70 BIRDS' NESTS 



nest is made by the various species that breed in 

 holes or upon the ground; in fact, we may regard 

 some of these latter species as nestless, as, for 

 instance, the Ground Pigeons (Geophaps) of Australia, 

 which lay and incubate their two bufflsh-white eggs 

 upon the bare earth. With this exception the nests 

 of the Pigeons (a group of birds numbering nearly five 

 hundred species) are singularly uniform in type, a 

 fact which indicates an exceptional sameness in the 

 conditions of life of these birds. When placed in 

 trees or amongst vegetation of some kind the typical 

 Pigeon nest is merely a crude platform or flat mat 

 of sticks and twigs carelessly interwoven, and less 

 frequently intermixed with stalks and grasses, and 

 often so slightly made that the two white eggs can 

 be seen through the basket-like structure from below. 

 Unquestionably the nests of the Pigeons are by far 

 the crudest form of avine architecture attempted in 

 the branches ; yet we must take into consideration 

 the fact that the droppings of the old and young 

 birds accumulate and harden, and thus materially 

 strengthen the whole structure, as the time arrives 

 when it is required to support its maximum of weight. 

 Probably to this fact is due the prevailing low type of 

 architecture in this order of birds. That the crude 

 nest is amply sufficient for the needs of these birds 

 is proved by the fact that Pigeons are not only 

 exceptionally abundant as a group, but very widely 

 dispersed. The very crudeness of the nest renders 



