It will be at once evident that in the above account of the habits of the Cuckoo there is a great deal of truth, although much that is surmised is devoid of foundation. The main facts that have been established by trustworthy observation relative to the breeding of the Cuckoo are in themselves sufficiently curious, and have no need of fictitious circumstances to make them interesting. They may be briefly stated as follows:--The female Cuckoo undoubtedly deposits her eggs in the nest of some other bird, not of any particular species, but of several; indeed, upwards of fifty have been enumerated as entitled to the honour of rearing the young Cuckoos. Secondly, it has been observed that the eggs of the Cuckoo differ remarkably from each other; indeed, more so than is the case in any other known species; and, moreover, that a Cuckoo's egg taken from the nest in which it has been placed is found strikingly to resemble the eggs laid by the owner of the nest. Thirdly, the Cuckoo only lays a single egg in the selected spot, and this is invariably deposited in a nest already containing eggs belonging to its proper owner. The behaviour of the females while thus employed in laying their eggs is peculiar. No sooner do these birds arrive in the early spring than the males begin to make the woods resound with their well-known call, where they are soon joined by their mates, of whose coyness under the circumstances they can have little cause for complaint, and as soon as the female has an egg ready for laying, away she flies in search of a nest in which to deposit her burden. On these expeditions she is not accompanied by the male Cuckoo, with whose company, indeed, she seems by no means desirous of being troubled. Her search after a suitable nest is always made on the wing, and her cleverness in finding the object of her journey, however well it may seem to be hidden from observation, is at least remarkable. Quite contrary to her usual shyness, at such times she will unhesitatingly approach quite close to human habitations, and even enter buildings, such as barns and outhouses. If the shape and situation of the discovered nest is such as to allow her to do so, she places herself upon it and lays an egg, but if such is not the case she lays her egg upon the ground, and then taking it in her beak drops it into the nest. Sometimes it happens that she has considerable difficulty in introducing her egg into the nest, owing to the smallness of the aperture, and occasionally the bird has been captured during her endeavours to overcome the difficulty. Sometimes it has happened that two Cuckoos' eggs, of different colours, have been found in the same nest. [Illustration: THE CUCKOO (_Cuculus canorus_).]