Evening star. [volume] (Washington, D.C.) 1854-1972, 1906-12-01

would be at the southern end of the win
ter range. while those which had nested
near the middle Of the summer range would
hold middle position for the winter.
Normal Migration.
Mr.. Cooke refers to such a movement as
a normal migration, and gives, as an
example of a species performing it, the
lack-and-White creeper, which breeds from
South Carolina to New Brunswick. nest
ing In the southern part Of its range in
April. and in the northern part after the
middle of May, about fifty days being taken
to cross the breeding range. To quote Mr..
Cooke: If sixty days considered the
shortest possible time in which such a bird
can build nest, rear the young, mott and
be ready for the return Journey. then no
New Brunswick black-and-white creeper
is ready to start south before the middle
of July, the fifty days for the trip will
bring the earliest migrates to the gulf
states in September. Yet both old birds
and young of the year have been seen by
the midle of July at Key West. Fla, 500
miles south of the breeding range,
August 10 in Costa Rica, and on August Fl
on the northern coast of South America.
These dates prove conclusively that these
early migrants south of the United States
could not have been birds from the north
part of the range, but must have been
those from the southern part"
But many birds do not follow this nor
mall order of migration and others there
are which follow it only in part. Mary
land yellowthroats. Matched in Florida, re-
main there the year round, while those
which breed in New Foundland migrate In
the fall to the West Indies, flying right over
the winter range of their southern breth-
rem. The red-winged blackbirds of north
ern Texas migrate little, IL any, but those
which nest In the Mackenzie valley come
all the way down to spend the winter with
them. So it seems that. while there is a
general tendency in many birds to migrate
north In about the order in which they
spent the winter. and to winter in about
there is no hard-and-fast law concerning
such order. and 1t is not always possible to
determine a birds winter distribution by
knowledge of its summer range.
Relative Positions Change.
Then. spring migration differs materially
from fall migration. The so-called nor
mali migration Just referred to does not
take place in spring, since the birds Of a
given specie do not hold the same relative
positions throughout the entire northward
flight. 1t is supposed that in the case of
most species the first individuals to appear
In given locality are those which nested
there the year before; that these are fol-
lowed by the individuals which nested IN
the country Immediately to the northward,
which are In turn followed by those which
nested still farther to the north. Then
since. in some cases at least, the southern
nesting birds are the leaders both in the
spring and fall migratons. there must
necessarily be transposal Of relative posi-
ton between the time they leave US In the
fall and the time they come back to us in
the spring. 1t is not yet known where or
when this change in relative positions &C.
ours, but this point will doubtless be set
tied by further observation. Possibly the
more northern birds remain In winter quar-
tiers until the more southerly ones have
started north; possibly they all start to-
gether: possibly the more northern birds
start first, but very slowly, since their
country Is still ice-bound, and are passed
by the fast-hying southern birds. whose
nesting grounds are already open and wait
Ing for them. Later on, Of course, another
transposal must occur: that is when the
southern birds have settled down on their
pass over them in the wake of advancing
spring.
There has long been much speculation
concerning the speed at which birds per-
form their migratory journeys. and It has
recently been ascertained that in many
cases they travel some parts Of the Jour
ney very much faster than others Mr.
Cooke, treating Of this subject in his govern
ment report. states the migration Of the
black-poll warbler nicely illustrates this
variation in speed. He says: 1T winters
! in north central South America, and MI
CRATES in April across the West Indies to
Florida. From here, some individuals pass
on northwest to the Mississippi valley.
thence north to Manitoba, thence north
west to the valley Of the Mackenzie. and
thence almost due west to western Alaska.
From the Gulf Of Mexico to Minnesota, a
fairly uniform average speed Of 80 to IS
miles per day Is maintained; southern In
diana and Missouri are reached the first
week IN May, southern Iowa early in the
second week. and southern Minnesota is
entered by the middle Of the month. Then
comes squirt; within another week the
black-polls appear in the central part Of the
Mackenzie valley, and the following week
they arrive in northwestern Alaska, many
individuals undoubtedly averaging more
than 200 miles per day during the latter
part Of the journey. Thirty days are thus
occupied In travelling the 1000 miles from
the Gulf of Mexico north to southern Min