440 The Bird 



large complement of eggs (eight to twenty) in order to 

 bring to maturity enough young to replace the yearly 

 mortality, for the ground-built homes and huddling chicks 

 encounter a multitude of dangers to which birds in trees, or 

 even the small-sized ground-nesters, are not exposed. One 

 exception here singularly favours the rule. The Thibetan 

 Peacock Pheasant inhabits the heights of the Himalayas, 

 where it has to contend with only three or four nest- 

 robbers, instead of the countless foes that infest the lower 

 jungles; hence its ample breast warms but two eggs. 



'' The doves and pigeons lay only two eggs, and a few 

 lay but one; but this seems to be due to the fact that 

 their extraordinary powers of flight render them, as adults, 

 unusual immunity from capture and famine, rather than 

 to am^ special safety pertaining to their m.ethod of nidifi- 

 cation. 



" Hawks and owls in general have four or five eggs, 

 and as this is about the average number of the small 

 birds on which they largely prey, it seems evident that 

 their chances of life and the difficulty of sustaining it 

 are, on the whole, no less than are met with by their 

 victims. The owls, however, vary much among them- 

 selves in this respect; the Snowy Owls, whose home is in 

 the snowy north, where a nest in the tundra moss is acces- 

 sible to every marauder, and the Burrowing Owls, whose 

 underground homes are constantly robbed, being obliged 

 to lay twice as many eggs as the remainder of the family 

 in order to overcome the high percentage of casualties 

 due to these unfortunate situations. 



" An odd feature in the nidification of some of the 



