Those who affirm that wind-eggs are the residua of eggs previously begotten from copulation are mistaken in this assertion; for we have cases well authenticated where chickens of the common hen and goose have laid wind-eggs without ever having been subjected to copulation. Wind-eggs are smaller, less palatable, and more liquid than true eggs, and are produced in greater numbers. When they are [25] put under the mother bird, the liquid contents never coagulate, but both the yellow and the white remain as they were. Wind-eggs are laid by a number of birds: as for instance by the common hen, the partridge, the pigeon, the peahen, the goose, and the vulpanser. Eggs are hatched under brooding hens more rapidly in summer than in winter; that is to say, hens hatch in eighteen days in summer, but occasionally in [560a1] winter take as many as twenty-five. And for brooding purposes some birds make better mothers than others. If it thunders while a hen-bird is brooding, the eggs get addled. Wind-eggs that are called by some cynosura and uria are produced chiefly [5] in summer. Wind-eggs are called by some zephyr-eggs, because at spring-time hen-birds are observed to inhale the breezes; they do the same if they be stroked in a certain way by hand. Wind-eggs can turn into fertile eggs, and eggs due to previous [10] copulation can change kind, if before the change of the yellow to the white the hen that contains wind-eggs or eggs begotten of copulation be trodden by another cock-bird. Under these circumstances the wind-eggs turn into fertile eggs, and the previously impregnated eggs follow the breed of the impregnator; but if the latter [15] impregnation takes place during the change of the yellow to the white, then no change in the egg takes place: the wind-egg does not become a true egg, and the true egg does not take on the breed of the latter impregnator. If when the egg-substance is small copulation be intermitted, the previously existing egg-substance exhibits no increase; but if the hen be again submitted to the male the increase in size proceeds [20] with rapidity.
The yolk and the white are opposite not only in colour but also in properties. Thus, the yolk congeals under the influence of cold, whereas the white instead of congealing is inclined rather to liquefy. Again, the white stiffens under the influence of fire, whereas the yolk does not stiffen; but, unless it be burnt through, it [25] remains soft, and in point of fact is inclined to set or to harden more from the boiling than from the roasting of the egg. The yolk and the white are separated by a membrane from one another. The ‘hail-stones’ that are found at the extremity of the yellow in no way contribute towards generation, as some suppose: they are two in number, one below and the other above. If you take out of the shells a number of [560b1] yolks and a number of whites and pour them into a saucepan and boil them slowly over a low fire, the yolks will gather into the centre and the whites will set all round them.
Young hens lay first at the beginning of spring and lay more eggs than the [5] older hens; but the eggs of the younger hens are comparatively small. As a general rule, if hens get no brooding they pine and sicken. After copulation hens shiver and shake themselves, and often kick rubbish about all round them—and this they do [10] sometimes after laying—whereas pigeons trail their rumps on the ground, and geese dive under the water. Conception of the true egg and conformation of the wind-egg take place rapidly with most birds; as for instance with the hen-partridge when in heat. The fact is that, when she stands to windward and within scent of the male, [15] she conceives, and becomes useless for decoy purposes; for the partridge appears to have a very acute sense of smell.
The generation of the egg after copulation and the generation of the chick from the subsequent concoction of the egg are not brought about within equal periods for all birds, but differ according to the size of the parent-birds. The egg of the common [20] hen after copulation sets and matures in ten days as a general rule; the egg of the pigeon in a somewhat lesser period. Pigeons have the faculty of holding back the egg at the very moment of parturition; if a hen pigeon is put about by anyone, for instance if it be disturbed on its nest, or have a feather plucked out, or sustain any other annoyance or disturbance, then even though she was on the point of laying, she can keep the egg back in abeyance.
