The Use, and Misuse, of the Subterminal Black Tail Band to Age Female American Kestrels

The tail feathers of female American Kestrels (Falco sparverius) are rufous-brown with black bands down the entire length. There is considerable individual variation in the width and shape of these bands. The width of the most distal (subterminal) black band relative to the width of the next proximal black band may change with age. Published empirical data show that juvenal rectrices have either narrow or, less commonly, wide subterminal bands while adult rectrices consistently have wide subterminal bands. Here we review the literature about this characteristic and discuss how it has been used, and potentially misused, to age female American Kestrels.