IT is probable that no bird has excited more general interest among all peoples and in all ages than the common cuckoo,—so-called to distinguish our familiar European species from others of its family. Folk-tales and stories, poetry and superstition, in all tongues testify unmistakably to the hold that it has taken on the popular imagination; nor is this to be wondered at when its remarkable life-story is considered. The musical and distinctive call-note which heralds its arrival at its breeding stations coincides with the long looked-for approach of summer, and has given to it its name in the language of practically every country which it visits. In German Kukuk, French coucou, Dutch koekoek, Gaelic cubhag or cu’ag, Latin cuculus, Greek KOKKUE, Sanskrit koka; these are only some of the instances that might be mentioned. Our Scottish name of gowk may possibly be derived from the Gaelic, but is also evidently near akin to the German `Gauch,' a popular alternative to `Kukuk.'

As may be gathered from this incomplete list of names, the cuckoo is very widely distributed, extending in its European range to the Arctic circle, and in Asia as far east as Japan. It is common in some parts of India, is recorded from Arabia, Egypt and Nubia, and is said to penetrate as far as South Africa.

With us in Scotland, the cuckoo is to be looked for in ordinary seasons towards the end of April. The earliest date in a series extending over a considerable number of years in the West of Scotland was the 21st April (1898), and the latest the 8th May (1906 and 1910). Such dates, however, are merely approximate, as being those on which the bird was first heard-not seen. They may well have been with us for days previously, as uncongenial weather or scanty food supplies would keep them silent.

The cuckoo is a retiring bird, and is much more frequently heard than seen, especially the male, whose is the well-known call-note. When uttering this he is generally sitting concealed in thick foliage, and in doing so he drops his wings, raising the tail and bowing his head; but he also sometimes calls in flight, especially when pursuing the female.

When flying, the cuckoo strongly resembles our smaller birds of prey. The slate-coloured upper parts with the strongly barred light-coloured lower parts, the long wings and tail and well-feathered legs of the bird in its more ordinary plumage, are markedly suggestive of the sparrow-hawk. The younger females, however, are often very differently coloured, the slate and ash colour being replaced by a more or less rufous brown, and this again gives them a striking resemblance to the kestrel. This rufous plumage frequently persists even after the first and subsequent moults, so that earlier observers were inclined to suspect a specific difference, and named it C. hepaticacs; but further investigation proved this to be erroneous. This resemblance to our lesser birds of prey appears to be sufficient to deceive the little birds of various sorts that may often be seen following and mobbing the cuckoo, as if taking it for one of their natural enemies.

The male cuckoo, on arrival at its chosen summer quarters, selects for himself a certain locality or district, which it defends strenuously against all comers of his own sex. The females, which are said to be proportionately much fewer in number, move through wider bounds, making their presence known by their peculiar call-note, a chattering or laughing sound of invitation; it must be admitted that they practise polyandry. As all know, it builds no nest, but is a parasite pure and simple, foisting all the natural duties and labours of a parent on to the shoulders of its innocent little neighbours, and this, too, at the expense of their own broods ; for it must be remembered that for every young cuckoo raised to maturity a whole family of its foster-brethren are doomed to destruction.

The foster-parents selected by the female cuckoo belong, as a rule, to the various smaller insect-eating birds, such as the tit-lark, hedge-sparrow, redbreast, the wagtails, warblers and the like, the tit-lark or meadow-pipit being with us probably the most frequent victim. It is evident that the nest must be found and noted by the female cuckoo beforehand; and it must be owing to default in this respect that now and again the egg of the cuckoo is found in most unlikely and unsuitable nests, as, for instance, those of the stock dove, jay, and even of the little grebe. Such can only have been made use of in the last extremity. When the nest selected is sufficiently open and large, the egg is laid in the usual way ; but in the case, frequently occurring, when the nest is domed or covered, the egg is laid on the ground and then taken up by the mother in its beak and placed in the nest. The egg is remarkably small for the size of the bird, no bigger than a sparrow's, although the parent is much more than twice as large. They vary a good deal in colour, are mostly of a greyish ground, slightly blotched or speckled with darker shades. Dresser, who, in his Birds of Europe, has brought together the observations and theories of all the best authorities both of this country and of the Continent, describes a fine collection of eggs, many of which were blue, some uniform, some spotted.

