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On vision in birds: coordination of head-bobbing and gait stabilises vertical head position in quail.

Nyakatura JA, Andrada E - Front. Zool. (2014)

Bottom Line: We were interested in the biomechanics behind this phenomenon.Significant differences in the timing of head-bobbing were found between gaits.The timing of the head-bobbing behaviour naturally favoured by quail benefits vision during vaulting and bouncing gaits and potentially helps reducing the mechanical cost associated with head bobbing when using a bouncing gait.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität, Erbertstraße 1, 07743 Jena, Germany. john.nyakatura@uni-jena.de.

ABSTRACT

Introduction: Head-bobbing in birds is a conspicuous behaviour related to vision comprising a hold phase and a thrust phase. The timing of these phases has been shown in many birds, including quail, to be coordinated with footfall during locomotion. We were interested in the biomechanics behind this phenomenon. During terrestrial locomotion in birds, the trunk is subjected to gait-specific vertical oscillations. Without compensation, these vertical oscillations conflict with the demands of vision (i.e., a vertically stable head position). We tested the hypothesis that the coordination between head-bobbing and trunk movement is a means of reconciling the conflicting demands of vision and locomotion which should thus vary according to gait.

Results: Significant differences in the timing of head-bobbing were found between gaits. The thrust phase was initiated just prior to the double support phase in walking (vaulting) trials, whereas in running (bouncing) trials, thrust started around midstance. Altering the timing of head-trunk-coordination in simulations showed that the timing naturally favoured by birds minimizes the vertical displacement of the head. When using a bouncing gait the timing of head bobbing had a compensatory effect on the fluctuation of the potential energy of the bird's centre of mass.

Conclusion: The results are consistent with expectations based on the vertical trunk fluctuations observed in biomechanical models of vaulting and bouncing locomotion. The timing of the head-bobbing behaviour naturally favoured by quail benefits vision during vaulting and bouncing gaits and potentially helps reducing the mechanical cost associated with head bobbing when using a bouncing gait.

No MeSH data available.


Related in: MedlinePlus

Characteristics of the experimental data. A: Onset of the double support phase and the thrust phase as a percentage of the time span between subsequent hindlimb midstance events. B: % Congruity was used to differentiate between trials with vaulting mechanics (< 50% congruity) and trials with bouncing mechanics (> 50% congruity). Boxes represent range between first and third quartiles (i.e.. 50% of the data), the line within the box represents the median and the length of each whisker corresponds to the lowest datum within 1.5 IQR (interquartile range) of the lower and 1.5 IQR of the upper quartile, respectively; outliers (more than 1.5 IQR) depicted as open circles; **: significant at the p = 0.01 level; ***: significant at p = 0.001 level; d: Cohen’s d (effect size).
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Figure 3: Characteristics of the experimental data. A: Onset of the double support phase and the thrust phase as a percentage of the time span between subsequent hindlimb midstance events. B: % Congruity was used to differentiate between trials with vaulting mechanics (< 50% congruity) and trials with bouncing mechanics (> 50% congruity). Boxes represent range between first and third quartiles (i.e.. 50% of the data), the line within the box represents the median and the length of each whisker corresponds to the lowest datum within 1.5 IQR (interquartile range) of the lower and 1.5 IQR of the upper quartile, respectively; outliers (more than 1.5 IQR) depicted as open circles; **: significant at the p = 0.01 level; ***: significant at p = 0.001 level; d: Cohen’s d (effect size).

Mentions: The timing of thrust differed significantly between trials with vaulting mechanics (vaulting trials) and trials with bouncing mechanics (bouncing trials) (Figure 3). In vaulting trials, the onset of thrust largely overlapped with the onset of the double support phase. In bouncing trials, the onset of thrust occurred around midstance. The timing of head-bobbing (experimental data) resulted in significantly smaller vertical head displacements and thus a straighter trajectory for the head than in trials in which the timing of head-body-coordination was inversed (simulation data).


