| dc.description.abstract | The adaptations of the wing and muscles of flight in several species of birds
exhibiting differing flight patterns have been investigated. Sixty two specimen of
birds belonging to seventeen species were used. They represented non-flying and
flapping fliers.
Wing span, aspect ratio, wing loading, wing surface area, body mass and
flight muscle mass. were determined. The flight muscles (pectoralis and
supracoracoideus)were examined. Muscles on one side of the bird were frozen in
liquid nitrogen cooled isopentane and sectioned for histochemistry. The muscles on
the other side were fixed in situ through perfusion with buffered 3% glutaraldehyde
solution for light microscopy.
The histochemical sections were analyzed qualitatively for fibre types and
then morphometric ally by point counting method to estimate the volume densities
of different types of fibres and capillary densities in various regions of each muscle.
The small passerine birds possessed only fast oxidative glycolytic (FOG)
fibres in the pectoralis muscle while all the large birds had FOG and fast glycolytic
(FG) fibres. In the Domestic Fowl, slow oxidative (SO) fibres were located in a
circumscribed region in the caudal part of the proximal one third of the muscle. The
supracoracoideus muscle contained only FOG and FG fibres in all species of birds
studied. The volume density of FOG fibres increased from the superficial to the deep
regions of muscles while FG fibres decreased in the same direction. There were,
however, no regional differences in volume densities of individual fibre types along
the proximal to distal direction.
There was a strong correlation between body mass and flight muscle mass
(R2=0.961) and also with wing surface area (R2 =0.926). Non- fliers had higher
wing loading than flappers. Aspect ratio did not differ between non-flying and
flappers but those birds with intermittent gliding capability had a higher aspect ratio.
Fast oxidative glycolytic fibres had a significantly (p < 0.01) higher capillary
count per area than FG fibres but individual FG fibres had higher capillaries per
fibre than FOG fibres.
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Flapping fliers showed greater adaptations to flight than non-fliers. The high
volume density of FOG fibres and capillary counts per area in FG and FOG fibres
may enable the agile fliers to meet the extremely high demands of energy required
for sustained flight. | en |
