INTRODUCTORY 27 



also do certain Raptores, Herons, Coots, Moor-hens, 

 Grebes, Ducks and Swans — nests that exhibit the same 

 principles as those of the smaller birds, but, of course, 

 carried out on a much larger scale. Again, what 

 difference is there between the nest-building tools 

 of the Kestrel and the Sparrow- Hawk ? Yet the latter 

 builds a fairly made nest, and the other never makes 

 a nest at all and rears its young in the deserted nests 

 of other birds, or on the ledges of cliffs, on no other 

 resting-place than the bare rocks or the refuse of its 

 food. In fact, in no other group of birds are the tools 

 of more equal merit and the architectural results so 

 various, for we have species most elaborate and clever 

 nest-builders, species that make nests on the trees and 

 the cliffs and on the bare ground, whilst the nests of 

 others are slight, often crudely made, and in not a few 

 cases are dispensed with altogether (as in many of the 

 Falcons), or some deserted home of another and very 

 different species is annexed for the purpose. The 

 Woodpeckers, the Kingfisher, the Starling, and some- 

 times the Jackdaw, well provided with the requisite 

 appliances for building an elaborate nest, rear their 

 young in structures poorly fabricated in the holes of 

 trees, rocks, banks, or buildings, or do not make a 

 nest at all. In some entire groups (as in the Parrots 

 and certain Picarian species) we find an utter absence 

 of architecture, notwithstanding the fact that the 

 birds seem in every way adapted for making elaborate 

 nests. From all these interesting facts I think that 



