Additional Size Comparison Pics
During incubation, the adult falcon will part its breast feathers in order to obtain skin-to-egg contact to help keep the eggs at the proper temperature for development. For every action there is a reaction and if you watch closely, you can tell when this is happening. When you see the adult wiggling and its back feathers raising up while it is settling down on the eggs, that is actually the opposing reaction to the falcon spreading those breast feathers. So even though we can't directly see the skin-to-egg contact, we know it is happening by what the back feathers are doing.
Here are a couple of additional views of the adults incubating to again show how much larger Durand is than the male. She really fills up the nest box and rarely can you see the gravel by the back wall when she is on the eggs!
Don't forget to check out the ODNR, Division of Wildlife's website for more information on peregrine falcons!