Graphics Reference
In-Depth Information
Members of the crow family, such as magpies, rooks, and jays, get around
on the ground by walking, though they will often hop in both a symmetrical
and asymmetrical fashion when faster speeds are called for. During an
asymmetrical hop it can be clearly seen that the feet are out of phase with
each other but by less than half a stride. The slow walk of a large bird with
short legs results in a noticeable sideways motion coupled with a sharp
forward and backward movement of the head. Larger birds with long legs
tend not to demonstrate this level of waddle. This waddling action is much
more pronounced if the legs are located toward the rear of the body, as in
ducks, geese, and swans.
FIG 4.65
Larger birds often mix
modes of locomotion between
walking and hopping.
Flightless birds have to take other action if they are to avoid predation. Larger
birds run in a more upright fashion than the smaller passerines. Emus, rheas,
and ostriches all have long, powerful legs and rounded bodies with small
heads on the end of long, slender necks. For the most part these birds walk
upright; when need arises they run with long, powerful strides. The reduction
of the number of toes to two on the foot of the ostrich enables it to generate
increased thrust during the duty phase of the stride.
Fish
Fish might not be as advanced as either birds or mammals in that they do not
display the same levels of intelligence, highly developed social bonding, or
complex patterns of behavior, but they do form a unique part of the animal
kingdom, occupying the largest part of our planet—water. They are uniquely
adapted for life across a broad range of environments.
