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Originally appearing in Volume V07, Page 610 of the 1911 Encyclopedia Britannica.
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YIL 20of such a species there would be no need 41 anvtbing further to ensure success—the terror of the nest-owner ae .,eeing her home invaded by a hawk-like giant, and some of her treasures tossed out, would be enough to stir her motherly feelings so deeply that she would without misgiving, if not with joy that something had been spared to her, resume the duty of incubation so soon as the danger was past. But with other species it may be, and doubtless is, different. Here assimilation of the introduced egg to those of the rightful owner may be necessary, for there can hardly be a doubt as to the truth of Dr Baldamus's theory as to the object of the assimilation being to render the cuckoo's egg "less easily recognized by the foster-parents as a substituted one." It is especially desirable to point out that there is not the slightest ground for imagining that the cuckoo, or any other bird, can voluntarily influence the colour of the egg she is about to lay. Over that she can have no control, but its destination she can determine. It would seem also impossible that a cuckoo, having laid an egg, should look at it, and then decide from its appearance in what bird's nest she should put it. That the colour of an egg-shell can be in some mysterious way affected by the action of external objects on the perceptive faculties of the mother is a notion too wild to be seriously entertained. Consequently, only one explanation of the facts can here be suggested. Every one who has sufficiently studied the habits of animals will admit the influence of heredity. That there is a reasonable probability of each cuckoo most commonly putting her eggs in the nest of the same species of bird, and of this habit being transmitted to her posterity, does not seem to be a very violent supposition. Without attributing any wonderful sagacity to her, it does not seem unlikely that the cuckoo which had once successfully foisted her egg on a reed-wren or a titlark should again seek for another reed-wren's or another titlark's nest (as the case may be), when she had another egg to dispose of, and that she should continue her practice from one season to another. It stands on record (Zoologist, 1873, p. 3648) that a pair of wag-tails built their nest for eight or nine years running in almost exactly the same spot, and that in each of those years they fostered a young cuckoo, while many other cases of like kind, though not perhaps established on so good authority, are believed to have happened. Such a habit could hardly fail to become hereditary, so that the daughter of a cuckoo which always put her egg into a reed-wren's, titlark's or wagtail's nest would do as did her mother. Furthermore it is unquestionable that, whatever variation there may be among the eggs laid by different individuals of the same species, there is a strong family likeness between the eggs laid by the same individual, even at the interval of many years, and it can hardly be questioned that the eggs of the daughter would more or less resemble those of her mother. Hence the supposition may be fairly credited that the habit of laying a particular style of egg is also likely to become hereditary. Combining this supposition with that as to the cuckoo's habit of using the nest of the same species becoming hereditary, it will be seen that it requires only an application of the principle of natural selection to show the probability of this principle operating in the course of time to produce the facts asserted by the anonymous Solognot of the 18th century, and by Dr Baldamus and others since. The particular gens of cuckoo which inherited and transmitted the habit of depositing in the nest of any particular species of bird eggs having more or less resemblance to the eggs of that species would prosper most in those members of the gens where the likeness was strongest, and the other members would (ceteris paribus) in time be eliminated. As already shown, it is not to be supposed that all species, or even all individuals of a. species, are duped with equal ease. The operation of this kind of natural selection would be most needed in those cases where the species are not easily duped—that is, in those cases which occur the least frequently. Here it is we find it, for observation shows that eggs of the cuckoo deposited in nests of the red-backed shrike (Lanius collurio), of the bunting (Emberiza miliaria), and of the icterine warbler approximate in their colouring to eggs of those species—species in whose nests the cuckoo rarely (in comparison with others) deposits eggs. S2 Of species which are more easily duped, such as the hedge-sparrow, mention has already been made. More or less nearly allied to the British cuckoo are many other forms of the genus from various parts of Africa, Asia and their islands, while one even