THE 
GAIT AND FLIGHT 
OF BIRDS. 
By 
FRANK FINN, 
B.A., F.Z.S. 
Fig. 1. Ostrich’s Foot. 
Eee as a general rule birds employ but one pair of limbs at a time in 
executing the movements necessary for progression, there is a considerable amount 
of variety in their actions, which are often much misrepresented even by scientific 
writers. 
When moving on the ground, birds have in the ordinary way but two modes of 
progression—walking, when each foot is advanced alternately, and hopping, when both 
are moved together in a series of leaps. By increasing the rapidity of the alternate 
movements the walk is converted into a run, which is often very rapid. As a general 
rule, birds are digitigrade—that is to say, they walk on the toes only, the whole 
surface of at least the three anterior toes being applied to the ground. But 
there are a few exceptions. The Ostrich carries the digitigrade mode of progression 
to a greater length than any other bird, the basal joints of its two toes beg raised 
off the ground, so that the foot has a pastern like that of an ordinary ungulate 
mammal. To this, no doubt, the peculiar springy gait of this great bird is due (see 
Fig. 1). On the other hand, some birds in which the shank (wrongly called in 
ornithology the tarsus) 1s peculiarly short : 
apply this also to the ground in walking, <I 
and are thus plantigrade, simce the shank ie 
of the bird corresponds to the planta or 
sole of a mammal. This is the case with 
some of the very short-legged parrots, such 
as the Salmon-Crested Cockatoo (Cacatua 
moluccensis), with the typical Swifts (Cyp- 
selus), and the Mouse-Birds (Coliide), all of 
them being birds which naturally walk very 
little. It has been stated on high scientific 
authority that several groups of diving 
birds, Penguins, Auks, etc., are plantigrade, 
but this is a mistake; they walk on their 
toes like other birds, although they may, 
_ like many of these, sometimes apply the 
whole of the shank to the ground when 
sitting. The Guillemot always does this 
(Fig. 3), but it certainly can walk on its 
toes at times. 
Ly 
The Divers (Colymbide) appear to be | 
unable to walk at all, but to shove them- 
selves along on thew breasts like seals, = Zi 
although there is at least one instance Fig. 2, Crane walking. 
317 
