406 



The Bird 



One interesting analogy to the fin of a fish is found 

 in the tail of the Blue Duck of New Zealand. This bird 

 lives in swift mountain streams and when swimming carries 

 its long tail entirely submerged. By vigorous sidewise 

 flicks of these tail-feathers it can turn around, as if on a 

 pivot, without being carried down-stream, even when 

 in the centre of a rapid, swirling current. 



PIG. 322. Murre showing tail. (Compare with Fig. 246.) 



It is interesting to compare this use of the tail-feathers 

 with the function of the tail in the flightless penguins. 

 In the Black-footed species, at least, the tail-feathers are 

 stiff and short, but the bones of the tail are unusually 

 elongated and the flesh which covers them is flattened 

 into a kind of vertical rudder. Strong muscles control 



