Lynda Cherner, New Windsor, New York. Unlike loons and grebes, ducks wait until all eggs are laid to begin incubating. If another egg comes on after incubation begins, the duck will lay that egg in another duck's nest. Because incubation begins at the same time for all eggs in the duck's nest, embryo development in each proceeds equally, and all eggs usually hatch within an hour or so of each other. Delays of several hours to a day do occur.
Female ducks select the nest site, usually within the home range of the drakes with which they mate.
A hen may repeatedly fly large circles around the chosen nest area both before nesting and while incubating. The nest site may be a mile or more from the water where she intends to raise her brood. The reconnaissance flights allow her to determine the path by which she will walk her ducklings to the water after hatching. Mallards have become as urbanized as northern flickers, blue jays, and American robins. Ornamental landscaping appeals to them.