Thus, on the whole, we may accept Dr. Davey's opinion—who had good opportunities for observation—that the snake-charmers control the cobras by working upon the well-known timidity and reluctance of these animals to use their fangs till they become virtually tame.
CHAPTER X.
BIRDS.
Adequately to treat of the intelligence of birds a separate volume would be required; here it must be enough to deal with this class as I shall afterwards deal with the Mammalia—namely, by giving an outline sketch of the more prominent features of their psychology.
Memory.
The memory of birds is well developed. Thus, although we are much in the dark on the whole subject of migration—so much so that I reserve its discussion with all the problems that this presents for a separate chapter in my next work—we may at least conclude that the return of the same pair of swallows every year to the same nest must be due to the animals remembering the precise locality of their nests. Again, Buckland gives an account of a pigeon which remembered the voice of its mistress after an absence of eighteen months;[145] but I have not been able to meet with satisfactory evidence of the memory of a bird enduring for a longer time than this.
As it is a matter of interest in comparative psychology to trace as far as possible into detail the similarities of a mental faculty as it occurs in different groups of animals, and as the faculty of memory first admits of detailed study in the class which we are now considering, I shall here devote a paragraph to the facts concerning the exhibition of memory by birds where its mechanism best admits of being analysed; I refer to the learning of articulate phrases and tunes by talking and musical birds. The best observations in this connection with which I am acquainted are those of Dr. Samuel Wilks, F.R.S., and therefore I shall quote in extenso the portion of his paper which refers to the memory of parrots: other portions of this paper I shall have occasion to quote in my next work:—
When my parrot first came into my possession, several years ago, it was quite unlettered, and I therefore had an opportunity of observing the mode in which it acquired the accomplishment of speech. I was very much struck with its manner of learning, and the causes for its speaking on special occasions. The first seemed to resemble very much the method of children in learning their lessons, and the second to be due to some association or suggestion—the usual provocative for set speeches at all periods of human life. A parrot is well known to imitate sounds in a most perfect manner, even to the tone of the voice, besides having a compass which no human being can approach, ranging from the gravest to the most acute note. My bird, though possessing a good vocabulary of words and sentences, can only retain them for a few months unless kept constantly in practice by the suggestive recurrence of some circumstance which causes their continual utterance. If forgotten, however, they are soon revived in the memory by again repeating them a few times, and much more speedily than any new sentence can be acquired. In beginning to teach the parrot a sentence, it has to be repeated many times, the bird all the while listening most attentively by turning the opening of the ear as close as possible to the speaker. After a few hours it is heard attempting to say the phrase, or, I should say, trying to learn it. It evidently has the phrase somewhere in store, for eventually this is uttered perfectly, but at first the attempts are very poor and ludicrous. If the sentence be composed of a few words, the first two or three are said over and over again, and then another and another word added, until the sentence is complete, the pronunciation at first being very imperfect, and then becoming gradually more complete, until the task is accomplished. Thus hour after hour will the bird be indefatigably working at the sentence, and not until some days have elapsed will it be perfect. The mode of acquiring it seems to me exactly what I have observed in a child learning a French phrase; two or three words are constantly repeated, and then others added, until the whole is known, the pronunciation becoming more perfect as the repetition goes on. I found also on whistling a popular air to my parrot that she picked it up in the same way, taking note by note until the whole twenty-five notes were complete. Then the mode of forgetting, or the way in which phrases and airs pass from its recollection, may be worth remarking. The last words or notes are first forgotten, so that soon the sentence remains unfinished or the air only half whistled through. The first words are the best fixed in the memory; these suggest others which stand next to them, and so on till the last, which have the least hold on the brain. These, however, as I have before mentioned, can be easily revived on repetition. This is also a very usual process in the human subject: for example, an Englishman speaking French will, in his own country, if no opportunity occur for conversation, apparently forget it; he no sooner, however, crosses the Channel and hears the language than it very soon comes back to him again. In trying to recall poems learned in childhood or in school days, although at that period hundreds of lines may have been known, it is found that in manhood we remember only the two or three first lines of the 'Iliad,' the 'Æneid,' or the 'Paradise Lost.'[146]