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species of birds, in which the female is obscurely marked, that build in holes and cavities, such as our wrens, the great crested flycatcher, the European starling, the English sparrow, the bush-tits of California, and the wood duck. The female oriole is much duller-colored than her mate, yet she builds a pocket nest. Of course these last cases do not prove that there is not greater safety in a hidden nest, they only show that the color of the mother bird is not the main factor in the problem. But that a bird in a hole is safer than a bird in an open nest may well be doubted. The eggs are probably more secure from the thievish crow and the blue jay, but not from rats and squirrels and weasels. I know that the nests of the bluebird and the chickadee are often broken up by some small enemy.
We fancy that the birds are guided by their instinct for protective colors in the materials they choose for their nests. Most birds certainly aim to conceal their nests
the solitary builders, but not those that nest in communities, like the cliff swallows and rooks and flamingoes - and the materials they use favor this concealment. But what other materials could they use? They choose the material everywhere near at hand, moss, leaves, dry grass, twigs, mud, and the like. The ground-builders scrape together a few dry straws and spears of grass; the tree-builders, twigs and lichens and cotton and rootlets and other dry wood
products. There is nothing else for them to use. If a man builds a hut or a shanty in the fields or woods with such material as he finds ready at hand, his habitation will be protectively colored also. The winter wren builds its mouse-like nest of green moss, but in every case that has come under my observation the nest has been absolutely hidden by its position under a log or in a stump, or amid the roots of trees, and the most conspicuous colors would not have betrayed it to its enemies. In fact, the birds that build hidden nests in holes or tree cavities use of necessity the same neutral materials as those that build openly.
Birds that deliberately face the exterior of their nests with lichens obtained from rocks and trees, such as the hummingbird, the blue-gray gnatcatcher, and the wood pewee, can hardly do so with a view to protection, because the material of their nests is already weather-worn and inconspicuous. The lichens certainly give the nest an artistic finish and make it a part of the branch upon which it is placed, to an extent that suggests something like taste in the builders. But I fail to see how a marauding crow, or a jay, or a squirrel, or a weasel, or any other enemy of the bird could be cheated by this device.
I find myself less inclined to look upon the neutral grays and browns of the animal world as the result
of the struggle for existence, but more disposed to regard them as the result of the same law or tendency that makes nature in general adaptive and harmonious the outcome of the blendings, the
adjustments, the unifying processes or tendencies that are seen and felt all about us. Is not open-air nature ever striving toward a deeper harmony and unity? Do not differences, discrepancies, antagonisms, tend to disappear? Is there not everywhere something at work to bring about agreements, correspondences, adaptations? to tone down contrasts, to soften outlines, to modify the abrupt, to make peace between opposites? Is not the very condition of life and well-being involved in this principle? The abrupt, the disjoined, the irreconcilable, mean strife and dissolution; while agreements, gradations, easy transitions, mean life and growth. Like tends to beget like; the hand is subdued to the element it works in. The environment sets its stamp more or less strongly upon all living things. Even the pyramids are the color of the sands. Leave your bones there, and they will soon be of the same tint. Even your old boots or old coat will in time come to blend a little with the desert.
The tendency in nature that is over all and under all is the tendency or effort toward harmony to get rid of strife, discord, violent contrasts, and to adjust every creature to its environment. Inside of this great law or tendency are the lesser
laws of change, variety, opposition, contrast. Life must go on, and life for the moment breaks the unity, the balance. May not what is called protective coloration be largely this stamp of the environment, this tendency to oneness, to harmony and simplicity, that pervades nature, organic no less than inorganic?
Things in nature blend and harmonize; one thing matches with another. All open-air objects tend to take on the same color-tones; everything in the woods becomes woodsy, things upon the shore get the imprint of the shore, things in the water assume the hues of the water, the lichen matches the rock and the trees, the shell matches the beach and the waves; everywhere is the tendency to unity and simplicity, to low tones and adaptive colors.
One would not expect animals of the plains or of the desert to be colored like those of the bush or of the woods; the effects of the strong uniform light in the one case and of the broken and checkered light in the other would surely result in different coloration. That never-ending brown or gray or white should not in time stamp itself upon the creatures living in the midst of them is incredible.
Through the action of this principle, water animals will be water-colored, the fish in tropic seas will be more brilliantly colored than those in northern seas, tropical birds and insects will be of gayer
hues than those of the temperate zones, shore birds will be shore-tinted, Arctic life will blend more or less with Arctic snows, ground animals will assimilate to the ground colors, tree animals will show greater variety in tint and form, plains animals will be dull of hue like the plains - all this, as I fancy, not primarily for protection or concealment, but through the law of natural assimilation, like begetting like, variety breeding variety.
What more natural than that strictly wood birds should be of many colors and shades, to be in keeping with their surroundings? Will not the play of light and shade, the multiplicity of forms, and the ever moving leaves come in time to have their due effect? Will not a variety of influences tend to produce a variety of results? Will not sameness breed sameness? Would not one expect the hummingbirds to be more brilliant than the warblers, and the warblers more varied in color than the finches? the insect-feeders than the seed-eaters? The hummingbirds are, as it were, begotten by the flowers and the sunshine, as the albatross is begotten by the sea, and the whippoorwill by the dusk. The rat will not be as bright of tint as the squirrel, nor the rabbit as the fox.
In the spring one may sometimes see a bluebird, or a redbird, or a bright warbler for a moment upon the ground. How artificial and accidental it looks, like a piece of ribbon or a bit of millinery dropped