Joe Kirker specializes in 1918 airmail issues. He has authored over one hundred articles, primarily on the Jenny series, and his research into all aspects of the series has enlightened many philatelists. Postal history, perfins, vignette shifts, pre-cancels, plate varieties, and SPECIMEN overprints all fall under his purview. Besides the Jenny, he collects the Canadian 1897 Jubilee Series.
Though he collected during childhood, Kirker devoted serious attention to the hobby after serving in Viet Nam. In addition to his philatelic interests, he has a passion for the Alaskan wilderness and has lived near Denali National Park. He recently retired from the steel fabrication industry.