THEIR REPRODUCTION (NESTS) 247 



gradually accumulated (the birds frequenting the 

 spot all the year round), the indigestible parts 

 of the food that are cast, and upon this bed 

 the eggs are deposited. The Hornbills are also 

 remarkable for their very singular methods of 

 nidification. They breed in holes in trees, a 

 circumstance about which there is nothing very 

 remarkable in the present order ; but as soon 

 as the eggs are laid, the female either builds 

 herself in the hole, or the male does so for her, 

 plastering up the entrance until but sufficient 

 space is left for the cock bird to pass food to 

 her. Here a voluntary prisoner she remains 

 until her task is done, emerging emaciated and 

 with worn and draggled plumage when the eggs 

 are hatched. It is worthy of remark that in 

 the Hoopoes the females evince a similar dis- 

 inclination to leave the nest hole, the males 

 feeding them during the whole period of incuba- 

 tion. Then in the nidification of the Swifts there 

 is much of exceptional interest, for to this family 

 belong the species which make the famous edible 

 nests, so highly prized in the Far East as articles 

 of food. These birds, belonging to the genus 

 Collocalia, breed in caves. The best quality of 

 these nests resembling isinglass, and formed from 

 a gelatinous secretion from the salivary glands, 



