COURTSHIP OF THE GREAT CRESTED GREBE. 515 
coition, as in most birds, but as excitants to some further act of 
courtship ; and this is always a mutual and also a self-exhausting 
one. ‘The excitants to coition are of a very special nature, and 
are symbols, rather than mere general excitants. 
Habit-Preening. (See p. 497.) 
This is very frequent, occurring in about half the bouts of 
shaking seen. The more excitement, the less preening, seems to 
be the rule ; long bouts may sometimes degenerate into practi- 
cally undiluted preening, the head simply being brought more or 
less up, but not shaken, between the “ preens.” It is always the 
hind end of the wings, I believe, which is raised and let fall by 
the beak. 
In some way there must be a strong association between 
preening and head-shaking in the Grebe, for solitary birds who 
were really preening themselves I have several times seen raise 
their heads, slightly bristle their crests, and give a rudimentary 
shake. Why or how the association has taken place is more 
difficult to say. I certainly believe that the action I call habit- 
preening has been derived from true preening, and has been 
ceremonialized in the process of becoming part of a courtship- 
action. For the present we must leave it at that, 
‘© Habit-Shaking.” 
That for some reason there is a very real association between 
shaking and preening is shown by the following facts. When 
actively engaged in real preening of themselves, the birds are 
often seen to lift their heads, give a rudimentary shake or two 
(without erecting ears or ruff) and then go back to business. 
This is generally seen when the bird is engaged in preening its 
hinder parts. We have observed it in autumn as well as in 
spring, and so it presumably takes place the year round ; there is 
thus obviously a real association between the preening and the 
shaking, and the shaking is not a mere release of simpler sexual 
energy. 
This is exactly the converse of what I have called ‘habit- 
preening,” and may therefore appropriately be styled “ habit- 
shaking.” 
There is thus a single association with a two-fold result. How 
it can possibly have arisen, or what purpose it can serve, remains 
to me at present an absolute mystery. I leave it as a puzzle to 
future bird-watchers and comparative psychologists. 
Fighting between Cocks. 
I saw very little of this beyond mere hostile expression (p. 521). 
Once, however, I saw two birds actually grappling: one was 
struggling half-submerged, while the other was more or less on 
top of it, and had hold of the feathers of the back of its opponent’s 
head. After some considerable splashing and struggling, they 
separated and swam apart. 
