The plumage of the Red-tailed Hawk has lots of variation. Even if your someone who loves to study hawks, you may want to pull your hair out if looking at a bird that doesn’t fit the range of variation you know to occur for a specific race of Red-tail. But this variation can be a good thing, it is invaluable when you want to confirm that an individual bird is the same one you are seeing day to day or year to year.
When trying to ID an individual bird on separate occasions, you need to consider several things. You can’t rely on one characteristic, some birds may show a distinct trait, but many will not. I use a form sheet I made up with a space at the top for a name I give each bird and the date photographed (categories below). The form just helps me keep things straight, so I don’t overlook anything. An example of the form is shown below. The form helped me prove that a pair of breeding birds that occupied a specific territory in summer weren't the same birds occupying that exact location in winter, as another local birder suggested. We know that some Red-tails remain on territory year-round, while some migrate south and are replaced by other Red-tails. Noting distinct plumage traits has also helped me verify when instances like this occur; and that a certain Red-tail has come back to the same patch every winter since 2004 -- check out the pictures below of one individual (all photos by Derek Lyon).
"Click" to enlarge form