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Table 4.

Sensitivity analysis for the daily energy requirements of little auks and Brünnich's guillemots wintering off southwest Greenland

Brünnich's guillemots
Little auks
ParametersMin. valueMax. valueRangeVariation of seasonal energy requirements (%)Min. valueMax. valueRangeVariation of seasonal energy requirements (%)
Endotherm         
   Plumage depth: dorsal, ventral (mm) 5.0, 14.4 6.2, 17.6 ±10% ±7.16 6.7, 11.5 8.1, 14.1 ±10% ±5.34 
   Plumage reflectivity: dorsal, ventral (%) 0.34, 0.67 0.42, 0.82 ±10% <±0.01 0.36, 0.58 0.44, 0.71 ±10% ±0.02 
   Feather length: dorsal, ventral (mm) 29.2, 22.5 35.6, 27.5 ±10% ±0.21 18.0, 17.3 22.0, 21.1 ±10% ±1.45 
   Feather diameter (μm) 29.7 36.3 ±10% ±2.18 29.7 36.3 ±10% ±0.48 
   Plumage density (1 cm–24114.8 5029.2 ±10% ±0.66 4114.8 5029.2 ±10% ±0.89 
   Body core temperature (°C) 39.6 40.3 Min.–max. ±1.83 36.1 40.1 ±10% ±2.02 
   Digestive efficiency (%) 0.63 0.77 ±10% <±0.01 0.72 0.88 ±10% ±0 
   Exhaled air temperature–local air temperature (°C) 1.8 2.2 ±10% 0.01 1.8 2.2 ±10% 0.01 
   Flight metabolism (W) 79.2 96.8 ±10% ±0.84 9.513 11.627 ±10% ±0.31 
   Ventral area contacting substrate (%) 0.225 0.275 ±10% ±0.06 0.225 0.275 ±10% ±0.17 
   Flight speed (m s–116.25 19.87 ±10% ±0.23 11.7 14.3 ±10% ±0.28 
   Dive depth (m) 43.3 52.8 ±10% <±0.01 24.57 30.03 ±10% <±0.01 
   Flight altitude (m) 4.5 5.5 ±10% <±0.01 4.5 5.5 ±10% <±0.01 
Climate         
   Air temperature (°C) –7.80 5.17 Min.–max. ±8.52 –7.80 5.17 Min.–max. ±8.87 
   Sea surface temperature (°C) –0.60 5.27 Min.–max. ±0.04 –0.60 5.27 Min.–max. ±0.03 
   Relative humidity (%) 55.0 97.2 Min.–max. ±1.20 55.0 97.2 Min.–max. ±1.44 
   Wind speed (m s–12.0 17.5 Min.–max. ±2.57 2.0 17.5 Min.–max. ±2.70 
   Cloud cover (%) 100 Min.–max. <±0.01 100 Min.–max. <±0.01 
Brünnich's guillemots
Little auks
ParametersMin. valueMax. valueRangeVariation of seasonal energy requirements (%)Min. valueMax. valueRangeVariation of seasonal energy requirements (%)
Endotherm         
   Plumage depth: dorsal, ventral (mm) 5.0, 14.4 6.2, 17.6 ±10% ±7.16 6.7, 11.5 8.1, 14.1 ±10% ±5.34 
   Plumage reflectivity: dorsal, ventral (%) 0.34, 0.67 0.42, 0.82 ±10% <±0.01 0.36, 0.58 0.44, 0.71 ±10% ±0.02 
   Feather length: dorsal, ventral (mm) 29.2, 22.5 35.6, 27.5 ±10% ±0.21 18.0, 17.3 22.0, 21.1 ±10% ±1.45 
   Feather diameter (μm) 29.7 36.3 ±10% ±2.18 29.7 36.3 ±10% ±0.48 
   Plumage density (1 cm–24114.8 5029.2 ±10% ±0.66 4114.8 5029.2 ±10% ±0.89 
   Body core temperature (°C) 39.6 40.3 Min.–max. ±1.83 36.1 40.1 ±10% ±2.02 
   Digestive efficiency (%) 0.63 0.77 ±10% <±0.01 0.72 0.88 ±10% ±0 
   Exhaled air temperature–local air temperature (°C) 1.8 2.2 ±10% 0.01 1.8 2.2 ±10% 0.01 
   Flight metabolism (W) 79.2 96.8 ±10% ±0.84 9.513 11.627 ±10% ±0.31 
   Ventral area contacting substrate (%) 0.225 0.275 ±10% ±0.06 0.225 0.275 ±10% ±0.17 
   Flight speed (m s–116.25 19.87 ±10% ±0.23 11.7 14.3 ±10% ±0.28 
   Dive depth (m) 43.3 52.8 ±10% <±0.01 24.57 30.03 ±10% <±0.01 
   Flight altitude (m) 4.5 5.5 ±10% <±0.01 4.5 5.5 ±10% <±0.01 
Climate         
   Air temperature (°C) –7.80 5.17 Min.–max. ±8.52 –7.80 5.17 Min.–max. ±8.87 
   Sea surface temperature (°C) –0.60 5.27 Min.–max. ±0.04 –0.60 5.27 Min.–max. ±0.03 
   Relative humidity (%) 55.0 97.2 Min.–max. ±1.20 55.0 97.2 Min.–max. ±1.44 
   Wind speed (m s–12.0 17.5 Min.–max. ±2.57 2.0 17.5 Min.–max. ±2.70 
   Cloud cover (%) 100 Min.–max. <±0.01 100 Min.–max. <±0.01 

Minimum and maximum input values from Micro2006c and Endo2007d are the minimum and maximum values recorded for each parameter or ±10% of the average. As body mass is highly correlated with field metabolic rate (FMR) in most animals (Ellis and Gabrielsen,2002), a strong variation in energy requirements is expected when body mass varies, independently of the model. Therefore, this parameter does not appear in the sensitivity analysis. The maximum variation of calculated energy requirements is marked in bold. It highlights the fact that air temperature is the critical parameter affecting the energy balance of wintering alcids. However, it is also important to note that plumage depth is the second most important parameter

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