THE LIVING BIRD 23 



had not even been laid as an egg when the nest in 

 which it was reared was under construction nor did 

 it stop to study its architecture before struggling out 

 of it. Yet a year later, on its own initiative it pro- 

 duces a wonderful fascimile, correct to the minutest 

 detail. A canary reared in a machine-made nest of 

 felt will unhesitatingly construct its own from grass 

 and moss the year following if forced to do so. It 

 will even built it in a bush like a wild bird if no 

 frame is provided. This is instinctive behavior in 

 its most highly developed form. But even in- 

 stinctive behavior is subject to modification under 

 the guidance of experience and it is usual to find 

 old birds much more deft and individualistic in 

 nest building than the immature. Practice un- 

 doubtedly makes perfect even among birds. Yet 

 when real intelligence is called for, birds fail. Thus 

 the European jackdaw (Coloeus monedula), which 

 often builds in hollow trees, will occasionally find 

 a hole without a bottom. Instead of spending the 

 usual few hours dropping in sticks for the base of 

 the nest, jackdaws may persist for days without 

 discovering that they are attempting the impossible. 

 Dippers {Cinclus cinclus) occasionally select the 

 girders of small bridges in Yorkshire for their nests. 

 The repetition of convenient spaces side by side, is 

 generally more than they can comprehend and it is 



