ii6 ESSAYS OF A BIOLOGIST 



secrets to betray. If the sitting bird wishes to leave 

 the nest, and the other does not return, it flies off, 

 after covering the eggs with weed, in search of its 

 mate ; it is common in the breeding season to see a 

 Grebe in the 'search-attitude,' with neck stretched 

 up and slightly forward and ear-tufts erected, emitting 

 a special and far-carrying call. When this call is 

 recognized and answered, the two birds do nothing so 

 simple as to fly or swim to each other, but a special 

 and obviously exciting ceremony is gone through. 

 The bird that has been searched for and found puts 

 itself into a very beautiful attitude, with wings half- 

 spread and set at right angles to the body, ruff erected 

 circularly, and head drawn back upon the shoulders, 

 so that nothing is visible but the brilliant rosette of 

 the spread ruff in the centre of the screen of wings, 

 each wing showing a broad bar of brilliant white on 

 its dusk-grey surface. In this position it swings rest- 

 lessly back and forth in small arcs, facing towards its 

 mate. The discoverer meanwhile has dived ; but, 

 swimming immediately below the surfece of the water, 

 its progress can be traced by the arrowy ripple it raises. 

 Now and again it lifts its head and neck above the water, 

 periscope-wise, to assure itself of its direction, and 

 resumes its subaqueous course. Nor does it rise just 

 in front of the other bird ; but swims under and just 

 beyond, and, as its mate swings round to the new 

 orientation, emerges in a really extraordinary attitude. 

 At the last it must have dived a little deeper ; for now 



