A mallard duckling and an infant songbird tumble out of their eggshells in their nests on a fine spring day, but their life experiences over the next few weeks will be vastly different.
Ducklings emerge in a ground nest with eyes wide open, covered in fluffy yellow down and able to stand on sturdy legs. Their mother is very attentive during their first day, keeping her brood warm under her body and spreading her waterproofing oils onto their downy feathers. Within a day, the ducklings are waddling behind her, heading for water.
Duck broods are too large — up to 12 chicks — for a single parent to feed individuals. Instead, ducklings watch their mother closely for clues about what to eat. They huddle under her at night and during cold spells for some days and her parental duties won't entirely end until they can fly, at about nine weeks of age.
In contrast, at hatch time, the tiny songbird chick's eyes are sealed shut, with a few wispy pieces of down on its head as it lies helplessly at the bottom of the nest. The infant songbird requires intensive parental care, including many feedings a day, for nearly two weeks before nestlings gain the feathers, strength and maturity to leave the nest.
Why did Mother Nature create this dual system, where some bird youngsters "hit the ground running," while others are born blind and helpless? As it turns out, both the duck mother and the songbird parents spend about the same amount of time bringing their youngsters to the fledging stage. The main difference is in where that development occurs, and a great deal of it relates to predation pressures.
The mother mallard will sit on her fairly large eggs for about a month as the embryos slowly develop. Duck youngsters feast off large yolks packed with nutrients and accomplish much of their development inside the egg, Their bellies will still have some yolk remaining after hatching, providing a cushion during their first several days of life.
Because their mother is so attentive to her nest, ducklings aren't in great danger until they hatch, but then they must leave the nest as soon as possible to avoid the many predators (foxes, raccoons, crows, etc.) that enjoy dining on ducklings. (There are dangers in the water, as well, in the form of turtles and large fish.)
On the other hand, songbirds produce fairly small eggs, with an incubation period averaging about two weeks. After the young hatch, parent birds rush to find food from dawn to dusk, since adults bring in every morsel consumed by their nestlings. On a steady diet of caterpillars and insects the nestlings grow rapidly, increasing their weight tenfold and producing a full coat of feathers in less than two weeks. They need to grow fast and get out of their nest fast because nests are dangerous places, constantly under threat from predators like squirrels, raccoons and others.
