you will want a stbile temp, are you turning it regularly?Oh and I simply too a Styrofoam cooler with a lsmall heater in front of a hole carved on the side and I have a very precise laser thermometer to double check the temperature, I should maybe get a light bulb but as the temperature is pretty stable and the heater provides ventilation and I can control the intensity, I am wondering if I should or wait to order an incubator...
it does look like it is developing
sounds like you will want a way to get the humidity up for lock down
do you know what kind of ducks are in your area?