BIRD ADAPTATIONS 



100 



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o 

 o 

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I- 

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TEMPERATURE 



Figure 10. Overlap of insulative (dashed line) and metabolic (solid line) 

 adjustments for thermoregulation in small wild birds. After insulation reaches 

 its maximum, increases in metabolism carry the bird to its lower limit of tolerance 

 (Lj). This slope extrapolates to body temperature (BT) according to Newton's 

 law of cooling. Above body temperature, metabolism increases, and insulation 

 reaches its minimum as the upper limit of tolerance is reached (L ). 



307 



