2. The eagle incubates for thirty days; this is the usual period of incubation for large birds, as the goose and the bustard. Moderately sized birds usually sit twenty days, as the ictinus[199] and hierax.[200] The ictinus usually produces two young ones, and sometimes three; the Ætolian kite, as it is called, sometimes produces four. The raven produces not only two, but, as they say, many eggs, which she sits upon for about twenty days. She also turns out some of her young ones. Many other birds do the same thing; and generally those which produce several turn out one. [199] Kite. [200] Hawk. 3. All kinds of eagles do not behave in the same way to their young; but the pygargus is cruel; and the black eagles are careful for the food of their young; but all birds with crooked talons as soon as their young can fly well beat them and drive them from the nest. And most birds of other classes, as I have before observed, do the same thing; and when they have brought them up, they take no more notice of them, except the crow. This bird cares for its young a long while, for as it flies past them it gives them food after they are able to fly. CHAPTER VII. 1. The cuckoo is said by some persons to be a changed hawk, because the hawk which it resembles disappears when the cuckoo comes, and indeed very few hawks of any sort can be seen during the period in which the cuckoo is singing except for a few days. The cuckoo is seen for a short time in the summer, and disappears in winter. But the hawk has crooked talons, which the cuckoo has not, nor does it resemble the hawk in the form of its head, but in both these respects is more like the pigeon than the hawk, which it resembles in nothing but its colour; the markings, however, upon the hawk are like lines, while the cuckoo is spotted. 2. Its size and manner of flight is like that of the smallest kind of hawk, which generally disappears during the season in which the cuckoo is seen. But they have both been seen at the same time, and the cuckoo was being devoured by the hawk, though this is never done by birds of the same kind. They say that no one has ever seen the young of the cuckoo. It does, however, lay eggs, but it makes no nest; but sometimes it lays its eggs in the nests of small birds, and devours their eggs, especially in the nests of the pigeon, when it has eaten their eggs. Sometimes it lays two, but usually only one egg; it lays also in the nest of the hypolais,[201] which hatches and brings it up. At this season it is particularly fat and sweet-fleshed; the flesh also of young hawks is very sweet and fat. There is also a kind of them which builds a nest in precipitous cliffs. [201] Sylvia curucca, hedge sparrow. CHAPTER VIII.