I’m pretty sure this has to be a Harris’s due to the white band on the base of the tail. It wouldn’t be the first time one was in CO, we had a confirmed one in Fort Collins for several weeks this spring. Unless there’s a morph of another I’m unaware of that has that white band.
Young female Harrier caught in a mist net during bird banding operations. She's fine, was freed from the net quickly and released unharmed. A pair is known to breed here, so she may have been born on Monomoy.
First hawk I saw this year while out walking the dog.