At a nearby wildlife rehabilitation center (where I have often taken sick or injured birds and animals) I have noticed a red-tailed hawk that used to be in a cage outside the front door. This bird is not able to be released back into the wild so is often seen during events held at the center during the year where the public can approach more closely and ask questions.
In cases like this with the bird in front of me, I often sketch directly into my sketchbook or do smaller studies on watercolor paper. Then back in the studio, I take more time over a detailed study like the one above, trying all the while to capture something of the essence of these magnificent birds. This watercolor study is on Arches hot pressed paper, size 7" x 11.5". Sold.