These birds lead a semi-nocturnal life, and frequent the margins of lakes, marshes, and rivers, where they feed on reptiles, frogs, and fish. They are generally of a shy nature, and live in solitude in the most unfrequented portions of extensive woodlands. When they want to seek their prey, they go into the water until it reaches half-way up their legs, and with the neck doubled down over the breast, and the head buried between the shoulders, they sometimes remain for hours together immovable as statues. If any fish glides along within reach of them, they suddenly stretch out their necks, as if impelled by a spring, and, with a sharp movement of the bill, impale the unfortunate victim. When their fishing is not very productive they dig into the mud with their feet, to turn out the frogs and other reptiles that are concealed in it. If compelled by hunger, they will attack rats, wood and field mice, and if further pressed they show no repugnance to carrion. They can, however, endure abstinence for a considerable time. Most of the Herons are endowed with great powers of flight. When compelled by unusually severe weather, they occasionally migrate, the young and the old travelling separately. Nevertheless, as they can accommodate themselves to almost any temperature, some species are stationary, and they are to be met with all the year round in countries the most dissimilar. The principal species of Herons are the Ash-coloured or Common Heron (Fig. 141), the Purple Heron, the White Heron, the Bittern, the Night Heron, and the Crab-eater. Every one knows the Grey Heron (_Ardea cinerea_), at least by reputation, if only from La Fontaine's verse:-- "Heron with the long bill, fit handle of a longer neck."