258 MR. JULIAN S. HUXLEY ON 
Activities of a Particular Mated Pair. 
T will now proceed to describe in some detail the actions of one pair which- 
I had under close observation for a few days, since I believe that in this wajr 
a fuller insight is gained by the reader (as it certainly is by the observer at 
the time) into the psychology of the birds. 
On a small tarn about a mile from camp a single Diver was observed on 
June 30. The tarn was then only partially thawed, and nest-building was 
out of the question. It would appear, however, that the birds had already 
" staked out a claim " to this special nesting territory, as is known to be done 
by many if not all monogamous birds before actual nest-building begins (see- 
E. Howard, '20). A single bird was again observed here on July 4 ; it was- 
restless and remained on the tarn for a long time ; nest-building had almost 
certainly begun, as the event showed. On July 5 both birds of the pair 
were seen on the tarn, and one visited the spot where the nest afterwards 
proved to be. It only stayed half a minute or less, and then returned to the 
water. The birds were continually giving a mewing call, very similar to 
that given by solitary birds on the water, or by sitting birds when man or a 
Skua threatens danger. The call as given on this occasion, however, I record 
as " louder, longer, and more emotional than when given by a solitary bird." 
Usually the two birds would howl almost, but not quite, simultaneously. 
There was certainly some sexual significance attaching to this "duet- 
howling." 
At one moment the tj'pical " roll-growl " was given. This I take as 
proof that a snake-ceremony occurred, although the birds were unfortunately 
invisible below the high bank. On my approach to pitch my observation 
tent, the birds rose together and made off. I take it as certain that no egg 
was as yet laid, since, once this has happened, the nest is sat on almost con- 
tinuously to prevent Skuas stealing the egg. 
Next day (July 6) I spent about 9 hours at the tarn. It was noticed that- 
whenever the liowl or mewing note was given, the neck was stretched out 
nearly or quite parallel with the water. This was confirmed on many sub- 
sequent occasions. The action seems to be inseparable from the particular 
note. It is probable that it renders the bird less conspicuous (see Van Oordt 
and Huxley, he. cit.). The note was given repeatedly by the solitary bird 
(female) that was there at intervals from noon to 3 p.m. Occasionally the 
bill would be dipped as in sexual excitement. At one time she indulged in 
what were obviously practice dives, just in and out, emerging two to four 
lengths away. This was repeated five times in quick succession. 
Shortly after, the male arrived. The female speedily joined him, and the 
pair swam towards me, the female leading, with bill slightly open. When 
close to the bank, the female suddenly performed a remarkable action, 
obviously of a sexually stimulating nature. She stretched her neck forwards 
at an angle of perhaps 30° with the horizontal, the head and beak also 
