The ability to determining the age of a bird in the hand is an essential skill for all bird-banders. Assigning age to migrant owls depends on patterns of flight feather molt, per Pyle (1997), and other criteria that vary by species. This section presents information essential to accurate determination of age in migrant owls. Detailed information is currently presented only for Northern Saw-whet Owls. As the web site grows and information is contributed by other owl researchers, subpages will be added for additional species.