56 J. C. Douglas — On the Perching of Birds. [March, 



be moved, slipping is still further guarded against, by turning in the nails 

 so that their points touch the perch. If the perch be violently swung, the 

 bird bends his legs, and rests with his breast on the perch, thereby lowering 

 his centre of gravity. If a live bird be perched on the finger, it will be felt 

 that it balances itself and does not grip, but it frequently uses the points 

 of its claws, particularly of the hind ones. It the hand be moved forwards, 

 the bird having a tendency to fall backward, it will be found to actually 

 raise its front toes, and stick in the points of the hind claws ; far from 

 gripping tighter, it actually grips less tightly. If a sleeping bird be shaken, 

 it awakes and puts down its second foot. If the perch be swung while the 

 bird is asleep, the bird will be observed to move its body in advance of the 

 movements of the perch. Although the sleeping bird usually uses the 

 point of his hind nail, he does not always do so, and sometimes sleeps, 

 obviously not holding the perch, but evidently balancing, the perch being 

 stationary, but if the perch be moved slightly, the hind nail is used 

 immediately. I cannot detect any bending of the leg, when the bird goes 

 to sleep, beyond that which exists when it is awake, nor is the flexure of the 

 last joint of the toes accompanied by a bending of the leg under ordinary 

 circumstances. On the other hand there can be no doubt, that, in the live 

 bird, flexure of the toes is independent of bending of the leg ; a live bird 

 can open or close its claws, with the leg straightened, or bent close to the 

 body, and if a bird be under the influence of either, the flexure of leg and 

 foot, simultaneously observed in the dead bird, is not observed. Birds com- 

 monly rest with the .breast on the perch, in these cases, the claws will be 

 found quite open ; it is obvious in this case, that flexure of knee and heel does 

 not cause flexure of the toes. 



If bending of the leg necessarily caused flexure of the toes, the bird 

 would in some cases evidently be inconvenienced, during incubation for 

 instance. The idea, that the weight of the body tending to bend the leg 

 might so flex the toes as to diminish the fatigue of perching, is obviously 

 erroneous mechanically ; for, if the grip of the perch were produced by the 

 contraction of particular muscles, and if the same muscles were employed 

 on the additional labour of preventing flexure of the leg, the two duties 

 would not be so opposed as to make the strain on the muscles less than it 

 would be if they performed but one duty, and the additional duty would in- 

 crease the load not decrease it. It appears to me, that perching birds really 

 balance themselves, just as mammals and birds on plane surfaces do ; that 

 they are enabled to do this just as man is, by means of opposing muscles ; 

 that flexure of leg and toes are independently under control of the bird's 

 will as in man ; and that the movements found dependent on each other in 

 the dead bird after alteration of the muscles, are independent in the live 

 bird ; and that the large surface covered by the toes, the relative lightness 



