I was reading that there was a Manga about a curse between a knight and a princess and by night, the knight would turn into a Wolf and by day the Princess would be a hawk and that's what possibly this new Zelda is based off of...there was even a hawk flying onto Link in the trailer and 'Zelda' was outside when it was dark (zomg twilight?). I'll find the link in a bit.

http://cube.ign.com/articles/615/615045p1.html

"Of course, IGNcube has speculated for a great while that Link would likely be able to change into the beast, but the latest trailer is the first official proof of the action. There are all sorts of theories about how this mechanic may play into the game. A search of the title Twilight Princess on the Internet, however, reveals some interesting information. Apparently this is also the name of a Japanese manga which was inspired by the movie Ladyhawke. That film tells the story of a knight and his lady ruined by a horrible curse. The knight is forever cursed to transform into a wolf with the moonlight, just as the lady is cursed to change into a hawk at the first sign of sunlight. There is a possibility, albeit far from proven, that the new Zelda may mirror this storyline. Footage from the latest trailer seems to back this theory, as Link can be seen carrying a hawk on his arm as he explores certain areas. If Twilight Princess does follow the Ladyhawke storyline, that hawk would of course be Zelda."