A theory has been advanced that the cuckoo seeks a nest, the eggs of which resemble those which she herself lays. Newton appears to have held that it is a case of heredity, - that the cuckoo seeks for a nest of the same species as that in which it had itself been hatched. Dresser, however, makes the shrewd comment that such heredity could not well depend on the female alone, but also on the male, or, in the case of the cuckoo, probably on several males. The latter authority indeed rather disposes of the whole contention by his statement that in his own large collection of cuckoo's eggs less than a sixth of them resemble those of the foster-parent.

It was formerly held that the cuckoo contented itself with depositing its egg, and took no further part in the matter. It is now alleged that, if the nest already contains eggs, she will throw out some or all of them, and has even been known to devour them. This latter statement is denied by some, but Dresser quotes Sachse as an eyewitness to the fact. The period of incubation is the same as that of most of the foster parents, and it is stated by some writers that the cuckoo, drawn by an extraordinary instinct, returns to the nest exactly at the time of hatching, throwing out of the nest all young birds and eggs other than her own that she finds therein. Whether this is or is not sometimes the case. it is certainly not universal; for often, as all know, some of the brood remain, the last act of the tragedy being carried out by the young cuckoo itself. Growing with extraordinary quickness, it is already, after two days, much larger and stronger than its unfortunate foster-brethren. With restless and untiring energy it wriggles itself backward under its neighbour until it has got it perched in a peculiar shovel-like hollow in its back, and then, with great exertion, raises it to the edge of the nest and topples it over ; nor does it rest until it is the sole inhabitant of the structure. This action of the young cuckoo seems to have been first recorded by the famous Dr. Jenner, who, according to Yarrell, was asked to investigate the subject by John Hunter, and published the result in the Transactions of the Royal Society for 1788.

The food of the cuckoo consists of insects of all sorts, and largely of caterpillars, grubs and the like. It seems to be especially fond of the hairy caterpillars sometimes called 'woolly bears,' the gizzard having been found covered with these hairs adhering to it by their points. It must, therefore, be considered to be a useful species, although it doubtless causes many broods of our little birds to come to naught.

It is a puzzling and probably an unanswerable question as to the `reason why' of this strange habit of the cuckoo. It is known to lay its eggs only at an interval of several days, and some hold that this may explain the necessity of the parasitical habit, as it would be a matter of weeks before all the clutch were laid and ready for incubation; but this is also the case with some of the owls, where one finds a half-fledged nestling, an egg ready to hatch and one new laid all in the same nest, and yet they have no difficulty in carrying out the ordinary duties of incubation and rearing of their brood. Such is also the case with the American yellow-billed cuckoo, which builds its own nest and rears its own young; yet Yarrell states, on the authority of Audubon, that this bird also lays its eggs at considerable intervals, so that eggs and young at different stages of development are found together. Like our own species it is a migrant, and Pennant tells us that it arrives in New York in May, makes its nest in June, and retires from North America in autumn.

In summing up the evidence, there does not appear to be good ground for the theory that the cuckoo seeks intentionally the nests of species whose eggs resemble her own; one of the best German observers, A. Walters, having compared no less than 214 cuckoo's eggs with those of their foster-parents, with the result that in only some six cases was there a strong resemblance, while the great number bore no resemblance whatever. As to whether the mother cuckoo returns to the nest at hatching time to turn out the eggs of the foster-parents, the evidence seems in favour of the view that sometimes, at least, she does so ; while on the question of her devouring such eggs, Sachse has proved that such has occurred, although the cases may be, and probably are, exceptional.

It is interesting to note that the parasitical methods of the European cuckoo are not unique, but are reproduced in almost every feature in the case of a small American bird, the cow-bunting, cow-bird or cow-pen bird. Wilson, in his American Ornithology, gives a long and interesting account of this bird. Like our cuckoos they do not pair, nor do they build any nest, but deposit their eggs in the nests of other birds, just as does our cuckoo, and never more than one in each nest. If Wilson is correct, the cow-bird's egg hatches in a shorter time than those of the selected foster-parents, and shortly after it is hatched, the eggs of the original owners all disappear. Here the resemblance to the cuckoo story ceases, for with the removal of the eggs the young cow-bird has nothing to do. Nor is there any evidence that the cow-bird parent ever revisits the nest. Wilson appears to acquiesce in the opinion of Dr. Potter of Baltimore, that the only possible explanation is that the surplus eggs are removed by the foster-parents themselves.