Figure 7. The Carrick blindfold. Made of 

 light, opaque paper. The size and shape 

 vary according to the species. 



ing steady posture. In short, the duck does not need to see its surroundings 

 in order to keep the balanced position of its head. 



Not only is the blindfolded bird able to balance its head when held in 

 the hand, but when it is cast into the air, body and head quickly assume the 

 posture of flight. Like a cat falling with its feet to the ground, the blind- 

 folded bird quickly adjusts to its belly-down flight attitude when cast aloft. 

 A blindfolded Blue-winged Teal, or any other duck, when thrown into the 

 air with tail or belly upward, twists in a flash to flight posture and flies away. 

 In experiments designed by William H. Carrick (1949) we flew 249 blind- 

 folded birds of eighteen species at Delta between 1946 and 1952 (Figure 

 7).° Regardless of how these blindfolded birds were cast into the air, suc- 

 cessful flight was the rule rather than the exception and only 5 per cent 

 refused to fly. 



The ability of birds to right themselves and fly when they cannot see 

 their surroundings or the sun depends heavily upon the balancing function 

 of the vestibule of the ear with its semicircular canals and otolith organs 

 (Lowenstein, 1950; Wendt, 1951). Wendt points out, however, that muscle 

 receptors also play an important role in establishing body posture and "it is 

 not always easy to separate vestibular effects from other factors." Paton 

 (1928), who studied the equilibrium of the domestic Mallard, concluded 

 that "some visceral change is produced as a result of the disturbance of 



• The species flown with blindfold were : Mallard, Pintail, Green-winged Teal, Blue- 

 winged Teal, Redhead, Marsh Hawk, Cooper's Hawk, Wilson's Snipe, Great Horned Owl, 

 Barn Swallow, Catbird, English Sparrow, Bronzed Grackle, Yellow-headed Blackbird, Red- 

 winged Blackbird, Cowbird, Song Sparrow, Crow. 



62 



