DR. EMIL HOLUB. 197 



to rest, and soon they are asleep. But do not think, dear 

 reader, that with the retirement of the Swallows every sign 

 of life has ceased in the dark marsh for the night. Though 

 the night has set in, we soon hear peculiar low tones coming 

 from the thicket of reeds. We hear the melancholy song 

 of the Sylvias, the voices of the Night Herons and of the 

 Bitterns, and from time to time the gurgling cry of the 

 sentinel among the gray Cranes mingles with them, generally 

 followed up by the cries of the whole troop of Cranes. 

 Another Crane takes the watch until his cry again puts these 

 large birds on the alert against the sly attacks of hyenas and 

 jackals. 



The day is dawning. The song of the gray Sylvias and 

 the Bittern's loud boom are soon drowned in the noise of the 

 hundreds of thousands of Swallows which have just awak- 

 ened, and in the loud cries of the large birds, which try at 

 first a walk on the moist bank of the swamp, before they 

 leave for the plains. Our friends, the Swallows, rise after a 

 good deal of squabbling about the dreams of the night past ; 

 they leave in small swarms — as I think, those coming from 

 certain European districts keeping together for the whole 

 time of their African sojourn — and make at once for the 

 different portions of that endless plain, on which they are 

 accustomed to hunt day after day. But they do not rise high 

 up in the air to fly in any particular direction ; taking the 

 proper course at first, they commence at once to search for 

 food, reaching their proper hunting-field — may it be near or 

 very far off — by thus flying low along the high grass, and 

 taking with their breakfast the glittering drops of the morn- 

 ing dew to quench their thirst. 



Who could count the millions of insects the swarms of 

 Swallows which rest at this one marsh destroy in a single 

 day on that South African plain } Count now all the sleep- 

 ing-places ; count now all the swarms of this most useful 

 bird ; consider also the number of days of our winter, dur- 

 ing vjhich the Sv^^allows remain in the far south ; and if 



