From Birds Worth Knowing, published by Doubleday in 1931:
The Passenger Pigeon
Length – 16 to 26 inches.
Male – Upper parts bluish slate shaded with olive gray on back and shoulders, and with metallic violet, gold, and greenish reflections on back and sides of head; the wing coverts with velvety black spots; throat bluish slate, quickly shading into a rich reddish buff on breast, and paling into white underneath; two middle tail feathers blackish; others fading from pearl to white. Eyes red, like the feet; bill black.
Female – Similar, but upper parts washed with more olive brown; less iridescence; breast pale grayish brown fading to white underneath.
Range – Eastern North America, nesting chiefly north of or along the northern borders of the United States as far west as the Dakotas or Manitoba, and north to Hudsons Bay.
Season – Chiefly a transient visitor to the United States of late years.
The wild pigeon no longer survives to refute the adage, “In union there is strength.” No birds have shown greater gregariousness, the flocks once numbering not hundreds nor thousands but millions of birds; Wilson in 1808 mentioning a flock seen by him near Frankfort, Kentucky, which he conservatively estimated at more than two billion, and Audubon told of flights so dense that they darkened the sky, and streamed across it like mighty rivers. So late our Centennial year one nesting ground in Michigan extended over an area twenty-eight miles in length by three or four in width. The modern mind, accustomed to deal only with pitiful remnants of feathered races, can scarcely grasp the vast numbers that once made our land the sportsman’s paradise. Union for once has been fatal. Unlimited netting, even during the entire nesting season, has resulted in sending more than one million pigeons to market from a single roost in one year, leaving perhaps as many more wounded birds and starving, helpless, naked squabs behind, until the poultry stalls became so gutted with pigeons that the low price per barrel scarcely paid for their transportation, and they were fed to the hogs. This abominable practice of netting pigeons, discontinued only because there were no flocks left to capture, drove the birds either to nest north of the United States, or, when within its borders, to change their habits and live in couples chiefly. Captain Bendire, than whom no writer ever expressed an opinion out of fuller knowledge, said in 1892: “The extermination of the passenger pigeon has progressed so rapidly during the last twenty years that it looks now as if their (sic) total extermination might be accomplished within the present century.” This prophecy has been only too well fulfilled. The passenger pigeon is to-day as extinct as the great auk.
One or at most two white eggs, laid on a rickety platform of sticks in a tree, where they were visible from below, would scarcely account for the myriads of pigeons once seen, were not frequent nestings common throughout the summer; and it is said that birds laid again on their return South. Both of the devoted mates took regular turns at incubating, the female between two o’clock in the afternoon and nine or ten the next morning, daily, leaving the male only four or five hours sitting, according to Mr. William Brewster. “The males feed twice each day,” he says, “namely from daylight to about eight A.M., and again late in the afternoon. The females feed only in the forenoon. The change is made with great regularity as to time, all the males being on the nest by ten o’clock A.M… . The sitting bird does not leave the nest until after the bill of its incoming mate nearly touches its tail, the former slipping off as the latter takes its place … Five weeks are consumed by a single nesting … Usually the male pushes the young off the nest by force. The latter struggles and squeals precisely like a tame squab, but is finally crowded out along the branch, and after further feeble resistance flutters down to the ground. Three or four days elapse before it is able to fly well. Upon leaving the nest it is often fatter and heavier than the old birds; but it quickly becomes thinner and lighter, despite the enormous quantity of food it consumes.” Before leaving the nest it was nourished with food brought up from its parents’ crops, where, mixed with a peculiar whitish fluid, it passed among the credulous as “pigeon’s milk.” Is not this the nearest approach among birds to the mammals’ method of feeding their young? Patterns of all domestic virtues, proverbially loving, gentle birds, anatomists tell us that their blandness was due not to the cultivation of their moral nature, but to the absence of the gall-bladder!