The Superior times. [volume] (Superior, Wis.) 1870-1912, 1894-07-21
BIRDS METHODS OF STEERING
Some Problems as Yet UnsoIved by
Science

Some Problems as Yet Unso1ved by
Science.
The flight eff birds still presents sew
eral unsolved questions. How they
steer has never been fully explained.
With the naked eye, or. better still,
with field glass. many of them can
the left or right side. according to the
directions in which they wish To 90.
This use Of the tail as ruddcr is much
practiced by pigeons, jackdaws rocks,
laikS swallows. hUuse-martinS. sand
Martins, and, l believe. by most of our
common birds. Gulls let down foot
on enc side or the other. and. no doubt.
many Ctiier web-footed birds do the
same. StlIl a rock or pigeon that has
lost lis tail marriages to steer Wei. the
chief result of the loss being that he
cannot stop suddenly or feat upon the
air, but must take rapid strokes with
his wings. What other method. then.
has the bird of stcer ring: One fact
that bears upon this question can be
easily observed When a bird wishes
20 turn TO the left he moves the CEN
Ter Of gravity of his body and filings
himself on his left side, the right wing
pointing upward and the left down
ward. How does he throw hiWSclf into
this pOSitiOnt Most writers say that it
IS by striking harder with one wing
than the other. In turning to the left
thc right wing would give a vigorous
stroke, and 50 raise the right side of
the body more than the left At 1e,t
wight it seems as if this explanation
could not be the true one. since after
Il hard stroke the right wing should
De lower than the left which has only
given gentle one, and Yet it is the
wight wing that is raised But we must
not be too haSty in drawing conclusions
from this. When tie down stroke takes
place the wings do not descend far;
the body rises 50 that the end Of the
wing appears to have described much
create" arc than it has done i'll reality
II, then, with the right wing Il much
harder stroke is given than with the
left, the right side of the body will
at once be raised. and the whole bird
will be thrown upon its left side while
The movement OF the wing itself may
not be enough to be perceptible
If birds are watched as they fly. one
wing seems always to be at the same
angle to the body rs the other 50 that
straight line connecting the tips Of the
wings would pass through the two
shoulder joints, or be parallel to a line
passing through them. Instantaneous
photographs of birds on the wing seem
10 me bear this out. one wing NAV
point up md the other down. but that
is through the sway1ng of the whole
body to one side or the other. In
spite of this there may be an inequality
Of stroke that escapes detection. and
without assuming this it seems On first
thoughts difficult to account for the
extraordinary rapid turns made. for
instance. by the swallow But. suppOS-
ING that what appears to be the case is
really so, viz, that equal force is put
into both wings. there remains another
Pc SSlbie explanation Of this movement
of the center Of gravity to the left or
right i'll turning If a bird wishes to
steer lcftWard. he may bend at the
waist toward the loft.
50 much has been said about the
riGlditY of the birds backbone that its
SUpplcnCSS at 4 point just anterior 10
the ilcum has been overlooked | find
that swallows vcrtCbral column viii
bend at this point so as to form an
angle OF 40 deg; in the case of a kcS-
tral it is 116 deg; OF Il tern. 10 deg.
of sand-martin. n uch the same as
il. the case of the swallow or in the
case Of Il duck. 1GJ deg g., a duck
can bend much less at the waist than
he other birds mentioned, and You have
only TO watch ducks on the wing to
see that they are very poor stcercrs,
iliS is but mC%gCr evidence, AMI AT
present, | have not the means of col
lccting more. Still. as far as it goes,
1t seems TO show that SrpplcnnSS of
waist goes alcn% with the power of
SWerVHG rapidly, 2Td. 4 pIiOTi. it seems
extremely improbable that such a high
~ aCTobatic feat should be performed
without calling into play every power
mat Is available. Direct observation
can. | fear, afford Ittie help. since tie
feathers Obs, urc any slight bend in
the back. But the habit that many
birds havC-it can be easily seen in
the case Of gullS-of turning their heads
liz the direction in Which they wish In
90. suggests that it may be by bending
II would be moro effective: that they
make their turns just as skate,
changes edges and flies off on an onno-
site curve by Swaying the weight of his
shoulders across to one side or the
other, Il change of balance effected NV
bend Sideways at the waist.
1t is certain that birds do not de-
pend entirely on movements of the
head or neck, since GUllS. for instance
may occasionally be seen to turn tn
the lcft while looking to the right. and
vice versa, Il point which may be made
out from Instantaneous photographs.
cannot help thinking. then. that a bird
aVailS itself Of the SupplcncSS Of its
waist to alter its balance when it wishes
to turn. Whether this is the sole
means. or whether at the same time
the wings are worked unequaIly. So
as to conducc to the same end. it is
difficult to decide. | may add that 7
have found the required muscles at
the waist considerably devcloped.-Na-
turc.