Here's a scholarly research paper I found online about humidity in Coturnix incubations: http://www.lrrd.org/lrrd21/3/roma21038.htm I'll cut/paste the abstract here, but not the article, since that would violate copyright: "Abstract This research aimed to verify the effect of relative humidity during incubation of Japanese quail eggs on hatchability, egg weight loss, hatch weight, and embryo mortality. A total of 150 Japanese quails (Coturnix japonica) were used for egg collections. The eggs were divided into three experimental groups: low humidity group (36.05±6.06% RH; n=100), intermediate humidity group (52.25±4.99% RH; n=100) and high humidity group (76.50±4.44% RH; n=100). Each group of eggs was incubated in an individual incubator, according to its experimental relative humidity during incubation. Incubation process was done by automatic incubators with temperature of 37.5°C, and egg turning every 30 minutes. At the 15th day of incubation (360h) egg turning was stopped and the eggs were transferred to the hatcher that maintained the same temperature and relative humidity until hatch. All eggs were weighted on 1st, 5th, 10th, and 15th day of incubation and quail chicks at hatch. Japanese quail eggs incubated at the lower humidity presented the highest level of hatchability (79%) compared to intermediate and high humidities. Egg weight loss was respectively 11.96%, 8.94%, and 4.89% for low, intermediate and high humidity groups. Futhemore, the weight at hatch was influenced by the different incubational humidities. Embryo mortality presented no statistical difference among the different humidity treatments."