148 CHILDHOOD OF ANIMALS 



cannot refrain from eggs, and the fierce and bloodthirsty stoats; 

 weasels and their allies are relentless persecutors of birds. Monkeys, 

 and man himself, are still more crafty and diligent in seeking out nests. 

 I do not know any monkey that will refuse an egg, and even the 

 great apes, which are amongst the most vegetarian of the Primates, 

 greedily devour eggs in all stages of incubation, as well as nestlings 

 and young birds. The civilised boy, birds '-nesting in the hedge- 

 rows, or scaling tall trees to add to his collection, is pursuing one of 

 the oldest habits of his ancestors. 



It is almost a wonder that any eggs hatch into nestlings, any 

 nestlings survive to be fledged, or fledglings reach the relative safety 

 of adult life. And yet the eggs are so cunningly placed, and the 

 young so zealously guarded, that the limitation of the family has 

 reached much further than in the lower groups. The ostrich, it is 

 true, lays about thirty eggs, but this is an extreme instance. Birds 

 such as pheasants, partridges and other ground birds, which fly 

 badly and are specially exposed to the dangers affecting the young 

 of all birds, may lay as many as twenty eggs. Most of the smaller 

 arboreal birds lay not more than four or five eggs. Pigeons, 

 birds-of-prey and humming-birds usually lay two, and many sea- 

 birds such as petrels, divers and guillemots lay only one. So also 

 most birds breed only once a year, but, if the first brood be destroyed, 

 they may lay a second time. 



Brood-care begins with the selection of a suitable place for the 

 deposition of the eggs. Occasionally degraded individuals, if we 

 take the ethical point of view, or unusually intelligent individuals, 

 if we take a view more consonant with human individualism, will 

 make use of the abandoned nest of other birds, or will turn out the 

 occupants of an inhabited nest, and use it for their own purposes, 

 and in some species this has become a habit. The cow-birds 

 or American starlings (Molobrus) are on the way to lose the nest- 

 building instinct which they once possessed. The Argentine 

 cow-bird has been seen by Mr. W. H. Hudson trying to build, but 

 failing in the effort. The females hang about the nests of other 

 birds, particularly the mud houses of oven-birds, and if they find 

 one that has been broken into, they lay their eggs in it. When 

 nesting-boxes were placed in trees, the cow-birds were the first 

 to visit them, inspecting them with mingled fear and curiosity, 

 but finally using them. Other cow-birds lay their eggs in the 

 occupied nests of other birds, and as their eggs develop very quickly, 

 the young hatch out before the legitimate occupants and rob them 



