Stora Karlsö is the biggest bird mountain in the Baltic and truly worth visiting, not only by avid bird watchers; the average tourist will also be fascinated by the bird life on the island. At the end of June or the beginning of July a spectacular drama is played out on the island when the newborn guillemot chicks jump from the high cliff ledges down to the sea responding to the call of their parents.
The auks – penguins of the North
Three kinds of auks dominate the bird life on Stora Karlsö: common guillemot (Uria aalge), razorbill (Alca torda) and black guillemot (Cepphus grille). Best known are the guillemots and more than 6,500 pairs breed and hatch on the island, but actually there are even more razorbills, about 7,500 pairs. The number of black guillemot has been declining since the 1960s and today only about half a dozen pairs breed on the island.
The common guillemot has a simple pointed black bill and a brownish-black back, which distinguishes this species from the razorbill with its broad bill, supposed to resemble old-fashioned razors. These auks nest on narrow ledges, small caves and cliffs, accessible only from the face of the steep western side, which makes Stora Karlsö an ideal site.
Other birds of interest are various species of wild duck (Anatidae), gulls, tern, among others and small song birds can be seen and heard in the bushes and shrubbery.