The Collaborative International Dictionary of English v.0.48:

Ern \Ern\, Erne \Erne\, n. [AS. earn eagle; akin to D. arend,
   OHG. aro, G. aar, Icel., Sw., & Dan. ["o]rn, Goth. ara, and
   to Gr. ? bird. [root]11. Cf. Ornithology.] (Zo["o]l.)
   A sea eagle, esp. the European white-tailed sea eagle
   (Hali[ae]etus albicilla).
   [1913 Webster]

WordNet (r) 3.0 (2006):

erne
    n 1: bulky greyish-brown eagle with a short wedge-shaped white
         tail; of Europe and Greenland [syn: ern, erne, grey
         sea eagle, gray sea eagle, European sea eagle, white-
         tailed sea eagle, Haliatus albicilla]