Mountain Oriole with what on his foot?

I was experimenting with the new / old 600 5.6 ED. Caught this

slightly fuzzy moment of a Mountain Oriole. When I enlarged and

looked at the shot, it appeared that something manufactured was

attached to the bird's left foot. Anyone seen anything like it?

Unfortunately it  is  not  sharp, it  is  not  the lens, it  is  you.  Nice shoot, the take-of  of the bird  in motion,  it same  to me, slow shutter speed  and hand motion, camera shake. What I like on this  shoot is  the  bird claws  just  released for the take of. To bad  it  is not  sharp.

I like to hear, how  do  you like  the Nikon Df. I haw  one  beside  the D3s  and the D4, but lately  using the Df most of the time. The quality of the images, technically,  better, IMHO,   then the  previous  cameras of my.

-BLM.

Bela, I knew it was not the lens, I find it very capable.  Unfortunately, to get the best from it, I need to use a tripod, which I am not fond of, or monopod which I am just learning.  If time and practice work, I'll eventually get there! Best, Sandy.