that I mistrust thfe mpst harmless observations. 
On the xasxx ‘■behaviour other thah courtship and threat 
display I am more sure of myself but I think that interests 
you less. The threat and courtship seem to have gone quite 
a way on the road of ri tuallsa tion and although its simple 
enough to talk about recognising elements of attack and escape 
this doesn't seem to expla,in very much. At last I have got 
even Niko to agree that the tern s aren't as easy as he thought 
they might be but he always says "but think how much more you 
know about the tern's behaviour than anyone else". It's 
scant consolation when one compares it with your scheme in 
the BH gull or even Esther's ideas about the kittiwake. 
It Is very striking to me how much easier it is to understand 
much of the shag’s behaviour than the terns, because the 
shags move so slowly and their changes of mood are correspondingly 
slow. 
Niko thought it would be a good idea for Esther to publish 
a short paper based on the report for the Ibis or something and 
that is occupying her time at the moment. She would like it 
to be a bit more accurate in details than the report l 
’Ve've been very glad of the chance to see the two papers 
you sent to Pae in order to see which way your thoughts are 
turning since you left Oxford. I think that Pae has handed 
on to you some of my comments. Most of the things were more 
or less trivial but there were some more important objections 
One of the ones I feel most heated about is your discarding 
of displacement grass -pul Ting. If you had ever seen it you 
would see at once that the movement of depositing the material 
i 8 the nest building movement. And in any case when a gull has 
something in its beak which it wants to get rid of it shakes 
it off in a quite different way from what happens in grass 
nulling during fights. Incidentally Esther was reading Stelhbahe 
( 1 93 8) the other day and saw that he said that the gull 
treated the grass just as it would like to grab the opponent 
if it dared, so he clearly recognised the redirection element. 
I am sure you can't c-ompletely throw out all the displacemnt 
element In grass-pulling but I think that there is a<julte "simple" 
explanation of why the redirection grass pulling should be followed 
by sideways-building -- namely that the movement is stimulated 
by the presence of nest material in the beak. If there 
were any likelihood of some displacement activity occurring 
this would explain why it should be this particular one. 
Exactly the same argument would account for the observational** 
that when you crowd male sticklebacks the head-down threat goes 
into sand-digging, though here it is presumably the influenece of 
the posture which determines the displacement activity, I was 
very impressed by the link between certain activi ties A fin no 
sense in displacement situations) apparently as a result of the 
similarity in the posture. In these cjses I think I could conclude 
that the influence from the posture was a proprioreceotive one. 
Of course aj? some of the exapmles of "influence of tae 
environment" such as the stickleback example may be partly 
