Migrating turkey vulture
The annual Raptor (aka Birds of Prey — eagles, hawks, falcons, owls and vultures) migration is in full swing. The birds of prey are migrating north to their summer nesting grounds. The raptors fly up the hog back for several reasons. First, it is an easy marker for them to follow — a constant ribbon of rock from New Mexico into Wyoming. Second, the sun warms the rocks and provides up drafts. These up drafts give a little extra lift that the heavy birds of prey use to gain altitude. With the gift of lift, the raptors can soar for more miles every day.
Scientists take advantage of the concentration of raptors. There is a monitoring station perched on top of the Dakota Hogback at Raptor Ridge, just on the east side of Co Hwy 93, just south of the I-70/ Co Hwy 93 interchange. There is a parking lot at the base of the hog back, across from Mathews-Winters Open Space. http://jeffco.us/open-space/parks/matthews-winters-park/
Migrating Cooper’s Hawk
Migrating red-tailed hawk
Scientists from the Denver Museum of Nature and Science initially manned the observation station, but budget cuts took their toll, and the job was passed on to Hawk Watch volunteers from the Rocky Mountain Bird Observatory. http://rmbo.org/v2/web/getInvolved/hawkWatch.aspx These hardy folks volunteer to count the raptors as they fly overhead. Not a bad gig when it is nice out, but in wind or cold, it takes true dedication.
But their work pays off, and you can see it in their reports. Since they started watching at the beginning of April, almost 400 birds of prey have been spotted cruising over the hogback. https://groups.google.com/forum/?fromgroups#!topic/cobirds/N7YwWW90D3k
Hawk Watch will continue counting raptors through May. Go up and see them and spot some hawks flying by.
Colorado In Depth and At Altitude 
Saw a beautiful all snow white raptor with black wing tips and a large black mark on the underside of each wing. I was in the white river national forest at about 10,000 feet elevation and the bird was soaring above me in a circular pattern. Has anyone seen this species?
Hi, Kevin! Thanks for contacting me.
Sounds like you had an awesome trip in the White River. You don’t mention when you were up there, so I am going to give you different answers from different assumptions.
Assuming you went around September or before, my first guess is an Osprey.
https://www.audubon.org/field-guide/bird/osprey
My next guess would be a Swainson’s Hawk. In Colorado, Swainson’s have white wings and underbellies, with dark wing-tips. However, they always have a chocolate “bib”, on their chests. https://www.audubon.org/field-guide/bird/swainsons-hawk#photo3
But if you were just up there in the last couple of weeks, it being either an Osprey or a Swainson’s becomes a little problematic. The problem is that they migrate, and should be in Central America by now. But this has been such an ominously warm fall, who knows? Maybe one decided to stick around after everybody else left.
My final guess is that it was a Red-tailed Hawk. But wait, you say, it didn’t have a red tail. Turns out that red-tails are so variable that every once in a while, you’ll get one that is almost all white one. AND they are the most common raptor you will normally see in western Colorado at this time of year. https://www.audubon.org/field-guide/bird/red-tailed-hawk#photo18
https://www.audubon.org/field-guide/bird/red-tailed-hawk#photo12
If you want to investigate further, you might consider sending an email to the nearest Audubon chapter, and seeing if they can help narrow it down for you.
https://www.audubon.org/about/audubon-near-you?site=rockies&nid=5691
Again, thanks for stopping by my blog. Happy birding!
Amy