60 
SAVAGE SUDAN 
appearances of each are roughly shown in various diagrams 
passim . Then take the fish-catching birds. Both darter 
and cormorant capture their prey by fair chase under 
water ; yet while one needs a strongly hooked beak, the 
other dispenses with a hook but substitutes, in lieu thereof, 
serrated mandibles. The herons are no less adepts but 
need neither hook nor serration, though the rim is 
slightly roughened. The question, however, is too big 
to discuss here—mergansers, grebes, gannets would all 
have to be called as witnesses. All are built for a similar 
object; yet, while all differ in 
armament and equipment, 
all equally succeed. It may 
be held there are causes 
assignable to every effect, a 
reason for each fact; if so, 
in these cases the predispos¬ 
ing factors lie far beyond the 
range of our finite vision. 
Of the egrets I write in 
diary:—-“The great white 
egret of Nile is bigger than 
any seen in Spain. It is 
Herodias alba , and has a 
yellow beak and black legs. The middle-sized egret 
(H. brachyrhynchus) has black beak and yellow legs, 
while in the little egret (//. garzetta) both beak and 
legs are black. Why? Their style of fishing differs 
from that of the herons. The latter stand statuesque 
as though carved in granite, awaiting the approach of 
prey, and make but a single spear-thrust. Patience is 
their policy ; whereas the egrets are ever hunting actively 
about the shallows, and frequently put in a short run, 
followed by several consecutive strokes, quick as lightning. 
“A flight of weaver-finches sweep down to the river’s 
edge for a drink, alighting close by a big white egret. 
Him the thirsty crowd suspect not. Suddenly, with three 
Glossy Ibis. 
