They had been much interested in watching the huge flocks of small birds of the linnet kind which assembled half an hour before sunset and went to drink together in the pools of the Atbara. They come with an undulating flight, and, small as they are, the rushing of the wind as they beat the air makes a noise like thunder, and their numbers darken the sky. The weight of the throngs of them which alight at a time bends down the ends of the overhanging branches and twigs to the level of the water. I had seen these flocks many times, and the cunning trick which the crocodile uses in preying upon them. This was a point of Soudanese natural history which did not escape the observation of Sir Samuel Baker. “Few creatures are so sly and wary as the crocodile. I watch them continually as they attack the dense flocks of small birds that throng the bushes at the water’s edge. These birds are perfectly aware of the danger, and they fly from the attack if possible. The crocodile then quietly and innocently lies upon the surface, as though it had appeared quite by an accident; it thus attracts the attention of the birds, and it slowly sails away to a considerable distance, exposed to their view. The birds, thus beguiled by the deceiver, believe that the danger is removed, and they again flock to the bush, and once more dip their thirsty beaks into the stream. Thus absorbed in slaking their thirst, they do not observe that their enemy is no longer on the surface. A sudden splash, followed by a huge pair of jaws beneath the bush that engulfs some dozens of victims, is the signal unexpectedly given of the crocodile’s return, who has thus slily dived, and hastened under cover of water to his victims. I have seen the crocodiles repeat this manœuvre constantly, they deceive by a feigned retreat, and then attack from below.”[113] These birds fall a prey not only to crocodiles but to large fish—of what species I am not sure—which rise at them as other kinds rise at flies and snap them off the twigs. Besides, kites scout about the outskirts of the flocks as they fly and pick up the stragglers. In this part of the country we saw baobab trees only on the banks of the river. Elsewhere, the trees are all mimosas and the undergrowth of the same order.