Kestrel or Merlin?

I photographed this small hawk at the top of Whistler Mountain in Jasper National Park this weekend. Likely a Kestrel, but the pale coloration has me wondering. The mustache is fairly distinct supporting Kestrel, yet the bird also seemed larger and swifter in flight than the Kestrels I have seen. He/she was surfing along a hillside and flew very near by my head at a high rate of speed, very cool. Anyway, just want to be sure so I'll "ask a friend" as they used to say in Who Wants To Be A Millionaire.

American Kestrels are pretty variable, Gary. This looks like a male AMKE to me. BNA says,

Breast, belly, and flanks vary from nearly white to reddish-buff, but typically much lighter than dorsum. Ventral markings also highly variable, but typically with narrow shaft-streaks on upper breast, gradually becoming heavier, rounder spots on flanks. Tail variably rufous dorsally, much paler ventrally, usually with a single wide, black subterminal band. Tip of tail may be white, buff, gray, pink, rufous, or a combination of those colors.

Seems to meet the description of the paler forms of the species.

This looks very much like a Prairie Falcon to me Gary. Note in particular the dark underwing of the right wing. I just read your description of how you saw it and that it seemed larger and faster, this is usually how you see a Prairie Falcon surfing along a ridge line. In fact I'd be willing to say this is a Prairie Falcon for certain.

I shouldn't argue with the master, but Nate, wouldn't you expect to see at least a hint of those big feet - 2-3 times the size of a Kestrel's - showing in a shot from below?

I can see what you mean Jim but does a kestrel have this underwing pattern? The bird you posted shows the same underwing pattern of the bird above. I certainly wouldn't consider myself a bird id master but I just can't get anywhere near American Kestrel on the bird posted. The pale coloration would support Prairie Falcon as well. I've seen a lot of both species and my immediate reaction was PF, but who knows?

Here's what is definetly a Prairie Falcon from Malheur and the feet are more prominent here.

Take a look at this female Kestrel photographed by Jim Zipp for comparison of the underwing pattern and the tail. It doesn't have the diagonstic dark pattern of the Prairie Falcon and it does have a somewhat prominent subterminal band that is lacking in all 3 birds above.

http://www.naturephotographers.net/imagecritique/ic.cgi?a=vp&pr=16033&CGISESSID=64e14180d0ec89deeb00f18f3424bcba&u=19679

By the way you can rule out Merlin because they have thick dark bands on the tail.

Thank you Jim and Nate for your assistance. Sorry I don't have any dorsal views, just variations on the ventral view. I can add that the dorsum was very pale, in the bright sun I saw almost white as it zoomed by. Again my impression was that it was quite a bit larger and heavier than any A. Kestrel I have seen. I saw a Prairie Falcon a couple of years ago close up in a rehabilitation centre and it does fit; it just never crossed my mind to consider this much less common species for this area. I had a look in a book entitled "Birding Jasper National Park", p. 53 states regarding the Whistlers Mountain location that, "During late August there is a possibility of seeing sharp-shinned hawk, northern harrier or prairie falcon migrating along the timberline ridges." It's early but does at least indicate they are seen at this site.

My first impression with my first glance at your picture?
"Black armpits! Prairie falcon!"
The first bird I flew as an ignorant, aspiring falconer in 1954 was a "sparrowhawk"....,now termed American kestrel, and in the 60s and 70s flew several prairie falcons. That's a prairie!

Dave Graham, East River, South Dakota