Through this mirrory darkness he staggered home: Mark Standfuss, a salesclerk, a demigod, fair-haired Mark, a lucky fellow with a high starched collar. At the back of his neck, above the white line of that collar, his hair ended in a funny, boyish little tag that had escaped the barber's scissors. That little tag was what made Klara fall in love with him, and she swore that it was true love, that she had quite forgotten the handsome ruined foreigner who last year had rented a room from her mother, Frau Heise.
(Details of a Sunset)

I pondered the name of the hero for a while and I guess I've got it: Mark is a bird, namely a heron (tsaplya, Reiher). Herons can often be seen standing on one foot (hence Standfuss, "Mr Standfoot") in the middle of a bog or a rice field. The egrets (white herons) have aigrettes (back plumes) as a head ornament.

All other characters in the story seem to be birds too. Frau Heise (no relation of Charlotte Haze, or is she?) is probably a goose. Mark's friend Adolf who stands, "propping himself on his cane as if it were a tail," makes one think of a woodpecker.

Note the man at the corner, in apron and peaked cap, selling frankfurters, crying out in a tender and sad birdlike whistle: "Würstchen, würstchen..."

Btw., Sirin (rara avis indeed!) is also a bird and a demigod. Frau Heise's former lodger for whom Klara leaves Mark (who never learns of it) is a handsome ruined foreigner...