THE PERCEPTION OF SPACE 



685 



WTiile these constitute the main types of field in Birds, it is to be expected 

 that in a class so diversified exceptions exist. Some pengviins {Spheniscus) have 

 no binocular field. The snipe has eyes set far back in its head giving a consider- 

 able jDOsterior binocular field so that it can see a potential enemy behind and 



Fig. 829. — The Bittern, Botavrus stellaris. 

 A delightful photograph showing how adept the bittern is at concealment. 

 When disturbed among the reeds it stretches its neck with the beak pointing 

 upwards and stands motionless so that the dark stripes running down the 

 neck and breast feathers blend with the reeds among which it hides. In the 

 meantime, the downwardly directed ej'es get an tmimpeded view and the bird is 

 enabled at the same time to watch its larood at its feet (Burton's iStor^ of Animal 

 Life, Elsevier Pub. Co.). 



above when feeding, while the bittern with its downward-pointing eyes has a 

 ventral binocular field so that it can still see dowTiwards with both eyes when 

 standmg camouflaged among the reeds with its beak pointed upwards towards 

 the sky to simulate another reed (Fig. 829). Occasionally a single tj^De may 

 differ widely from the characteristics of the family ; thus alone among parrots 

 the kakapo of New Zealand {Stringops labroptilus) and alone among ducks the 



Stringops 



