tags: Crested Caracara, Southern Caracara, Common Caracara, Mexican Eagle, Polyborus plancus, birds, mystery bird, bird ID quiz
[Mystery bird] Crested Caracara, also known as the Southern or Common Caracara, or as the Mexican Eagle, Polyborus plancus, photographed at Smith Point Hawk Watch, Texas. [I will identify this bird for you in 48 hours]
Image: Joseph Kennedy, 30 September 2009 [larger view].
Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/1250s f/8.0 at 1000.0mm iso400.
Please name at least one field mark that supports your identification.

Turkey Vulture. Field marks are the black wings with white tips on the underside and those distinctively splayed "fingertips" on the wings.
careful! take a closer look at the back end of this bird and ignore the wings for a few minutes while you examine your field guides closely. then look carefully at the pattern of "white" (silver?) on the wings ..
Another hawk!!
Actually a falcon -- Crested Caracara. The white base to the tail, the white on the head, and the white on the outer primaries all indicate this, and the dark on the belly rules out anything else that might show this combo.
I'm with psweet: Crested caracara.
(Lia, first glance said "turkey vulture" to me, too!)
Yep, Crested Caracara (or Northern Caracara) Caracara cheriway, [but formerly of the genus Polyborus]
soars with wings slightly bowed down (Sibley), dark plumage with white head and tail, and distinctive white wingtips...
The reclassification of this bird is rather complex but according to ornithologist Dave Appleton (who also operates www.gobirding.eu) the current taxonomy goes like this: