Incubators in the bird world


Picture of a great crested grebe incubating eggs.

Most birds are themselves incubators.

They brood their eggs with heat from their own bodies.

But feathers can be a problem.

They are excellent insulators, and very little body heat can get past them to incubate the eggs.

For many birds it is a built-in answer: brood patches.

Several days before the first egg is laid, the down feathers on the breast are molted, then the blood vessels in this area increase in size and number, the skin thickens and swells.

As the bird settles on the nest to brood the eggs, it fluffs out its breast feathers and shuffles about until the bare, super warmed brood patch is next to the eggs.

Or brood patches, for some birds have three of them.

Once these heat pads touch the eggs, incubation begins.

But not all birds have brood patches that appear automatically.

Ducks and geese, for example, pluck the down feathers from their breasts to bring their skin in contact with their eggs.

Other birds use their feet as incubators.

Picture of a blue footed booby.

The blue-footed booby wraps its brightly colored feet around its single egg, and the large webs, through which warm blood circulates rapidly, are just as effective as the brood patches of other birds.

We hear so much about mother love, but when we turn our attention to the emperor penguin, it’s time for father love to take a bow.

Picture of emperor penguins.

In the depths of the Antarctic winter, the female lays an egg and immediately returns to the sea to eat.

Papa, however, is left holding the egg on his webbed feet—feet richly supplied with blood vessels and therefore quite warm.

He next drapes over the egg a fold of skin that serves as a brooding pouch.

It fits over the egg so snugly that the egg remains tucked into its warm incubator “nest” even when papa walks about.

Temperatures drop to -76° Fahrenheit (-60° C.), icy blizzards rage for days, but papa faithfully incubates the egg on his feet.

Three months, and not a bite to eat!

Mama, however, hasn’t forgotten.

After the egg hatches, she returns to feed her family with predigested fish from her stomach, then takes care of the chick while papa heads for the sea to feed.

Some birds use ready-made hot spots as incubators.

The maleo on the Indonesian island of Sulawesi lays its eggs on the slopes of volcanoes, where the ground is permanently heated by volcanic steam.

Picture of a maleo bird.

Other maleo on the island use the black volcanic sands at the heads of beaches.

They bury their eggs in the sand, which, being black, absorbs heat for incubation.