Use of DNA analysis to identify sex of northern spotted owls (Strix occidentalis caurina)

The spotted owl (Strix occidentalis) is a monochromatic species with slight sexual size dimorphism in adults. Methods currently available to identify sex of adult owls are ineffective for juveniles. Blood samples taken from owls from the eastern Cascade Mountains, Washington were used for cDNA cloning of a Z- and W-linked gene, DZWM1, to identify the sex of adult owls of known sex. A blind assessment resulted in the correct identification of sex for all 59 owls sampled (45 subadult/adult and 14 juveniles recaptured as subadult/adult). We believe this technique can be used to identify the sex of owls that cannot otherwise be identified using less invasive morphometric methods. Both field and laboratory procedures are described.