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Fig. 4. The position of the digitized points representing the body of the great
cormorant, relative to the mean swimming direction. (A) The center of mass of
the bird demonstrated no significant deviations from the swimming direction in
the Z direction (right/left). (B) Deviations in the Y
direction (up/down) of three points on the body. Positive values are upward
movements, and negative values are downward movements. The points are at
anterior (base of neck), center (center of mass) and posterior (base of tail)
locations on the body unit (points 2, 8 and 6 in
Fig. 1C). All points descended
during the stroke phase and ascended during the glide and recovery phases. The
base of the neck (most anterior point) follows the pattern of the center of
mass, indicating that the entire body is descending and ascending. The larger
amplitude of the base of the tail can be attributed to the tilt of the body
(rotation). The deviations are relative to the mean direction of the birds,
calculated as the straight line connecting the position of point 3 in
Fig. 1C (for the XY
plane) or point 11 in Fig. 1B
(for the XZ plane) at the beginning and end of the paddling cycle.
The red broken arrows mark these directions. Each data point is the mean
± S.E.M. of all birds (N=9).
The X axis is the same as described in
Fig. 2.
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