As we watch the two adults putting in so much time incubating their four eggs, we can think about how incubating eggs is the result of lightening up airframes.
As large, long-lived social mammals, we have the luxury of carrying our developing young (usually one at a time) within our bodies. We call this pregnancy of course.
Falcons don't have this advantage because they fly. To fly, they must obviously maintain a very light weight. There is no way they could ever carry four eggs inside. So they must develop their young externally and away from the body (incubation) in the form of large eggs produced one at a time. This all involves a nest site, a scrape in the soil or gravel, shared incubation duties for a long period of time by both adults and ultimately, the hatching process.
So keep in mind that small falcons are assembling within those reddish-brown eggs right now. Eyes are developing, skeletons, feather follicles, and talons are all taking form cell by cell. It all takes time.
But they will all be thrust out into the wide world very soon now....
