66 BIRDS OF LA PLATA 



in the old habit of building , exposed nests would 

 perish* Domed nests made by Dendrocolaptine birds 

 are very abundant even now, and it is probable that, 

 before the country became settled by Europeans, 

 they were very much more numerous* Darwin, 

 speaking of the Oven-bird's habit of always placing 

 its oven in the most conspicuous and (to man) access- 

 ible places, predicts, and truly I believe, that this 

 habit will eventually cause the extinction of the 

 species ; for when the country becomes more thickly 

 settled, the bird-nesting boys will destroy all the 

 ovens. Probably when the Oven-birds were more 

 abundant the Sparrows could always find vacant 

 ovens to breed in, until a habit of breeding almost 

 exclusively in these safe and convenient bird-built 

 houses was acquired ; and the present seemingly 

 stupid persistence of the birds in struggling to get 

 possession of those already occupied by stronger 

 species, only shows that the habit or instinct has not 

 been modified to suit a change in the conditions 

 i.e. t a diminishing number of ovens to breed in, 

 with perhaps the increase of other stronger species 

 possessing the same habit. But while the in- 

 stinct thus survives too strongly in the country 

 birds, many individuals have taken to a town life, 

 and acquired the new habit of breeding in holes 

 in brick walls* Probably this race of town birds 

 will eventually colonise the rural districts, and 

 usurp the place of the country birds, which will 

 then be placed at a disadvantage. 



