132 OUR SUMMER MIGRANTS. 



been thus stated : " They consist, so far as we 

 can ascertain, merely in the presence of a bright 

 buff or pale cinnamon tinge on the breast of the 

 male in A. rupestris, and perhaps in that form 

 being of a slighter build than A. obscurus. In 

 the female of the so-called A. rupestris the warm 

 colour is much more faintly indicated ; in some 

 specimens it is doubtful whether it exists at all. 

 The outer tail feathers, which in A. spinoletta 

 afford so sure a diagnosis, are in A. rupestris 

 just as dingy as in A. obscurus!' 



There can be no doubt that the chemical con- 

 stituents of colour in the plumage of birds are 

 always more or less affected by climatic agency; 

 and, this being so, one can hardly be justified 

 in founding a new species on mere variation of 

 colour, where there is at the same time no 

 modification of structure. There can be little 

 doubt that the Scandinavian Rock Pipit is iden- 

 tical with our own bird, the slight differences 

 observable being easily accounted for through 

 climate and the season of the year at which 

 specimens are obtained. 



