240 BIRD BEHAVIOUR 



species where they meet in their breeding-range 

 outside Britain, as in Central Siberia. Here also 

 our Goldfinch breeds and interbreeds with the 

 Grey-headed Goldfinch of the Himalayas (Carduelis 

 caniceps), a bird provided with excellent recognition 

 marks. Actual specimens illustrating these points 

 can be seen in the Entrance Hall at the South 

 Kensington Museum. 



American naturalists will recall the case of the 

 Red-shafted and Yellow-shafted Flickers (Colaptes 

 cafer and C. auratus), two inter-breeding Wood- 

 peckers also well distinguished by hues and patterns, 

 and Anglo-Indians that of the Indian and Burmese 

 Rollers or " Blue- jays " (Coracias indica and C. 

 affinis), the latter much darker than the former, and 

 devoid of its conspicuous terminal tail-bar, yet 

 producing numerous intergrades, while the pure 

 forms, as in the case of the Crows, have actually 

 been seen paired up together. 



Many similar cases might be cited ; in fact, just 

 where " recognition-marks" might be expected to be 

 of service, there they uniformly prove inoperative 

 to segregate species as might indeed have been 

 expected when we see our variable domestic birds 

 infallibly recognize their own species in spite of 

 abnormalities in colour. 



Neither does the study of the courtship of birds 

 exhibiting colour-variations encourage the idea of 

 preference for a particular type of colour. Sir 

 Ralph Heron recorded, nearly a century ago, how 

 all his Peahens fell in love with a pied Peacock, and 



