The soft yellow-green background is a subtle but effective contrast to the rich lemon feathers the birds.
The tiny jewel-like lichen covering the branches and the green sprouts on red twigs adds tremendous value.
By using an ISO of 100 you were forced to use a fairly slow shutter speed which increases the risk of subject movement. However, the image appears sharp.
Were you using the ultra-low ISO to get the maximum dynamic range and minimal noise out of the fancy sensor in your D800?
One fine image! Great perch, good eye contact with both birds, and a yellow BG that matches the birds perfectly. Not sure about your decision to go with ISO 100, although it worked well in this frame. I'd probably have gone with ISO 400 and a faster SS with additional DOF.
This is one sweet image, Greg. Just love the design. Beautiful perch, excellent wheat bg, and two perfectly sharp birds. And all of that without crowding the frame or making it look busy. A big winner in my book.