- 4 - 
are similar. This seems to he to he a severe limitation in 
trying to recognise the homologues of various movements, perhaps 
more severe than in comparing morphological characteristics. 
But i all this argumentation rings a hell with me and. I feel 
sure I have opened, my heart to you on these matters before. 
Gould you perhaps let me know what you think about all this ? 
Have you in fact encountered these difficulties in you studies 
or are the gulls sufficently similar ? There is again the 
difficulty with the Kittiwake which, to judge from the few species 
of gulls with which we are here familiar is very different from 
either the Herring Gull or the Black-headed - much more so 
in our opinion than these two species are from each other, though 
I note with interest that you put Rissa into the "hooded gull 
sub-group" rather than the "large gull one". The Kittiwake 
seems sufficiently different in the form of its movements for 
us to have great reluctance to say what the Long Call is in this 
species. Niko says always it is the ki t tiwake-call but admits 
there is really no bettscer reason for picking on this than 
there is to say that the Moan is the long call. Mx In 
comparing a greater range of gull species you rnustv have 
found some useful criteria is deciding what the long call is, 
can you disgorge this information ? 
By the way before leaving the matter of systematics I 
note that you feel sab ini is more difficult to place than 
many of the other species. Is this on morphological grounds 
or behaviour ? Ie have seen a fragment of display of this 
species on a film of Peterson called Birds of America which 
has be-en shown here by James Fisher. There may well be more 
on the Sabine's gull in the original, I don't know. Anyway 
from what we saw the bird seemed very like our memory of a 
black-headed. 5 Have you seen the film ? Or the bird ? 
When you get my report on the gull and tern conference you 
will see that Voous had already suggested to me some of the 
points about the systematics of terns which you mention, 
namely the inclusion of Hydroprogne with the other crested terns 
and the intermediate position of the Roseate between the 
Thalasseus terns and the typical S te rna . What sort of evidence 
does one use in classifying the terns ? There seems so little 
morphological difference between the adults - at any rate of tne 
typical Sterna. Kow do you reconcile Murphy ( 1933) on the pan- 
Antarctic terns with the evidence of Clay (1949?) ana Kullenberg? 
How do you d ecide whit Is convergence and what is genuine 
relationship ? 
But I have driften far from my intended path. I was giioing 
some idea of the similarities of the calls of other species to 
those of the Arctic. The Roseate has what I have called 
the Harsh Call, which is utterly un-transcribable . It is 
a sort of hawk, as if the bird were about tb spit, i.txia 
From pure form alone I couldn' t.. place it but it comes 
in the same situations as the 'Iceeyair of the Arctic and 
I have once seen wing-raising which is so typical of this 
call in the Arctic but which doesn't oc curMn^any other calU 
In the Sandwich there is no doubt of the similarity of the"waaaa" 
