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Hovering Performance of Hummingbirds in Hyperoxic Gas Mixtures

Douglas L. Altshuler*, Peng Chai and Jeff S. P. Chen

Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA



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  		Fig. 1. Estimated body mass-specific power output (Wkg-1) assuming perfect elastic energy storage (Pper) versus the measured hover-feeding duration of ruby-throated hummingbirds (means ±1 S.E.M., N=6) hovering in either hyperoxic (filled squares) or normoxic (open squares) heliox. Data are from the hummingbirds used in the aerodynamic failure experiment.

 


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  		Fig. 2. Hover-feeding duration (A) and rates of oxygen consumption (VO2) (B) across decreasing densities as normal air was gradually replaced with either hyperoxic (filled squares) or normoxic (open squares) heliox. Values are means ±1 S.E.M. (N=6) from individual birds at each air density level. %O2 is the oxygen concentration at each density under hyperoxia. Data are from the hummingbirds used in the density experiment.

 


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  		Fig. 3. Estimated body mass-specific mechanical muscle power output (Wkg-1) assuming perfect elastic energy storage (Pper) during hyperoxic (filled squares) and normoxic (open squares) heliox replacement of normal air. Values are means ±1 S.E.M. (N=6) from individual birds at each air density level. %O2 is the oxygen concentration at each density under hyperoxia. Data are from the hummingbirds used in the density experiment.

 


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  		Fig. 4. Hover-feeding duration (means ±1 S.E.M., N=7) of ruby-throated hummingbirds across decreasing air densities as normal air was gradually replaced with either hyperoxic (filled squares) or normoxic (open squares) heliox. Values are means ±1 S.E.M. from individual birds at each density level. %O2 is the oxygen concentration at each density under hyperoxia. Data are from the hummingbirds used in the choice experiment.

 


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  		Fig. 5. Discrimination between feeders with hyperoxia-filled (filled squares) or normoxia-filled (open squares) corollas during failure and the two feeding bouts just prior to failure of hovering. Values are the mean incidence ±1 S.E.M. of choice for hummingbirds at that density (N=7). Birds that sampled both feeders during one feeding bout received a score of 1 for both feeders. Data are from the hummingbirds used in the choice experiment.

 

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© The Company of Biologists Ltd 2001