THE BIRDS OF AUSTRALIA. 
to an instinctive habit. We are led to believe that instincts, so-called, are 
never-erring, but with the Cuckoos their methods are haphazard and full of 
error, hence one cannot attribute the peculiarities surrounding the nidification 
of Cuckoos as due to never-erring instincts. The mass of statistical data in 
my paper will once and for all time, I hope, settle the vexed question, generally 
accepted by casual observers, that Cuckoos select the nests of foster-parents 
in which to place their eggs that lay similar eggs to their own — that is, so 
far as Austrahan Cuckoos are concerned.” 
Had the statistics been published we might have been able to dissect 
them, so that probably different results might have been shown according to 
the different genera of the Cuckoos. Thus the extreme variation in the coloration 
of the eggs as applied to the European Cuckoo cannot be utilised in the genus 
Lamprococcyx, and while it might be true that the resemblance reached as 
high a percentage as 45 per cent, in the former, the infinitesimal percentage 
of Mattingley would be true of the latter : and as to the other points the like 
comment applies. 
In the Emu, Vol. XIV., p. 144, 1915, H. L. White stated clearly, without 
statistical data, conclusions which appeal to me and which seem confirmatory 
of the European results in plain language : “ For more than thirty years 
Cuckoo’s eggs have had a great attraction for me, and upon every possible 
occasion I have tried to add to my collection, which I now look upon as fairly 
complete, though there will always be what I call chance combinations to 
be added. It is evident to anyone who has given the matter a close study 
that the various species of Cuckoos have their favourite foster-parents, and 
that these are not very numerous ; outside of these favourites are what I 
term ‘ chance ’ or perhaps more properly, ‘ occasional,’ foster-parents, which 
are used now or then. There is no doubt in my mind that Australian Cuckoos 
which lay in open nests usually select as foster-parents those birds whose eggs 
nearly approach their own in coloration. A casual glance at my collection 
gives the impression that my theory is incorrect, as one’s gaze is met by many 
colours that do not harmonise, however uniform the general appearance may 
be. A visitor often exclaims, ‘ Oh, look here ! and here ! and here ! these 
differ altogether.’ ‘ Quite so,’ I admit, ‘ but please to remember that those 
you point out are occasional combinations only. Examine these dozen com- 
binations of “ favourites,” forming perhaps 90 per cent, of the foster-parents 
used by this particular Cuckoo. Do not they harmonise ? ’ The answer 
is invariably, ‘ Yes, of course they do ! ’ Taking the species of foster-parent 
as a whole, say those used by the Pallid Cuckoo {Cuculus pallidus), in 100 
species, it will probably be found that sixty of them do not harmonise. This 
does not disprove my theory in the proportion of six to four ; it simply proves 
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