This system is not perfect. Remember that some eggs were incubated to some extent before the clutch was complete. These eggs would be further developed than those deposited at the end of the laying period. And despite the hen’s diligence, some eggs may still develop slower, or faster, than others.
Near hatch, a couple of intriguing things occur to adjust for these possibilities. For one, the embryos begin to communicate with each other by emitting clicking sounds that cause the slower embryos to quicken their metabolism and the development of their tissues. The hen also starts to give quiet clucking sounds that may help synchronize hatching and, most importantly, are the first communication between the hen and her soon-to-emerge brood. This is known as imprinting and assures that the hen is able to maintain a cohesive brood that responds to her leads as to whom to follow, where to feed, and when to avoid predators.
The hatching period lasts several hours. Some ducklings may be hatched and dried out before the last ones have hatched. All the ducklings must have enough nutrients to sustain them between the nest and the first brood pond, a period of time that could last up to a full day in bad weather. The necessary energy and nutrients are provided by the remaining yolk, which is absorbed into the gut and used until that first meal is available.
In the end, most ducklings will be dried out and ready to leave the nest all together when the hen gives the right signal. This adventure usually begins in early morning, as the hen and her brood head for the pond she has chosen for the ducklings to seek their first opportunity to feed and get water. The hen does not feed the ducklings. She only takes them to the places she has found where they can feed themselves. While the ducklings are still very small, she may protect them from inclement weather by brooding them under her body, but they soon outgrow this possibility. Not surprisingly, the nesting period and the first hours and days after hatch are when the highest mortality rates occur for all waterfowl.
This intricate sequence of events is repeated every nesting season. Each species may work things out a little differently, but all these steps are critical and can only be successful when the habitats the birds use provide all the needed elements.
Dr. Bruce Batt recently retired after serving for more than 15 years as chief biologist at DU's national headquarters in Memphis.
Most prairie ducks will renest if their first nest is lost to predation or some other cause. Mallards have been known to make as many as five nesting attempts during one breeding season. Pintails, on the other hand, may renest only once, and often they do not renest at all. However, biologists have discovered that ducklings from later nests have a reduced probability of surviving until the following nesting season. This could stem from several factors, such as a shortage of the full complement of nutrients from the hen to assure the highest quality eggs, ducklings hatching past the optimal time for food availability in brood habitat, or too little time for the ducklings to grow adequately before fall migration.