204 THE ZOOLOGIST. 



I have made a great number of careful observations, calcula- 

 tions, and experiments on various species of birds, but I hardly 

 think it necessary to take more than a single instance, and that 

 the Little Grebe. The Lathkill and several other of the neigh- 

 bouring Derbyshire streams provided admirable conditions for 

 making the necessary observations, and for checking the experi- 

 ences of other districts. When a family party dozing in the 

 middle of a pool was alarmed, they all disappeared below the sur- 

 face and remained submerged, with the exception of their heads 

 or bills. I was not able to be sure how they held themselves below 

 the water, but see no reason to doubt that use was being made 

 of the rank vegetation — probably by the inward pressure of the 

 flexed toes, as I have described. Yet this detail is not of great 

 importance. 



In time, if reassured by the stillness of the intruder, the 

 Grebes would appear again, but very gently and unobtrusively, 

 and in a while they would take up their positions at the surface, 

 perhaps in the centre of the pool, away from the vegetation. It 

 was easy to watch the slow transition from a state of total sub- 

 mergence—so far as the body was concerned — to one where 

 the birds floated, balls of feathers, high on the water. Those 

 familiar with Grebes (or almost any other species of water birds) 

 must have noticed this occasional habit of floating nearly as 

 lightly as a Gull. 



At each distant alarming sound the Little Grebes would drop 

 suddenly deeper in the water, the degree in the change of draught 

 varying with the source of the alarm ; and when danger seemed 

 imminent, and the birds dived, a preliminary drop in the water 

 indicated a sudden change in the specific gravity. The Moorhen 

 acts in the same way when alarmed, but this instinctive feather 

 adjustment, for another purpose, however, is seen most prettily 

 in its relative, the Water-Kail ; at each forward step, if only for 

 a couple of inches, the flank-feathers are automatically pressed 

 close to the sides, so that a cross section of the body would 

 give not a circle but a long oval. This is connected with the 

 Eail's miraculous facility for passing rapidly through tangled 

 herbage. 



The following results of experiments and calculations made 

 on a freshly killed Little Grebe support the conclusions based on 



