Current 2013 AVMA Guidelines for Euthanasia of Animals requires or suggests 10-30% displacement of air with CO2 when euthanizing all species with CO2 overdose. However, the majority of literature supporting the 10-30% slow displacement is based on small rodent studies. Further, sections of the AVMA Guidelines suggest that displacement rates of higher than 10- 30% for avian species is more humane, but references supporting other displacement rates are lacking. Additionally, there is a lack of literature describing optimal CO2 euthansia techniques in each avian species commonly used in research. We often receive feedback from researchers, husbandry technicians, and veterinary staff questioning the appropriateness of 10-30% displacement of air with CO2 during euthanasia in avian species because time to unconsciousness is perceived to be longer than in rodent species, possibly resulting in increased distress. This study primarily aims to determine if 10-30% displacement of air with CO2 is a humane method of euthanasia in avian species commonly used in research. A second aim is to determine the effectiveness of ethanol overdose for euthanasia of commonly used avian species.