If someone purposefully obsessed over a certain animal how much might it impact their chances of rebirth as that animal? And im looking for a buddhist perspective mainly, preferrably the views of various traditions. 

But yeah, if i (for example) wanted to be reborn as a bird, would obsessing over and even acting birdlike, practicing a birdlike mentality, living on seed (grain)... even dying with bird thiughts in full swing... stuff like that, would the attachment and desire cause my mind to reform into a bird?

(Sidenote- i do not want to be reborn as a bird. It is a valid point i am trying to understand in a round about way).
I think Buddha has answered this question perfectly. You can find the full answer here. Two people went and asked the same question from Buddha. One of them was practicing like a dog and the other one was practicing like an ox. Here's the answer to the one who was practicing the dog duty by the blessed one.


  .. someone develops the dog duty fully and unstintingly, he develops the dog-habit fully and unstintingly, he develops the dog mind fully and unstintingly, he develops dog behavior fully and unstintingly. Having done that, on the dissolution of the body, after death, he reappears in the company of dogs. But if his view is such as this: 'By this virtue or duty or asceticism or religious life I shall become a (great) god or some (lesser) god,' that is wrong view in his case. Now there are two destinations for one with wrong view, I say: hell or the animal womb. So, Punna, if his dog duty is perfected, it will lead him to the company of dogs; if it is not, it will lead him to hell.


So I think it's not difficult to deduce what happens to the person who tries to act like a bird.