Nostrils naked, not covered feathers (ris.1.1). Tsevka naked, but if the opera, there is no more than a quarter length in males at the rear of the bobbin acute rogovaya spur or papilla. The edges of the fingers always without fringe of the outgrowths of horns.

Nostrils covered feathers (Figure 1.2). Tsevka opera, not less than half the length and frequency opera to the most fingers. At the edges of the fingers are (especially in winter) fringe horn of the outgrowths.