[25] A singular phenomenon is observed in pigeons with regard to pairing: that is, they kiss one another just when the male is on the point of mounting the female, and without this preliminary the male would decline to perform his function.1 With the older males the preliminary kiss is only given to begin with, and subsequently he mounts without previously kissing; with younger males the preliminary is never omitted. Another singularity in these birds is that the hens tread one another when a [30] cock is not forthcoming, after kissing just as the males do. Though they do not impregnate one another they lay more eggs under these than under ordinary circumstances; no chicks, however, result therefrom, but all such eggs are wind-eggs. [561a1]
3 · Generation from the egg proceeds in an identical manner with all birds, but the full periods from conception to birth differ, as has been said. With the [5] common hen after three days and three nights there is the first indication of the embryo; with larger birds the interval being longer, with smaller birds shorter. Meanwhile the yolk comes into being, rising towards the sharp end, where the primal element of the egg is situated, and where the egg gets hatched; and the heart [10] appears, like a speck of blood, in the white of the egg. This point beats and moves as though endowed with life, and from it, as it grows, two vein-ducts with blood in them trend in a convoluted course towards each of the two circumjacent integuments; and a membrane carrying bloody fibres now envelops the white, leading off [15] from the vein-ducts. A little afterwards the body is differentiated, at first very small and white. The head is clearly distinguished, and in it the eyes, swollen out to a great extent. This condition lasts on for a good while, as it is only by degrees that they diminish in size and contract. At the outset the under portion of the body [20] appears insignificant in comparison with the upper portion. Of the two ducts that lead from the heart, the one proceeds towards the circumjacent integument, and the other, like a navel-string, towards the yolk. The origin of the chick is in the white of the egg, and the nutriment comes through the navel-string out of the yolk. [25]
When the egg is now ten days old the chick and all its parts are distinctly visible. The head is still larger than the rest of its body, and the eyes larger than the head, but still devoid of vision. At this time the eyes become projecting, larger than beans, and black; if the cuticle be peeled off them there is a white and cold liquid [30] inside, quite glittering in the sunlight, but there is no hard substance whatsoever. Such is the condition of the head and eyes. At this time also the internal organs are [561b1] visible, as also the stomach and the arrangement of the viscera; and the veins that seem to proceed from the heart are now close to the navel. From the navel there [5] stretch a pair of veins; one towards the membrane that envelops the yolk (and the yolk is now liquid, or more bulky than is normal), and the other towards that membrane which envelops collectively the membrane wherein the chick lies, the membrane of the yolk, and the intervening liquid. [For, as the chick grows, little by [10] little one part of the yolk goes upward, and another part downward, and the white liquid is between them; and the white of the egg is underneath the lower part of the yolk, as it was at the outset. On the tenth day the white is at the extreme outer surface, reduced in amount, glutinous, firm in substance, and sallow in colour.]2
The disposition of the several constituent parts is as follows. First and [15] outermost, next to the shell, comes the membrane of the egg, not that of the shell, but underneath it. Inside this membrane is a white liquid; then comes the chick, and a membrane round about it, separating it off so as to keep the chick free from the [20] liquid; next after the chick comes the yolk [into which one of the two veins was described as leading, the other one leading into the enveloping white substance. A membrane with a liquid resembling serum envelops the entire structure. Then comes another membrane right round the embryo, as has been described, separating it from the liquid. Underneath this comes the yolk, enveloped
in another [25] membrane (into which yolk proceeds the navel-string that leads from the heart and the big vein), so as to keep the embryo free of both liquids.]3
About the twentieth day, if you open the egg and touch the chick, it moves inside and chirps; and it is already coming to be covered with down, when, after the twentieth day is past, the chick begins to break the shell. The head is situated over [30] the right leg close to the flank, and the wing is placed over the head; and about this time is plain to be seen the membrane resembling an after-birth that comes next after the outermost membrane of the shell, into which membrane the one of the [562a1] navel-strings was described as leading (and the chick in its entirety is now within it), and so also is the other membrane resembling an after-birth, namely that surrounding the yolk, into which the second navel-string was described as leading; and both of them were described as being connected with the heart and the big vein. [5] At this time the navel-string that leads to the outer after-birth collapses and becomes detached from the chick, and the membrane that leads into the yolk is fastened on to the thin gut of the creature, and by this time a considerable amount of the yolk is inside the chick and a yellow sediment is in its stomach. About this [10] time it discharges residuum in the direction of the outer after-birth, and has residuum inside its stomach; and the outer residuum is white and there comes a white substance inside. By and by the yolk, diminishing gradually in size, at length becomes entirely used up and comprehended within the chick (so that, ten days [15] after hatching, if you cut open the chick, a small remnant of the yolk is still left in connexion with the gut), but it is detached from the navel, and there is nothing in the interval between, but it has been used up entirely. During the period above referred to the chick sleeps, but if it is moved it wakes, looks up and chirps; and the [20] heart and the navel together palpitate as though the creature were respiring. So much as to generation from the egg in the case of birds.
Birds lay some eggs that are unfruitful, even eggs that are the result of copulation, and no life comes from such eggs by incubation; and this phenomenon is observed especially with pigeons.
[25] Twin eggs have two yolks. In some twin eggs a thin partition of white intervenes to prevent the yolks mixing with each other, but some twin eggs are unprovided with such partition, and the yolks run into one another. There are some hens that lay nothing but twin eggs, and in their case the phenomenon regarding the [30] yolks has been observed. For instance, a hen has been known to lay eighteen eggs, and hatch twins out of them all, except those that were wind-eggs; the rest were [562b1] fertile (though one of the twins is always bigger than the other), but the eighteenth was monstrous.
4 · Birds of the pigeon kind, such as the ring-dove and the turtle-dove, lay two eggs at a time as a general rule, and they never lay more than three. The pigeon, as has been said, lays at all seasons; the ring-dove and the turtle-dove lay in the [5] spring-time, and they never lay more than twice in the same season. The hen-bird lays the second pair of eggs when the first pair happens to have been destroyed, for many of the hen-pigeons destroy the first brood. The hen-pigeon, as has been said, occasionally lays three eggs, but it never rears more than two chicks, and sometimes rears only one; and the odd one is always a wind-egg. [10]
Very few birds propagate within their first year. All birds, after once they have begun laying, keep on having eggs, though in the case of some birds it is difficult to detect the fact from the minute size of the creature.
