62 
SEXUAL SELECTION : BIRDS. 
Part II. 
fallen tree/’ or, according to Audubon, against liis own 
body ; the sound thus produced is compared by some to 
distant thunder, and by others to the quick roll of a 
drum. The female never drums, ^^but flies directly to 
the place where the male is thus engaged.” In the 
Himalayas the male of the Kalij -pheasant often makes 
a singular drumming noise with his wings, not unlike 
the sound produced by shaking a stiff piece of cloth.” 
On the west coast of Africa the little black-weavers 
(Ploceus ?) congregate in a small party on the bushes 
round a small open space, and sing and glide through 
the air with quivering wings, which make a rapid 
whirring sound like a child’s rattle.” One bird after 
another thus performs for hours together, but only during 
the courting-season. At this same season the males of 
certain night-jars (Caprimulgus) make a most strange 
noise with their wings. The various species of wood- 
peckers strike a sonorous branch with their beaks, with 
so rapid a vibratory movement that the head appears 
to be in two places at once.” The sound thus pro- 
duced is audible at a considerable distance, but can- 
not be described ; and I feel sure that its cause would 
never be conjectured by any one who heard it for the 
first time. As this jarring sound is made chiefly during 
the breeding-season, it has been considered as a love- 
song ; but it is perhaps more strictly a love-call. The 
female, when driven from her nest, has been observed 
thus to call her mate, who answered in the same 
manner and soon appeared. Lastly the male Hoopoe 
{Upupa epops) combines vocal and instrumental music ; 
for during the breeding-season this bird, as Mr. Swinhoe 
saw, first drawls in air and then taps the end of its 
beak perpendicularly down against a stone or the trunk 
of a tree, when the breath being forced down the 
tubular bill produces the correct sound.” When the 
