Lighthouse and the
Longship Station. This was strangely
early for these birds to come, but refer
ence to the daily weather report showed
that this portion of the British area was
the warmest spot in Western Europe on
that particular day