88 CICONIIFORMES 



CHAP. 



may often be seen standing ankle-deep in the water, and watch- 

 ing with untiring patience for the prey which never seems to 

 satisfy their appetite. They rarely swim and walk but little. 

 The majority breed in large colonies ; but Bitterns (Botaurus), 

 Little Bitterns {Ardetta), and Green Herons {Butorides) are 

 notable exceptions, being, moreover, skulking and nocturnal in 

 habit, and agreeing in the latter respect with Night -Herons 

 {Nycticorcix). The mud-flats commonly found on sandy shores 

 provide excellent feeding ground, and thence old and young may 

 be seen winging their way at considerable altitudes with leisurely 

 flapping flight rarely accelerated to roost at night on the 

 customary trees or rocks. Bitterns and their nearest allies are 

 seldom seen far from marshes, flying noiselessly with laboured 

 action and at a comparatively slow pace ; they are, however, 

 adepts at running or climbing among the water-plants, and 

 perch with ease ; while they often assume an upright position with 

 the bill vertical, and thereby closely resemble the surrounding 

 reeds, the deception being occasionally enhanced by the bird 

 turning as if on a pivot and facing the spectator constantly.-^ 

 Herons fly with the head drawn back, therein differing from the 

 rest of the Order, and in some cases roost or bask in the sun on 

 one leg ; they are usually graceful and stately, the beautiful 

 Egrets moving more easily on land than their kindred, and being 

 somewhat less wary. The voice is a harsh croak or guttural 

 sound, that of the Night-Heron verging upon a quack ; while the 

 Bitterns, besides the common cry, utter a booming or bellowing 

 note in the breeding season, generally heard at night or early in 

 the morning, the method of production of which is not at present 

 quite clear. Ardetta gives vent to a somewhat similar but 

 weaker boom or grunt, and most species are noisy at the nest, 

 hissing or screaming sharply. The diet consists largely of fish, 

 but is varied by small mammals, birds, reptiles, amphibians, 

 grasshoppers and other insects, molluscs, crustaceans, and worms, 

 the digestion being very rapid and the birds seldom gorged. In 

 the shallows the majority of the family stand motionless, and 

 spear their prey with the beak as it passes, occasionally mauling 

 it before swallowing ; but some move from place to place, while 

 the Buff-backed Heron (Ardea hubulcus) habitually picks insects 

 from the backs or sides of the cattle. The nest, commonly situ- 



Sclater and Hudson, Argentine Ornithology, ii. 1889, pj). 103, 104. 



