3. These birds make their nests in a place sheltered from the wind. That which the Beotians call ærops[191] is the only bird that makes its nests in caverns in the earth. The cichlæ[192] make nests of mud like swallows in the tops of trees; but they place them in order close to each other, so that from their proximity they look like a chain of nests. Among the birds which make solitary nests, the hoopoe makes no real nest, but lays its eggs in the stumps of hollow trees, without building at all. The coccyx[193] lays its eggs in houses and holes in rocks. The tetrix, which the Athenians call "urax," makes no nest on the ground or in trees, but in herbaceous plants. [191] Merops apiaster. [192] Turdus, thrush. [193] Cuculus canorus. CHAPTER II. 1. The eggs of all birds are alike and have a hard shell, if they are produced by sexual intercourse and are not decayed, for domestic fowls sometimes lay soft eggs. Birds' eggs are two-coloured, externally white, internally yellow. The eggs of birds inhabiting the sides of streams and lakes differ from those living on dry land, for in the eggs of aquatic birds the yolk bears a much larger proportion to the white. 2. The colours of eggs vary in different kinds of birds. Some have white eggs, as pigeons, partridges; some yellow, as those inhabiting streams; others are spotted, as those of the meleagris[194] and phasianus;[195] the eggs of the cenchris are red like vermilion. In the egg itself there is a difference; for one end is pointed, the other round. The round end is produced first. The large, sharp eggs are males; those which are round and circular at the sharp end are females. [194] Numida Meleagris. [195] Phasianus colchicus. 3. They are matured by incubation. Some are hatched spontaneously in the earth, as in Egypt, being buried in dung; and they say that in Syracuse a drunkard placed eggs beneath his mat, and drank without ceasing until the eggs were hatched; and eggs placed in warm vessels have been matured and hatched spontaneously.