The Retopology Piero now has his legs attached:
And the legs in detail:
My solution for the bottom of the nostrils (view to the beak's front):
The triangle to the right of the right nostril's bottom wil only be visible under extreme angles:
The nostrils rims shrunken a little bit giving them nice surrounding lips:
Finishing the mouth cavity by smoothing edge loops with the help of "Relax" from "Loop Tools"
Piero's retopologized base mesh is now finished and ready for adding the main feathers which will be modeled in the next step: