What is birds nest?

What kind of birds nest could this be?

• in school we have to do this field study and we took a picture of a large nest in the trees, we live in central alberta, it was near a small lake and there was a walking path every close, at first i was thinking it would be an owls nest but would they put there nest so close to a busy path, then i was thinking it could be a magpie or a hawk or something, the nest was pretty large and it was about half way up on the trees around (the nest was at the top of a smaller tree, could anyone tell me if it would be a owl or hawk or magpie, based on the high and closeness to the path)

• Answer:

  um well chances are its looks like a ball of leafs its probably a squirrels nest soo