BRITISH WARBLERS 
erecting his feathers and singing continuously. When one 
female temporarily disappears, he immediately commences to 
pay attention to the remaining one, precipitating himself 
towards her after his manner, and discontinuing only on the 
return of the other female. A struggle of this kind sometimes 
results in the disappearance of both the females, the one 
having apparently driven the other away, the male being 
thus left alone unmated for perhaps another ten days. 
The period between the time when a female arrives in 
a territory of a given male, and the time when the first egg 
is laid is a varying one. Though commonly referred to as the 
period of courtship, it is probably one of fertilisation and 
development only. Before finally deciding one way or the 
other, it is above all things necessary to know when the first 
act of coition takes place, whether a single act suffices for the 
fertilisation of all the eggs, or each ege requires separate 
fertilisation. Now of all this we have little enough know- 
ledge even of our domestic creatures. How, then, can it be 
expected that we should obtain sufficient evidence to be of 
value in the case of wild ones? With the larger species it 
might, by very close study, be possible to obtain this, but as 
far as the smaller birds, ever moving and flitting from bush 
to bush, are concerned, it will always remain a difficult matter 
to acquire the necessary knowledge. Yet without this know- 
ledge a complete understanding of the numerous diverse 
activities occurring at this period is impossible. But we can 
still attempt to understand them in part, and in order to do 
this we must utilise the only other means at our disposal, 
namely, deduction from the general behaviour of both sexes. 
And it is just because, speaking generally, there is a gradual 
diminution of excitement, which would naturally be the result 
of fertilisation and not an increase, or at any rate a continuity 
of the excitement, which would result from a prolonged court- 
ship, that I am led to believe that the period zs one of fertilis- 
ation and not of courtship. By copying from my notes a 
brief description of the behaviour of a pair in the morning 
10 
