What are the chances that an egg laid by a duck hatches, develops, and lives to see its first birthday? As you might assume, the odds are not good.
I was reminded of that stark reality recently when I noticed a hen mallard leading her brood to water. The hen had all her ducklings in a row and all was going well. But as soon as the hen and a couple of duckling hit the water a mink, seemingly out of nowhere, shot out into the water in hot pursuit. You could just about see the mink weighing which duckling to pursue. The hen got up and flew at the mink a couple times, but it only delayed the inevitable. To quote Tennyson, it was “nature, red in tooth and claw.” We all know these kinds of things happen, but we seldom see them.
That episode led me to read up on nesting success and duckling survivorship. As with other birds, the journey from egg to young to adult is fraught with danger.
A hen mallard may lay anywhere from 1-13 eggs or more, and incubation time is about one month. It should be noted that if all the eggs are destroyed, she may re-nest. As one might expect, a wide range of highly variable factors influence how many eggs actually hatch. Examples of those factors include the quantity and quality of nesting habitat, predation, disease and parasites, storms, human activity, and factors relating to water quality, quantity, and distribution. As you might expect, predation has been shown to be the major factor in nesting failure. Common nest predators of ducks include skunk, raccoon, and fox. A nest success rate of 15% is often used as a rule of thumb for maintaining a mallard population. The percentage however, differs between species. The rule of thumb for pintails, for example, is 20%.
But once the egg has hatched, what is the chance the ducking will survive? Duckling survival is not well understood. And it takes around 50-60 days until the ducklings can fly. That is a lot of time for things to go badly for them. It has been estimated that somewhere between 10%-70% will fledge. But an estimated 30-50% of mallard ducklings will survive their first year. For a duck egg to hatch and the duckling to live to be one year old is likely much lower.
