It is the nature of this bird (guillemot), as well as of most of those birds which habitually dive to take their prey, to perform all their evolutions under water with the aid of their wings; but instead of dashing at once into the midst of the terrified group of small prey, by which only a few would be captured, it passes round and round them, and so drives them into a heap; and thus has an opportunity of snatching here one and there another as it finds it convenient to swallow them; and if any one pushes out to escape, it falls the first prey of the devourer. The manner in which this bird removes the egg of a gull or hen to some secure place to be devoured, when compared with that in which a like conveyance is made by the parent for the safety of its future progeny, affords a striking manifestation of the difference between appetite and affection. When influenced by affection, the brittle treasure is removed without flaw or fracture, and is replaced with tender care; but the plunderer at once plunges his bill into its substance, and carries it off on its point.[161]
Speaking of the feeding habits of the lapwing, Jesse says:—
When the lapwing wants to procure food, it seeks for a worm's cast, and stamps the ground by the side of it with its feet. After doing this for a short time, the bird waits for the issue of the worm from its hole, which, alarmed at the shaking of the ground, endeavours to make its escape, when it is immediately seized, and becomes the prey of the ingenious bird. The lapwing also frequents the haunts of moles, which, when in pursuit of worms on which they feed, frighten them, and the worm, in attempting to escape, comes to the surface of the ground, when it is seized by the lapwing.[162]
Again,—
A lady of Dr. E. Darwin's acquaintance saw a little bird repeatedly hop on a poppy stem, and shake the head with his bill, till many seeds were scattered, when it settled on the ground and picked up the seeds.[163]
It is a matter of common remark that in countries where vultures abound, these birds rapidly 'gather together where the carcass is,' although before the death of their prey no bird was to be seen in the sky. The question has always been asked whether the vultures are guided to the carcass by their sense of smell or by that of sight; but this question is really no longer an open one. When Mr. Darwin was at Valparaiso he tried the following experiment. Having tied a number of condors in a long row, and having folded up a piece of meat in paper, he walked backwards and forwards in front of the row, carrying the meat at a distance of three yards from them, 'but no notice whatever was taken.' He then threw the meat upon the ground, within one yard of an old male bird; 'he looked at it for a moment with attention, but then regarded it no more.' With a stick he next pushed the meat right under the beak of the bird. Then for the first time the bird smelled it, and tore open the paper 'with fury, and at the same moment every bird in the long row began struggling and flapping its wings.'[164] Thus there can be no doubt that vultures do not depend on their sense of smell for finding carrion at a distance. Nor is it mysterious why they should find it by their sense of sight. If over an area of many square miles there are a number of vultures flying as they do at a very high elevation, and if one of the number perceives a carcass and begins to descend, the next adjacent vultures would see the descent of the first one, and follow him as a guide, while the next in the series would follow these in the same way, and so on.
Coming now to special instincts relating to incubation and the care of offspring, a correspondent writes:—
Last spring I had a pair of canaries, in an ordinary breeding cage (with two small boxes for nests in a compartment at one end). In due course the first egg was laid, which I inspected through the little door made for that purpose. The next day I looked again; still only one egg, and so for four or five days. It being evident, from the appearance of the hen, that there were more eggs coming, and as she seemed in good health, I supposed she might have broken some; and I took out the box, and examined it carefully for the shells (but without pulling the nest to pieces), and found nothing, until towards the beginning of another week I went to take the one egg away, as the hen seemed preparing to sit upon it. There were two eggs! The next morning, to my surprise, she was sitting upon six eggs! She must therefore have buried four of them in the four corners of the box, and so deep that I had been unable to find them. At first I thought that she had done so merely from dislike at their being looked at, but on reflection it has occurred to me that she did it that all might be hatched at the same time (as they subsequently were); for she was perfectly tame, and would almost suffer herself to be handled when on her nest. Wild birds never seem to conceal their eggs before sitting; but then (having more amusements than cage birds) they do not revisit their eggs after laying, until they have laid their number, whereas a caged bird, having nothing to divert her attention from her nest, often sits on it the greater part of the day.
I am not aware that this curious display of forethought on the part of a caged bird has been hitherto recorded, and seeing, as my correspondent points out, that it has reference to the changed conditions of life brought about by domestication, it may be said to constitute the first step in the development of a new instinct, which, if the conditions were of sufficiently long continuance, might lead to an important and permanent change of the ancestral instinct.
I have several interesting facts, also communicated to me by correspondents, similarly relating to individual variations of the ancestral instinct of incubation in order to meet the requirements of a novel environment. Thus Mr. J. F. Fisher tells me that while he was a commander in the East India trade he always took a quantity of fowls to sea for food. The laying-boxes being in a confined space, the hens used to quarrel over their occupancy; and one of the hens adopted the habit of removing the 'nest-eggs' which Mr. Fisher placed in one of the boxes to another box of the same kind not very far away. He watched the process through a chink of a door, and 'saw her curl her neck round the egg, thus forming a cup by which she lifted the egg,' and conveyed it to the other box. He adds:—