Molecular Testing to Detennine Sex of Northern Saw-Whet Owls

Ongoing studies are being conducted on migration habits of saw-whet owls, a pattern which was previously unknown to include states such as Virginia. By understanding sex ratios, researchers can establish important population statistics and hypothesize about population growth rates. The current factors which determine the sex of the northern saw-whet owls is in question. Research stations are by in large taking a measure of body mass and wing chord ratio, which is being used as a morphological method to determine sex. However, these characteristics have been critiqued in the literature since recent feeding can greatly impact weight. I hypothesized that molecular tests will give nearly one hundred percent sex identification because sexual characteristics in birds are determined by the presence of two W chromosomes in males or a Z and W chromosome in females. Total DNA was purified from owl blood samples and prepared for polymerase chain reaction (PCR) amplification of a region to determine Wand Z chromosome content. Using gel electrophoresis, amplified DNA fragments were separated according to their relative sizes, with a single 400 bp band (WW) in a male sample, or a pair of 400 and 600 bp bands (ZW), which indicated a female sample. The results obtained in my molecular tests were for the most part in agreement with field data; however, DNA analysis of some samples changed the sex assigned in the field and in one case, allowed me to sex an individual from the ambiguous category of the morphological charts