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RE: Resurrection of the New Papers - correction
Citation for Tobalske and Dial (2007) is Journal of Experimental Biology
Tobalske, B.W. and Dial. K.P. (2007). Aerodynamics of wing-assisted
incline running in birds.
Summary: "Wing-assisted incline running (WAIR) is a form of locomotion in
which a bird flaps its wings to aid its hindlimbs in climbing a slope.
WAIR is used for escape in ground birds, and the ontogeny of this behavior
in precocial birds has been suggested to represent a model analogous to
transitional adaptive states during the evolution of powered avian flight.
To begin to reveal the aerodynamics of flap-running, we used digital
particle image velocimetry (DPIV) and measured air velocity, vorticity,
circulation and added mass in the wake of chukar partridge _Alectoris
chukar_ as they engaged in WAIR (incline 65?85°; N=7 birds) and ascending
flight (85°, N=2). To estimate lift and impulse, we coupled our DPIV data
with three-dimensional wing kinematics from a companion study. The
ontogeny of lift production was evaluated using three age classes: baby
birds incapable of flight [6?8 days post hatching (d.p.h.)] and volant
juveniles (25?28 days) and adults (45+ days). All three age classes of
birds, including baby birds with partially emerged, symmetrical wing
feathers, generated circulation with their wings and exhibited a wake
structure that consisted of discrete vortex rings shed once per downstroke.
Impulse of the vortex rings during WAIR was directed 45±5° relative to
horizontal and 21±4° relative to the substrate. Absolute values of
circulation in vortex cores and induced velocity increased with increasing
age. Normalized circulation was similar among all ages in WAIR but 67%
greater in adults during flight compared with flap-running. Estimated lift
during WAIR was 6.6% of body weight in babies and between 63 and 86% of
body weight in juveniles and adults. During flight, average lift was 110%
of body weight. Our results reveal for the first time that lift from the
wings, rather than wing inertia or profile drag, is primarily responsible
for accelerating the body toward the substrate during WAIR, and that
partially developed wings, not yet capable of flight, can produce useful
lift during WAIR. We predict that neuromuscular control or power output,
rather than external wing morphology, constrain the onset of flight ability
during development in birds."
Rubenson, J., Lloyd, D.G., Besier, T.F., Heliams, D.B., and Fournier, P.A.
(2007). Running in ostriches (_Struthio camelus_): three-dimensional joint
axes alignment and joint kinematics. Journal of Experimental Biology 210:
Summary: "Although locomotor kinematics in walking and running birds have
been examined in studies exploring many biological aspects of bipedalism,
these studies have been largely limited to two-dimensional analyses.
Incorporating a five-segment, 17 degree-of-freedom (d.f.) kinematic model
of the ostrich hind limb developed from anatomical specimens, we quantified
the three-dimensional (3-D) joint axis alignment and joint kinematics
during running (at ~3.3 m s?1) in the largest avian biped, the ostrich.
Our analysis revealed that the majority of the segment motion during
running in the ostrich occurs in flexion/extension. Importantly, however,
the alignment of the average flexion/extension helical axes of the knee and
ankle are rotated externally to the direction of travel (37° and 21°,
respectively) so that pure flexion and extension at the knee will act to
adduct and adbuct the tibiotarsus relative to the plane of movement, and
pure flexion and extension at the ankle will act to abduct and adduct the
tarsometatarsus relative to the plane of movement. This feature of the
limb anatomy appears to provide the major lateral (non-sagittal)
displacement of the lower limb necessary for steering the swinging limb
clear of the stance limb and replaces what would otherwise require greater
adduction/abduction and/or internal/external rotation, allowing for less
complex joints, musculoskeletal geometry and neuromuscular control.
Significant rotation about the joints' non-flexion/extension axes
nevertheless occurs over the running stride. In particular, hip abduction
and knee internal/external and varus/valgus motion may further facilitate
limb clearance during the swing phase, and substantial
non-flexion/extension movement at the knee is also observed during stance.
Measurement of 3-D segment and joint motion in birds will be aided by the
use of functionally determined axes of rotation rather than assumed axes,
proving important when interpreting the biomechanics and motor control of
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