Typically, the falcons do not begin incubating until the third or fourth egg arrives so that all the eggs hatch about the same time. Otherwise, the bigger, first-hatched chick would have an unfair advantage at feeding time over the smaller, last-hatched chick. You will see both adults sitting on the eggs at times over the next few days but incubation does not begin in earnest until the laying period ends.
The eggs are capable of withstanding temperatures below freezing. The chicks do not develop much inside the egg until incubation begins. Occasionally, the eggs will appear to be left alone for short periods but, even when the adults are out of camera range, you can rest assured that at least one is always nearby to protect the nest.
|Mom, serious about incubation.|