Cooper's Hawk

Earlier this year, this Cooper's Hawk was working on building a nest in a tree near our house. I took these photos on March 23rd:

I'm still struggling with determining whether this is a Cooper's Hawk or Sharp-shinned Hawk. However, using these identification tips, I've been going with Cooper's Hawk because:

1. The tail feathers appear to be rounded as opposed to more square
2. The head seems fairly large as opposed to small compared to the body

Those are the most obvious things to me, however, on the contrary the legs appear to be pretty long, particularly in the second photo, which is more characteristic of the Sharp-shinned Hawk.

I did hear the bird make several a short chirps unlike any of the sound clips on allaboutbirds.com, however, this description from the site sounds accurate:

Males frequently make a kik call to tell their mates where they are; females make this call too, but less often.

It sounded very much like this recording from the Cornell Lab of Ornithology Macaulay Library.