On vision in birds: coordination of head-bobbing and gait stabilises vertical head position in quail.

Nyakatura JA, Andrada E - Front. Zool. (2014)

Characteristics of the experimental data. A: Onset of the double support phase and the thrust phase as a percentage of the time span between subsequent hindlimb midstance events. B: % Congruity was used to differentiate between trials with vaulting mechanics (< 50% congruity) and trials with bouncing mechanics (> 50% congruity). Boxes represent range between first and third quartiles (i.e.. 50% of the data), the line within the box represents the median and the length of each whisker corresponds to the lowest datum within 1.5 IQR (interquartile range) of the lower and 1.5 IQR of the upper quartile, respectively; outliers (more than 1.5 IQR) depicted as open circles; **: significant at the p = 0.01 level; ***: significant at p = 0.001 level; d: Cohen’s d (effect size).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3987125&req=5

Figure 3: Characteristics of the experimental data. A: Onset of the double support phase and the thrust phase as a percentage of the time span between subsequent hindlimb midstance events. B: % Congruity was used to differentiate between trials with vaulting mechanics (< 50% congruity) and trials with bouncing mechanics (> 50% congruity). Boxes represent range between first and third quartiles (i.e.. 50% of the data), the line within the box represents the median and the length of each whisker corresponds to the lowest datum within 1.5 IQR (interquartile range) of the lower and 1.5 IQR of the upper quartile, respectively; outliers (more than 1.5 IQR) depicted as open circles; **: significant at the p = 0.01 level; ***: significant at p = 0.001 level; d: Cohen’s d (effect size).
Mentions: The timing of thrust differed significantly between trials with vaulting mechanics (vaulting trials) and trials with bouncing mechanics (bouncing trials) (Figure 3). In vaulting trials, the onset of thrust largely overlapped with the onset of the double support phase. In bouncing trials, the onset of thrust occurred around midstance. The timing of head-bobbing (experimental data) resulted in significantly smaller vertical head displacements and thus a straighter trajectory for the head than in trials in which the timing of head-body-coordination was inversed (simulation data).

Bottom Line: We were interested in the biomechanics behind this phenomenon.Significant differences in the timing of head-bobbing were found between gaits.The timing of the head-bobbing behaviour naturally favoured by quail benefits vision during vaulting and bouncing gaits and potentially helps reducing the mechanical cost associated with head bobbing when using a bouncing gait.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität, Erbertstraße 1, 07743 Jena, Germany. john.nyakatura@uni-jena.de.

ABSTRACT

Introduction: Head-bobbing in birds is a conspicuous behaviour related to vision comprising a hold phase and a thrust phase. The timing of these phases has been shown in many birds, including quail, to be coordinated with footfall during locomotion. We were interested in the biomechanics behind this phenomenon. During terrestrial locomotion in birds, the trunk is subjected to gait-specific vertical oscillations. Without compensation, these vertical oscillations conflict with the demands of vision (i.e., a vertically stable head position). We tested the hypothesis that the coordination between head-bobbing and trunk movement is a means of reconciling the conflicting demands of vision and locomotion which should thus vary according to gait.

Results: Significant differences in the timing of head-bobbing were found between gaits. The thrust phase was initiated just prior to the double support phase in walking (vaulting) trials, whereas in running (bouncing) trials, thrust started around midstance. Altering the timing of head-trunk-coordination in simulations showed that the timing naturally favoured by birds minimizes the vertical displacement of the head. When using a bouncing gait the timing of head bobbing had a compensatory effect on the fluctuation of the potential energy of the bird's centre of mass.

Conclusion: The results are consistent with expectations based on the vertical trunk fluctuations observed in biomechanical models of vaulting and bouncing locomotion. The timing of the head-bobbing behaviour naturally favoured by quail benefits vision during vaulting and bouncing gaits and potentially helps reducing the mechanical cost associated with head bobbing when using a bouncing gait.

No MeSH data available.


Related in: MedlinePlus