I thought I would share my observations of how I age female kestrels, since it seems to be hard for a lot of people. The sub terminal black band being close to equal size to the bands above it can be a good indicator of passage in a lot of birds but some, like the one above, its pretty hard to tell. I've trapped a bunch over the past couple of years and I only counted passage by stress bars across the tail, then I compared them to known hags. There are a couple of stand out indicators between the two. At least from the birds I've trapped in Oklahoma. One is the overall color. Passage birds are a dull orange compared to hags that are more of a reddish orange. The black markings on hags are much sharper than that of the passage birds. The most distinguishing feature that I have noticed is the color of the primaries and secondaries. On the hags they are almost black and on the passage birds they are more brown. Also the Hags have a distinct white trailing edge to their primaries and secondaries, where the passage birds have a more tan trailing edge.