THE LOVE DISPLAYS OF BIRDS 227 



peculiar to the adult males ; and in one species 

 at least (Selasphorus) we know that the flight 

 during the mating season is accompanied by 

 a shrill screeching noise said to resemble the 

 sound made by a wood splinter touching a cir- 

 cular saw in rapid motion ; the bird rising to 

 some height and then descending like a flash, 

 making the singular sound which does duty for 

 a love note or song. This attenuated first pri- 

 mary is found in various birds very remotely 

 related. It occurs in the American Woodcock, 

 in the South American Guans, the Indian Lesser 

 Florican, and Pallas's Sand-Grouse. The male 

 of one species of Guan (Penelope nigra) is 

 known to make a crashing noise like that of 

 a falling tree, as he flies downwards : the Flori- 

 can produces a deep-toned humming sound. 

 The various modifications of the secondary 

 quills are no less remarkable. Perhaps the most 

 curious instances are furnished by the Manakins. 

 Many of these species have the shafts of the 

 secondaries abnormally thickened and the webs 

 of various shapes. Even the bones of the wing 

 are exceptionally strong and thick. These mo- 

 difications are also dimorphic, confined to the 

 male, the corresponding feathers in the wing of 

 the female being of the normal shape. Most 



