Sex Determination

Most species of owl do not exhibit sexual dimorphism in their plumage. This makes determination of sex much more difficult in owls than in those bird species that exhibit plumage dimorphism by sex. The ability to determining the sex of a bird in the hand is an essential skill that one must posses to band birds. Knowing the sex of an individual owl allows researchers to examine important biological questions such as differential migration by the sexes. For many years it was not possible to assign sex to owls based upon external characteristics. The availability of modern DNA analysis techniques has made it possible to develop methods based upon external measurements to assign sex with acceptable reliability to owls and other species of birds that do not exhibit sexual dimorphism in their plumage. This section of the Project Owlnet web pages includes information essential to accurate determination of sex in migrant owls. Presently detailed information is only available for the Northern Saw-whet Owl. As the web site grows and information is contributed by other owl researchers subpages will be added for additional species.