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R Bonser

Publications and source records attributed to R Bonser.

6 recordsLinked to original sources
PubMed1996

Measuring leg thrust forces in the common starling

We describe the design of a force-transducing perch which measures the reaction forces of small birds taking off and landing. In common starlings, landing forces are lower than take-off forces, because the bird may decelerate prior to landing by using its wings. Both landing and take-off forces are significantly correlated with body mass; however, the angles of these reaction forces show no significant mass-dependence and are not repeatable within individuals. Diversity in take-off or landing strategy could be advantageous in confusing predators.

Journal Article↗
PubMed1995

The Young's modulus of feather keratin

The flexural stiffness of the rachis varies along the length of a primary feather, between primaries and between species; the possible contribution of variations in the longitudinal Young's modulus of feather keratin to this was assessed. Tensile tests on compact keratin from eight species of birds belonging to different orders showed similar moduli (mean E=2.50 GPa) in all species apart from the grey heron (E=1.78 GPa). No significant differences were seen in the modulus of keratin from primaries 7­10 in any species. There was a systematic increase in the modulus distally along the length of the rachis from swan primary feathers. Dynamic bending tests on swan primary feather rachises also showed that the longitudinal elastic modulus increases with increasing frequency of bending over the range 0.1­10 Hz and decreases monotonically with increasing temperature over the range -50 to +50 °C. The position-, frequency- and temperature-dependent variations in the modulus are, however, relatively small. It is concluded that, in the species studied, the flexural stiffness of the whole rachis is principally controlled by its cross-sectional morphology rather than by the material properties of the keratin.

Journal Article↗