Locomotion in Young Birds. 69 



several birds of this species," he adds, " all of which dived 

 with the young under their wings. The young were placed 

 with their heads towards the tail, and their bills resting 

 upon the back of the parent bird." It must be remem- 

 bered that the grebes and divers do not use the wings for 

 progression under water. 



Before leaving the activities connected with swimming, 

 attention may be drawn to the curious habit observed by 

 Mr. Thomson, head keeper at the Zoological Gardens. 

 " Birds which sleep floating upon ponds or tarns," says 

 Mr. Headley,* commenting on this habit, " are in danger 

 of drifting to the bank and falling victims to any beast 

 of prey. To prevent this the ducks and others have the 

 habit of sleeping with one leg tucked under the wing, while 

 with the other they keep gently paddling so that they 

 revolve in a circle. In summer-time, when they have had 

 a long day, they will begin this early, when there is still 

 some light, and then is the time to watch them. This 

 remarkable habit is a kind of sleep-walking turned to good 

 account, and is, no doubt, perfectly compatible with com- 

 plete unconsciousness." It would be interesting to ascer- 

 tain if this habit be truly instinctive, and how the paddling 

 in a circle would prevent their drifting ashore. That the 

 locomotor activities concerned in swimming and diving are 

 congenital, though no doubt subject to improvement and 

 modification by practice and individual acquisition, admits, 

 I think, of no question. 



Passing to the powers of flight possessed by birds, it is 

 clear that, if a truly instinctive activity, it is, in the great 

 majority of birds, of the deferred type. Spalding kept 

 young swallows caged until they were fully fledged, and 

 then allowed them to escape. " One, on being set free, 

 flew a yard or two close to the ground, and then rose in 



* " The Structure and Life of Birds," pp. 171, 172. 



