The chart shown below lists the major incubation factors and the values of each that produces the best incubation conditions for the species of birds shown. Improper control means that the temperature or humidity is too high or too low for a sufficient length of time that it interferes with the normal growth and development of the embryo. Poor results also occur from improper ventilation, egg turning and sanitation of the machines or eggs. Prolonged periods of high or low temperatures will alter hatching success.
High temperatures are especially serious.
A forced-air incubator that is too warm tends to produce early hatches. One that runs consistently cooler tends to produce late hatches. In both cases the total chicks hatched will be reduced. Maintain a still-air incubator at 102 degrees F. to compensate for the temperature layering within the incubator. Obtain the proper temperature reading by elevating the bulb of the thermometer to the same height as the top of the eggs when the eggs are laying horizontal.