The pigeon, as a rule, lays a male and a female egg, and generally lays the male [15] egg first; after laying she allows a day’s interval to ensue and then lays the second egg. The male takes its turn of sitting during the daytime; the female sits during the night. The first-laid egg is hatched and brought to birth within twenty days; and the mother bird pecks a hole in the egg the day before she hatches it out. The two parent [20] birds brood for some time over the chicks in the way in which they brooded previously over the eggs. In all connected with the rearing of the young the female parent is more cross-tempered than the male, as is the case with most animals after parturition. The hens lay as many as ten times in the year; occasional instances have [25] been known of their laying eleven times, and in Egypt they actually lay twelve times. The pigeon, male and female, couples within the year; in fact, it couples when only six months old. Some assert that ring-doves and turtle-doves pair and procreate when only three months old, and instance their superabundant numbers by way of [30] proof of the assertion. The hen-pigeon carries her eggs fourteen days; for as many more days the parent birds hatch the eggs; by the end of another fourteen days the chicks are so far capable of flight as to be overtaken with difficulty. [The ring-dove, [563a1] they say, lives up to forty years. The partridge lives over sixteen. After one brood the pigeon is ready for another within thirty days.]4
5 · The vulture builds its nest on inaccessible cliffs; for which reason its nest [5] and young are rarely seen. And therefore Herodorus, father of Bryson the Sophist, declares that vultures come from some foreign country unknown to us, stating as a proof of the assertion that no one has ever seen a vulture’s nest, and also that vultures in great numbers make a sudden appearance in the rear of armies. [10] However, difficult as it is to get a sight of it, a vulture’s nest has been seen. The vulture lays two eggs.
Carnivorous birds in general have not been observed to lay more than once a year. The swallow is the only carnivorous bird that builds a nest twice. If you prick out the eyes of swallow chicks while they are yet young, the birds will get well again [15] and will see by and by.
6 · The eagle lays three eggs and hatches two of them, as it is said in the verses ascribed to Musaeus:
That lays three, hatches two, and cares for one.
[20] This is the case in most instances, though a brood of three has been observed. As the young ones grow, the mother becomes wearied with feeding them and extrudes one of the pair from the nest. [At the same time the bird is said to abstain from food, to avoid harrying the young of wild animals. Thus its wings blanch, and for some days [25] its talons get turned awry. It is in consequence about this time cross-tempered to its own young.]5 The phene is said to rear the young one that has been expelled from the nest. The eagle broods for about thirty days.
The hatching period is about the same for the larger birds, such as the goose and the great bustard; for the middle-sized birds it extends over about twenty days, [30] as in the case of the kite and the hawk. The kite in general lays two eggs, but occasionally rears three young ones. The so-called aegolius at times rears four. It is [563b1] not true that, as some aver, the raven lays only two eggs; it lays a larger number. It broods for about twenty days and then extrudes its young. Other birds perform the same operation; at all events mother birds that lay several eggs often extrude one of their young.
[5] Birds of the eagle species are not alike in the treatment of their young. The white-tailed eagle is cross, the black eagle is affectionate in the feeding of the young; though, all birds of prey, as soon as their brood is able to fly, beat and extrude them from the nest. The majority of birds other than birds of prey, as has [10] been said, also act in this manner, and after feeding their young take no further care of them; but the crow is an exception. This bird for a considerable time takes charge of her young; for, even when her young can fly, she flies alongside of them and supplies them with food.
7 · The cuckoo is said by some to be a hawk transformed, because the hawk [15] disappears at that time. It is like . . .6 And the other hawks too are hardly to be seen once the cuckoo has begun to call, except for a few days. The cuckoo appears only for a short time in summer, and in winter disappears. The hawk has crooked talons, [20] which the cuckoo has not; neither with regard to the head does the cuckoo resemble the hawk. In point of fact, both as regards the head and the claws it more resembles the pigeon. However, in colour and in colour alone it does resemble the hawk, only that the markings of the hawk are striped, and of the cuckoo mottled. And in size [25] and flight
it resembles the smallest of the hawk tribe, which bird disappears as a rule about the time of the appearance of the cuckoo, though the two have been seen simultaneously. The cuckoo has been seen to be preyed on by the hawk; and this never happens between birds of the same species. They say no one has ever seen the [30] young of the cuckoo. The bird lays eggs, but does not build a nest. Sometimes it lays its eggs in the nest of a smaller bird after first devouring the eggs of this bird; it lays by preference in the nest of the ring-dove, after first devouring the eggs of the [564a1] pigeon. (It occasionally lays two, but usually one.) It lays also in the nest of the hypolais, and the hypolais hatches and rears the brood. It is about this time that the bird becomes fat and palatable. The young of hawks also get palatable and fat. One species builds a nest in the wilderness and on sheer cliffs. [5]
8 · With most birds, as has been said of the pigeon, the hatching is carried on by the male and the female in turns: with some birds, however, the male only sits long enough to allow the female to provide herself with food. In the goose tribe the female alone incubates, and after once sitting on the eggs she continues brooding [10] until they are hatched.
The nests of all marsh-birds are built in swampy districts well supplied with grass; consequently, the motherbird while sitting quiet on her eggs can provide herself with food without having to submit to absolute fasting. [15]
The Complete Works of Aristotle Page 154