Although the occasional determined hen persuades us to let her incubate a few eggs most of our eggs are artificially incubated. We mostly use Brinsea incubators with humidity management. We also have a few King Suro incubators from r-com. We have had much better success with Brinsea's Octagon 20s than the larger 40s. We found the temperature in the 40s to vary too much between the edge and the centre of the incubators. We still use them as hatchers as the temperature does not have to be quite so precise at the hatching stage. The King Suros are great little incubators while they work but they don't seem to last long. We've had too many break downs with them to continue using them so last year we bought another updated version of the Octagon 20. We had a good start with it so hopefully it will continue to run well for 2017.
We have a heater on a thermostat in our incubation room which helps keep our small incubators stable. Having a number of small incubators instead of one large one works well for us as we have many different species of pheasant and eggs from some need more humidity than others so we have each incubator at slightly different settings. Although the humidity differs from species to species or egg to egg, the temperature in every incubator is set at 37.7°C. If the humidity is not set correctly for an egg it will either lose too much weight or too little. Yes, it sounds strange but eggs actually become lighter as the embryo inside developes. We weigh our eggs often throughout their incubation to see whether we need to adjust their humidity slightly or move the egg to a different incubator with a higher or lower setting. Rob Harvey has written an extremely good book called "Practical Incubation" which is well worth buying. "Pheasants of The World" by Keith Howman is another good book from which we got graphs for charting weight loss of eggs from laying until hatching. This gave us the information needed during incubation. If eggs are not losing enough weight (and moisture) we need to lower the humidity slightly or raise the humidity if they are losing too much weight (and moisture). The humidity in the incubators can vary from as low as 10% relative humidity (RH) to about 55% RH. It is definitely trial and error but hatchability has been very good using graphs to determine humidity.
It is certainly money well spent to buy the most precise thermometers, scales etc. you can. The thermometers we use are very accurate but they are not actually expensive (usually around £4 each). They are ones sold in the chemist for medical use and are accurate to 0.1°C. By having a handful you can check they are working properly if they are all reading the same. The correct temperature is of course the most important factor in the incubation process. Only adjust temperature a little at a time. If your chicks are hatching late then you should raise the temperature. If they are early however the temperature is too high.
As well as weighing eggs we also candle them during incubation. When we first started doing this we used a candling lamp bought especially for the job but the brinsea one we got didn't last very well and when we wanted to try a different make we couldn't find one narrow enough for our liking. We now use a torch instead with a narrow beam and a strong led light. They are excellent to see into the eggs and unlike the brinsea lamp they are battery operated rather than mains so there's no wire.
We have found that, rather than putting eggs in the hatcher two or three days before hatching, we have better results when the chick has pipped internally (usually 24 - 48 hours before hatching). This might be because our incubators are not on rollers but only tip slowly from side to side. The chicks seem to manage to position themselves for hatching perfectly well. We put them in a hatcher so we can increase humidity drastically to around 70%RH. We also decrease the temperature to about 37°C - 37.4°C from 37.7°C. Having the newly hatched chicks separate from the eggs also helps in the control of bacteria. We have had a lot of success but we are always learning. If anyone would like to send us information of their own experiences we would love to hear from you.