THE FERN-OWL. 
261 
With all these united powers, swift and silent too in flight 
as it is, no wonder that this bird makes such havoc amongst 
the, to us nearly invisible, multitudes that people the silent 
air on a summer’s night. At twilight, it may sometimes he 
seen at work, flitting about, hovering now over one spot, 
then over another, occasionally dropping or tumbling over, 
as if shot ; this is the moment, when having seized a moth, 
the bird reaches it to its mouth, and loses its balance, when 
again rising, it glides away like a ghost, till lost in shade. 
We have but one species visiting England, hut in foreign 
countries there are many. In South America, particularly, 
they abound: the curious retreats of one species of these 
birds are thus described by the celebrated traveller, M. de 
Humboldt, who visited a dark chasm in the rocks called the 
cavern of Guacharo, frequented by a species ( Ccvprimulgus 
j steatornis ) whose young were caught to furnish oil : — * 
“ A frightful noise, made by these birds, issued from the dark 
recesses of the cavern ; their shrill and piercing tones rever- 
berated from the arched roofs, and re-echoed from the depths of 
the cave. The Indians, by fixing torches to the end of a long 
pole, pointed out their nests, arranged in funnel-shaped holes, 
with which the whole roof of the grotto was riddled. As the 
travellers advanced, the noise increased, the flare of the torches 
alarming the birds still more. When it ceased for a few minutes, 
distinct moans were heard from other remote branches of the 
cavern, the alternate responses of other flocks of these birds. The 
Indians, every year about Midsummer, descend into the cave, 
furnished with poles, for the purpose of destroying the nests. 
At this time many thousands of birds are killed, and the old 
ones, as if to protect their broods, hover over the heads of the 
Indians, uttering the most dreadful shrieks. The young that 
fall to the ground are immediately ripped open, to procure a 
sort of unctuous or fatty substance with which they are then 
loaded. At this period, which is commonly termed the oil- 
harvest, the Indians construct little habitations of palm- 
leaves, close to the opening, and even in the mouth of the 
cavern. Here the grease of the young birds just killed 
is melted over a fire of dry sticks, and run into pots of white 
clay. This grease, known by the name of Guacharo butter 
