The Collaborative International Dictionary of English v.0.48:

Ousel \Ou"sel\ ([oo^]"z'l), n. [OE. osel, AS. [=o]sle; akin to
   G. amsel, OHG. amsala, and perh. to L. merula blackbird. Cf.
   Merle, Amsel.] (Zool.)
   One of several species of European thrushes, especially the
   blackbird (Merula merula, or Turdus merula), and the
   mountain or ring ousel (Turdus torquatus). [Written also
   ouzel.]
   [1913 Webster]

   Rock ousel (Zool.), the ring ousel.

   Water ousel (Zool.), the European dipper (Cinclus
      aquaticus), and the American dipper (Cinclus
      Mexicanus).
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Blackbird \Black"bird\ (bl[a^]k"b[~e]rd), n. (Zool.)
   In England, a species of thrush (Turdus merula), a singing
   bird with a fin note; the merle. In America the name is given
   to several birds, as the Quiscalus versicolor, or crow
   blackbird; the Agel[ae]us ph[oe]niceus, or red-winged
   blackbird; the cowbird; the rusty grackle, etc. See
   Redwing.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Turdus merula
    n 1: common black European thrush [syn: blackbird, merl,
         merle, ouzel, ousel, European blackbird, Turdus
         merula]