Figure 8.

Feather area per unit skin surface $(\mathrm{pl})$ as a function of $(\mathrm{feather}\hspace{0.17em}\mathrm{length}\hspace{0.17em}(\mathrm{mm})\times \mathrm{feather}\hspace{0.17em}\mathrm{width}\hspace{0.17em}(\mathrm{mm})\times \mathrm{number}\hspace{0.17em}\mathrm{of}\hspace{0.17em}\mathrm{feathers})/(25\hspace{0.17em}{\mathrm{mm}}^2)$ per body part. We plotted the median as the line that divides the box and the upper and lower quartiles as the end of the boxes. The extreme lines each show the highest and the lowest value.