98 Wild Birds and their Haunts 



PECULIARITY OF BIRD VISION. 



It has been slowly brought to our understanding that 

 the world is not the same to all creatures, and probably, 

 says Science Siftings, no experiments have tended more to 

 make this clear than those by Professor Karl Hesz, of 

 Wuerzburg, on the colour-sense of chickens, pigeons, owls, 

 and kestrels. Men with hungry chickens and pigeons 

 were first kept an hour in a bright room to become 

 accustomed to the light. The floor was then spread 

 with a smooth black cloth, evenly covered with grains of 

 wheat, a strong spectrum was thrown on it from the 

 ceiling, and the hungry animals were turned loose. They 

 picked the wheat first from the bright red, then the 

 ultra-red, next the yellow, and finally the green. They 

 touched nothing in the blue and violet, because they 

 saw nothing ; but, on the other hand, they saw the grains 

 in the ultra-red that were invisible to the men. This 

 proved that for chickens and pigeons the spectrum 

 is shortened at the violet end of short-wave length and 

 extended at the red end of long-wave length. This is 

 the effect one might expect from wearing orange-coloured 

 glasses, and Hesz demonstrated that fowls see through 

 such spectacles in the form of yellow and orange oil- 

 globules embedded in the light-sensitive layer. To 

 kestrels and bussards the brightest zone was the green 

 instead of the red, the blue being visible. To owls the 

 colours were as men see them. 



