FOREST AND STREAM 
763 
The Secret of Flight in Birds 
By B. C. Tillett. 
I N spite of our great progress in the realms 
of science, the map of human knowledge 
has many barren blanks upon it still. Our 
latest notable science—aviation—is the reali¬ 
zation of many dreams, and Icarus to-day 
would use no treacherous wax to cement his 
wings. But, with all our advances, we know 
very little about the flight of birds; there is still 
much that is incomprehensible about it. “The 
way of an eagle in the air” which puzzled Solo¬ 
mon, is still a puzzle to modern men of science. 
How often have the evolutions of that volti- 
geur the sky lark excited our admiration and 
wonder as: 
“O’er fell and fountain sheen, 
O’er moor and mountain green, 
O’er the red streamer that heralds the day, 
O’er the cloudlet dim, 
O’er the rainbow rim, 
Musical cherub, soar singing away!” 
Yet how still more wonderful are the perform¬ 
ances of the larger soaring birds. How can we 
explain the easy unconcerned sailing of the gull, 
gliding abreast of a ship travelling twenty miles 
an hour? 
Now it will swing to one side, now to another, 
now visibly lifting in the air, with no apparent 
wing-beat, nor anything more than an occa¬ 
sional twist or jerk, as if in adjustment to some 
conditions at which we cannot guess. But more 
wonderful still is the spectacle at which Solo¬ 
mon was compelled to marvel: that of an eagle 
circling with apparently motionless wings, and in 
still air yet rising as it circles to immeasurable 
heights. 
The most patient and careful student of avine 
aeronautics, men who have recorded countless 
observations of the flying powers of kites, eagles, 
vultures, and other such soaring birds, are driven 
to confess that they cannot explain the phenom¬ 
ena they have so carefully and constantly stud¬ 
ied. Darwin, exact observer as he was, has very 
little to say about the flight of birds; he re¬ 
marks that “almost every year one or two land 
birds are blown across the whole Atlantic from 
North America to the western shores of Ireland 
and England.” But we are not so sure that 
they are merely blown across, for it seems more 
than probable that they exercise volition, and de¬ 
sire the long journeys they take, though wise 
enough to sail with favorable winds. 
Naturalists are pretty well agreed that birds 
—and indeed other animals—know where they 
want to go and how to get there. As Paracel¬ 
sus said, “I see my way as birds their trackless 
way.” Big aerial hosts of migrating birds pass 
over wide stretches of land and sea every spring 
and autumn; many at any rate of the smaller 
birds, at such an altitude as to be invisible to 
us. Often times flights of wild birds have been 
noticed at night time by their whistling calls 
overhead, flights of such numbers that their 
course has been observed for hundreds of miles. 
As yet, even in these days of aviation no one 
has been up to watch them in their flights for 
though it is possible that in the future aerial 
observations may be established, no ornitholo¬ 
gist claims to have hung himself up in an ob¬ 
servation cage between heaven and earth. Na¬ 
turalists have remarked upon the shiftless drift¬ 
ing movement of small eddying clouds of green 
plover, looking as if they strove to form them¬ 
selves into that consistent wedge kept so strict¬ 
ly by the wild geese. The geese are most per¬ 
fectly disciplined and drilled, so that the wedge 
seems really to give faith to that old fiction, of 
the wing of one bird, resting on that of another 
to impart solidity to the whole. There is a 
solidity, but we need not doubt that there is a per¬ 
fect freedom of individual wing-movement, too. 
Divers theories have been framed to account 
for this symmetrical figure in which these wise 
geese fly, but recondite theories are not needed. 
All show us, whether the passage of ship or 
torpedo through the sea, or of flying machine 
through the air, that the wedge is the shape for 
cleavage. If we wish to split a block of timber 
the wedge is the shape we select for the cleav¬ 
ing iron. So this the wise geese take to cleave 
the air. 
Among several theories concerning bird flight, 
perhaps the most familiar is that of “ascending 
currents,” but the experience of aeronauts has 
taught us that the wind is far more constant in 
the higher levels of the air than near the sur¬ 
face of the earth, where the varying contours 
of the land throw it into devious currents. One 
of the latest writers on the subject, Mr. E. H. 
Hankin, seems to support the doctrine of “er- 
gaen,” that is, of some property in the atmos¬ 
phere which enables a bird to take energy from 
it by means of which we have at present no 
conception. Mr. Hankin has had exceptional op¬ 
portunities of observing the flight of birds, es¬ 
pecially in India, and he finds that soaring birds 
generally avoid known ascending currents, as 
tending to upset their stability. But, after all, 
the observed phenomena in relation to the wind 
are contradictory, and birds often seem to soar 
best when the air is to our senses, motionless; 
as when the cigar smoke puffed into the air 
gives no indication of movement and when a 
feather, floating from the plumage of a soar¬ 
ing bird, continues to float, unmoved by any 
noticeable currents of air, while the bird from 
which it dropped continues without any wing 
movement to circle and rise. 
The mystery remains with us, but Mr. Han¬ 
kin believes that the “soarability” of the air de¬ 
pends in some unknown way on the sun’s action. 
He rests his case on two facts, namely: first, 
that birds do not appear to be able to soar or 
to use the atmosphere for flight in any of its 
higher forms until the sun has been up for a 
more or less definite period of time; and sec¬ 
ondly, that he thinks he has traced a constant 
relationship between sunlight in the air, or sun- 
glare, and the power of birds to soar. The time 
in the morning at which various species of birds 
begin to soar is practically constant for each 
species under like conditions, and at similar sea¬ 
sons. As a rule it seems that those birds soar 
earliest which have the least weight to lift in 
relation to the wing surface. 
It is abundantly clear that we have much to- 
learn concerning the flight of birds, and every¬ 
thing recorded about it leaves our knowledge 
incomplete with a large and ragged margin of 
suggestions, guess-work or vague generalizations. 
MULE DEER OR BLACK TAIL DEER. 
Larch Wood, Mont., Dec. 8, ’15. 
Editor Forest and Stream: 
Can you give me an opinion on the following 
question: A says there is no difference between 
the so-called mule deer and black tail deer of 
the Badland and Rocky Mountain region. B 
says they are different deer. 
Please set us right, and oblige a subscriber. 
D. W. B. 
[A is right. The so-called mule deer and so- 
called black tail deer of the Badlands and the 
Rocky Mountain region are the same species. 
Black tail is the vernacular name, referring, of 
course, to the black paint brush tip of the deer’s 
tail. Mule deer is the book name, given from the 
long ears. There is, however, another deer in 
the northwest coast region called black tail deer, 
but it is never seen in the Rocky Mountains or 
in the Badlands of the plains. It is quite differ¬ 
ent from the mule deer, especially in the char¬ 
acter of the tail and of the ears. Any good na¬ 
tural history will set you right on this point.— Ed.] 
• 
WILSON ORNITHOLOGICAL CLUB. 
Notice has been sent out by T. L. Hankinson, 
secretary, that the Wilson Ornithological Club 
would hold a meeting December 28 and 29 
just past at the Ohio Archaeological Society, 
State University, Columbus, Ohio, with the 
American Association for the Advancement of 
Science. 
A business meeting for December 28 at 4 
P. M. and one in the evening, at 8 P. M., were 
announced. 
The Wilson Ornithological Club is known to 
all ornithologists for much excellent work, and 
especially for its publication of The Wilson Bul¬ 
letin, in which much interesting bird news ap¬ 
pears. Dr. Lynds Jones, of the Spear Labora¬ 
tory, Oberlin, Ohio, is the editor of the Bulletin. 
