BLUE NILE AND BINDER 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 

 czthiopica, 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 



