36 THE te OF BIRDS 
a skilled and experienced pilot, he is, apparently, 
as steady as he rushes down towards the earth as 
a bird could be. But,if he did lose his balance, it 
would be fatal, whereas to the bird a momentary 
loss of equilibrium is of no consequence. 
Leaving aviators and their splendid achievements, 
I must describe another attitude sometimes adopted 
by a bird in gliding downward. He will extend his 
wings to the full, but hold them slanting upward 
(see Pl. 111). Obviously in this position the wings 
give less support, and so he descends. But he 
descends slowly, not with the rush that is character- 
istic of the head-foremost downward glide. The 
wings do not travel edgeways through the air and 
so they check his pace. Their upward slant is, as 
I have before remarked, advantageous to balance. 
I must now conclude this brief investigation of 
the bird’s stability when on the wing. What we 
see in the flight of birds—I am not now speaking 
of soaring—is not a steady, careful maintenance 
of equilibrium, but an instantaneous recovery of 
balance whenever it is lost. The bird can afford 
to be indifferent to the difficult problems which 
this subject presents. He has something much 
better than the power of maintaining equilibrium. 
However the gusts and vagaries of the wind may 
upset him, he can right himself at once. He owes 
his wonderful stability to some extent to his fine 
build and the elasticity of his feathers, but mainly 
to manoeuvres and adjustments that cannot be 
mere reflexes. The flying machine which he pilots 
is admirably built ; still it can never dispense with 
a pilot. But his voluntary adjustments are largely 
