BLUE NILE AND DINDER RIVER 
313 
As each evening- deepened towards dusk, there appeared 
from off the ocean-like expanse of stubble upon our right 
—that is, west—what resembled dusky clouds, composed 
of millions of wheeling, revolving, palpitating atoms, now 
rising in air, anon shooting down earthwards as by a single 
simultaneous volition. These were weaver-finches ( Quelea 
ezthiopica , with bishop-finches, Pyromelana franciscana , 
Hyphantornis galbula , and possibly other species) bound 
for their roosts in the forests beyond the river. Each 
separate cloud might occupy half a mile of space, followed 
in unbroken succession by others no less extensive. One 
evening I minuted the procession—-there were armies 
passing in front, others overhead, equal numbers behind, 
as far as eye could reach in either direction. It lasted 
fifty-five minutes! As these hosts crossed the river 
some dipped to its surface—presumably for an evening 
drink upon the wing. Now birds of prey, as a rule, shun 
contact with such massed formations ; but here predatory 
instinct had divined a method of exploiting the opportunity. 
Grey goshawks ( Melierax) and falcons hovered attend¬ 
ance on the wealth of flying food. By a “demonstration 
in force ” from above, alarm was spread through the ranks. 
The whole flight dipped and the lower strata were thus 
forced by hundreds into the water beneath. Then the 
strategists coolly helped themselves—each to a double 
prize, right and left! Whole battalions, it might appear, 
perished aimlessly; since Nature never recks of the 
individual life. Yet nothing, in fact, was wasted. The 
crocodiles, with hordes of predatory fish and other sub- 
aquatic carnivores, saw to that. 
Riding onwards in glowing twilight, the thought 
occurred that when Lord Kitchener’s barrage has 
materialised and this whole region has been reduced to ‘ 
a granary, auxiliaries more potent than goshawk or 
falcon will be required to hold in check these myriad 
armies of grain-eating finches? 
In the second instance, other birds, while guiltless of 
