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 (Lotaurus), 
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 
(Wycticoraz). 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 bubulcus) habitually picks insects 
from the backs or sides of the cattle. The nest, commonly situ- 
1 Sclater and Hudson, Argentine Ornithology, ii. 1889, pp. 103, 104. 
