Environmental Engineering Reference
In-Depth Information
4.7 Engraving of a galloping horse based on Muybridge's
(1887) classic photographs of animal locomotion. (b) Energy
costs of different horse gaits (Carrier 1984).
But bustards rarely fly, and other large flyers, be it con-
dors (8-10 kg) or albatrosses (7-9 kg), spend hours as
gliders aided by wind currents rather than as active flap-
pers. Satellite monitoring of magnificent frigate birds, the
only species besides swifts to spend nights on the wing,
shows them soaring in thermals up to 2.5 km and
descending to the sea surface only once every 8 h or so
(Weimerskirch et al. 2003). Some large birds save energy
by using other birds' airstreams in V formations: mea-
sured values in great white pelicans show they save 11%-
14% by extending their gliding time in a vortex wake
(Weimerskirch, Martin et al. 2001).
Typical flight speeds are proportional to a wing load-
ing to power ratio of 0.55, and hence to M
0
:
18
. Speeds
minimizing the cost of transport (in m/s) are equal to
14.6M
0
:
2
, resulting in usual velocities of about 9 m/s
for starlings, 14 m/s for ducks, and close to 20 m/s
for
succession of tidal flows, a complex arrangement of
parabronchi and air sacs allows birds to use unidirectional
flow through a large number of parallel tubes. Avian para-
bronchi remove almost 30% more oxygen than mamma-
lian alveoli. Vertebrate runners become comatose at high
altitudes, but even small songbirds fly for 10
3
km at alti-
tudes of 3-6 km, and bar-headed geese were seen above
Mount Everest. The energetics of long-distance migra-
tions is explained by preflight accumulation of fat and by
reliance on tailwinds. Lipid/lean dry weight ratio is
0.34-0.44 in sparrows, up to 3.42 in blackpoll warblers,
and as high as 3.5 for ruby-throated hummingbirds ready
to migrate (Blem 1980). In-flight use of 25% M is com-
mon; 50% loss appears to be the maximum.
Terrestrial gaits begin with walk and then speed up
to running modes of trotting and galloping (fig. 4.7).
Gaits are distinguished by their footfall patterns, duty
factors (fractions of a cycle for which a given foot is
large geese. Whereas mammalian breathing is a
