156 BRITISH SEA BIRDS. 



winter visitor. At that season, however, it may 

 be met with pretty frequently off the British coasts, 

 the young birds especially venturing into our bays 

 and creeks and estuaries, older individuals, as a 

 rule, keeping further out to sea. Adult birds are, 

 however, often observed near the coasts of South 

 Devonshire and Cornwall. I have known them 

 linger in the waters near here until the summer has 

 been well advanced. Young birds of this species, 

 in the brown and white dress characteristic of im- 

 maturity, may often be seen quietly fishing under 

 the cliffs, notably in Tor Bay. One very remark- 

 able thing about this Diver is its singular habit 

 of immersing the body to such a depth that the 

 back is quite under water. It often so sinks itself 

 when menaced by danger, and then, almost out 

 of sight, swims away with great speed. If pursuit 

 is still continued all but the neck is sunk below the 

 surface, and finally, if hotly pressed, the bird will 

 disappear entirely, and swim along under water 

 at a speed absolutely astonishing, Gatke records 

 that this Diver, when chased by a boat under these 

 circumstances, will dive and allow the boat to pass 

 over it, rising again in the rear of it, a habit which 

 my own observations of the bird completely 

 confirm. How this act of immersion, without 

 apparent effort, is accomplished remains a mystery, 

 and offers a problem in animal mechanics by no 

 means easy of solution. 



The Great Northern Diver is rarely seen on 



