[Mystery birds] A pair of Dickinson's Kestrels, also known as White-rumped Kestrels, Falco dickinsoni, photographed in Mikumi National Park, Tanzania, Africa. [I will identify this bird for you in 48 hours]
Nikon D300s, 600 mm VR lens with 1.4 x extender ISO 800, f/7.1, 1/400 sec.
Please name at least one field mark that supports your identification.
White-rumped Kestrel's closest relatives are the Grey Kestrel and Banded Kestrel, and the three are sometimes placed in the subgenus Dissodectes. I've sent email to the photographer, asking him how he distinguished this bird from a grey kestrel, so check back to see what his answer is.
Dan added a comment below and sent me another photo of one of the above birds to help you better see how he made his ID:
[Mystery birds] Dickinson's Kestrels, also known as White-rumped Kestrels, Falco dickinsoni, photographed in Mikumi National Park, Tanzania, Africa.
The general shape of the bird should be a good clue. It's nearly identical to that of a common North American member of the same genus that's found from the Pacific coast all the way to Amherst, MA.
It's a Grey Kestrel. A uniformly grey falcon, with yellow legs, feet, eye-ring and cere.
Polihierax semitorquatus, pygmy falcon: yellow eye patch.
I have a mystery bird to get identified. I can't seem to find where to post the photo. It was in the gulf of mexico near Indian Rocks Beach, in Florida.
F. ardosiacus is more uniformly colored, with a much darker head. F. dickinsoni also has a strongly barred tail, which can be seen on the lower bird.
I primarily use Stevenson and Fanshawe's book, "Birds of East Africa" as my reference for Tanzanian birds. Dickinson's Kestrel has a pale gray head contrasting with the body, as well as a strongly barred tail. Other photos show the barred tail better than the one submitted.