Neysa Wilhide, age 11, of Asheville, North Carolina, for her question:
Why are birds' eggs different colors?
There was a time when nature lovers collected and displayed bird eggs, with the proper name and address of each species. Nowadays, thank goodness, we know that this is unfair to the bird world. The youth generation of nature lovers is dedicated to saving all our wild creatures from encroaching extinction. Besides, we enjoy them more when we observe them as friends, from a safe and polite distance.
Modern ornithology students refuse to sacrifice precious bird eggs to build private collections for themselves. They prefer to admire true to life pictures in bird books and in nature films taken in the field. The obvious reason why bird eggs come in such a variety of plain and fancy colors seems to be camouflage. But as usual, in nature there are many exceptions that appear to disprove the general rule.
Imagine a ruffled grouse, crouched on her earthy nest. Her brown speckled feathers match the fallen leaves on the ground and blend in with the dusky brown shadows of low hanging boughs. If she leaves her shallow, leaf lined nest for a moment, her buff colored eggs also blend invisibly with the surroundings.
The killdeer parents tend four buff colored eggs, all freckled with brown. The nest is a bare hollow on sandy or stony ground. You could stare right at it and mistake the eggs for pebbles. The loon lives by the water and uses plant debris to build a large, shaggy nest on the ground. Her two big eggs are greenish brown, lightly speckled with dark spots. Picture the shadowy shades of the green brown sedges and weedy reeds and you will see how well her eggs get lost in the scenery.
A robin's nest is a brown half shell of dry mud, reinforced with twigs and twine. The smooth eggs are an unforgettable shade of plain blue. Such an eye catching color scheme seems conspicuous. But the nest is perched high among the boughs, where the spring, sunshine casts dusky shadows and reflects patches of blue sky from the glossy young leaves.
Many birds that hide their nests in dark crevices lay plain white eggs. The screech owl's shabby nest is concealed high in a hollow tree. The barn owl often nests in an underground burrow, as does the jewel toned kingfisher. All these birds lay plain white eggs, safely hidden in the dark from prying eyes.
Most, but not all, bird eggs are camouflaged to match the subtle colors of their natural surroundings, and most plain white ones are hidden in dark nests. However, the house wren's nest is a dark hollow and her pale pink eggs are spotted with reddish brown. The tiny hummer lays plain white eggs in an open topped tree nest.
Most bird nests are fragile, and all sorts of predators relish the precious eggs. Camouflaged colors can fool the eyes of egg eating birds, but many egg eaters are color blind mammals. Perhaps these foes are fooled by the speckled designs of light and dark tones. But nobody can explain why certain birds lay eggs that do not match or blend with the scenery at all.