The stamp pictures the Atlantic puffin (Fratercula arctica).
(http://en.wikipedia.org/wiki/Atlantic_Puffin)
(http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3321)
Benedikt also included a nice surprise in his envelope: the WWF stamp serie from Iceland (Gyrfalcon), issued in 1992, in very nice used condition. Thank you very much for this, Benedikt!