What Breed Is My Dog?

My puppy is around 8 months old. She was found behind my aunt's house in the woods in a box with her brother. I took her in as my own. My vet guesses she is some kind of Alaskan breed, but I've heard anything from Australian Shepherd to Border Collie to Pit Bull. She's white with black spots and has barely any hair on her ears and she has these light gray, sometimes blue, eyes. She weighs 33 pounds, but it very skinny and tall with long legs. She loves to chase things like birds and is very springy and jumps very high. We have no idea what she is mixed with.