reaches Australia. In some cases the chief difference is said to lie in the diversity of voice—a character only to be appreciated by those acquainted with the living birds, and though of course some regard should be paid to this distinction, the possibility of birds using different "dialects" according to the locality they inhabit must make it a slender specific diagnostic. All these forms are believed to have essentially the same habits as the British cuckoo, and, as regards parasitism the same is to be said of the large cuckoo of southern Europe and North Africa (Cbccystes glandarius), which victimizes pies (Pica mauritanica and Cyanopica cooki) and crows (Corvus cornix). True it is that an instance of this species, commonly known as the great spotted cuckoo, having built a nest and hatched its young, is on record, but the later observations of others tend to cast doubt on the credibility of the ancient report. It is worthy of remark that the eggs of this bird so closely resemble those of one of the pies in whose' nest they have been found, that even expert zoologists have been deceived by them, only to discover the truth when the cuckoo's embryo had been extracted from the supposed pie's egg. This species of cuckoo, easily distinguishable by its large size and long crest, has more than once made its appearance as a straggler in the British Isles. Equally parasitic are many other cuckoos, belonging chiefly to genera which have been more or less clearly defined as Cacomantis, Chrysococcyx, Eudynamis, Oxylophus, Poly phasia and Surniculus, and inhabiting parts of the Ethiopian, Indian and Australian regions ;1 but there are certain aberrant forms of Old World cuckoos which unquestionably do not shirk parental responsibilities. Among these especially are the birds placed in or allied to the genera Centro pus and Coua—the former having a wide distribution from Egypt to New South Wales, living much on the ground and commonly called lark-heeled cuckoos; the latter bearing no English name, and limited to the island of Madagascar. These build a nest, not perhaps in a highly finished style of architecture, but one that serves its end. Respecting the cuckoos of America, the evidence; though it has been impugned, is certainly enough to clear them from the charge which attaches to so many of their brethren of the Old World. There are two species very well known in parts of the United States and some of the West Indian Islands (Coccyzus ,tmericanus and C. erythrophthalmus), and each of them has occasionally visited Europe. They both build nests—remarkably small structures when compared with those of other birds of their size—and faithfully incubate their delicate sea-green eggs. In the south-western states of the Union and thence into Central America is found another curious form of cuckoo (Geococcyx)—the chaparral-cock of northern and paisano of southern settlers. The first of these names it takes from the low brushwood (chaparral) in which it chiefly dwells, and the second is said to be due to its pheasant-like (faisan corrupted into paisano, properly a countryman) appearance as it runs on the ground. Indeed, one of the two species of the genus was formerly described as a Phasianus. They both have short wings, and seem never to fly, but run with great rapidity. Returning to arboreal forms, the genera Neomorphus, Diplopterus, Saurothera and Piaya (the last two commonly called rain-birds, from the belief that their cry portends rain). may be noticed—all of them belonging to the Neotropical region; but perhaps the most curious form of American cuckoos is the ani (Crotophaga), of which three species ,inhabit the same region. The best-known species (C. ani) is fond throughout the Antilles and on the opposite continent. In most of the British colonies it is known as the black witch, and is accused of various malpractices—it being, in truth, a perfectly harmless if not a beneficial bird. As regards its propagation this aberrant form of cuckoo departs in one direction Evidence tends to show that the same is to be said of the curious channel-bill (Scythrops novae-hollandiae), though absolute proof seems to be wanting.from the normal habit of birds, for several females,' unite to lay their eggs in one nest. ' It is evident that incubation is carried on socially, since an intruder on approaching the rude nest will disturb perhaps half a dozen of its sable proprietors, who, loudly complaining, seek safety either in the leafy branches of the tree that holds it, or in the nearest available covert. with all the speed that their feeble powers of flight permit. (A. N.) CUCKOO-SPIT, a frothy secretion found upon plants, and produced by the immature nymphal stage of various plant-lice of the familiar Cercopidae and Jassidae, belonging to the homopterous division of the Hemiptera, which in the adult condition are sometimes called frog-hoppers.
End of Article: YIL
YNVOLUTION (Lat. involvere, to roll up)

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