60 THE SCOTTISH NATURALIST 



plate was expanded, so much so as to be^'isible from behind, 

 projecting on each side of the head. The male advanced to 

 the stranger, calling repeatedly, with head depressed almost 

 level with the water and bill slightly upturned, but the 

 female showed little interest and mounted on the bank of 

 the pond. The male retired to the island for a few moments 

 and then sallied forth once more, coming over to the side of 

 the pond ; but, disappointed with the inattention of the other, 

 returned towards the island calling at intervals and looking 

 back. At last it induced the other, which I took to be the 

 female, to return to the water ; but when the male approached, 

 calling excitedly, she again retired to land. After a further 

 swimming to and fro, the male at last induced the female 

 to join him at the island. A little later the two were 

 cossetting or "nibbling" one another about the head, and 

 stroking each other's plumage. Now and again, when the 

 two were feeding apart, one (which, is not certain) would 

 give the loud ringing call, and the other would hurry to it, 

 the two meeting with depressed head and uptilted bill, and 

 they would indulge in further love-making. At other times, 

 instead of stroking or nibbling, the two birds would stop, 

 facing one another, and remain for five to ten seconds with 

 neck arched and bill half immersed in the water. Whether 

 any sound was uttered has not been determined. The 

 enlargement of the frontal plate has only been seen during 

 the excitement of courtship. In early spring, individuals 

 have been seen to strike the courting attitude and give 

 the ringing call when no female was on the pond. 



Nest-building does not take place immediately after the 

 pair has settled down, two to three weeks having passed in 

 some cases before any attempt has been made to build. 

 As to the actual date of nesting, the first week of May has 

 been chosen in three out of the six nests seen, once the first 

 week of June, once the first week of July, and once, quite 

 exceptionally, nest-building was in progress on 16th March 

 (in 191 3), and incubation was begun the following week. 

 Whether both birds work in building the nest is not clear, 

 but the male, even after the female has begun to sit, seems 

 to be interested in the further supply of nesting material. 



