Plumage of Herons 
colouring in the male is admired by the female ; 
and in this manner he sought to overcome some 
difficulties to his theory which certain birds 
presented. 
Writing of the heron family, he says :— 
“The young of the Ardea asha are white, the 
adults being slate-coloured; and not only the 
young, but the adults of the allied Buphus 
coromandus in their winter plumage are white, 
their colour changing into, a rich golden buff 
during the breeding season. It is incredible 
that the young of these two species, as well as 
of some other members of the same family, 
should have been specially rendered pure white, 
and thus made conspicuous to their enemies ; or 
that the adults of one of these two species should 
have been specially rendered white during the 
winter in a country which is never covered with 
snow. On the other hand, we have reason to 
believe that whiteness has been gained by many 
birds as a sexual ornament. We may therefore 
conclude that an early progenitor of the Ardea 
asha and the Bupfhus acquired a white plumage 
for nuptial purposes, and transmitted this colour 
to their young; so that the young and the old 
became white like certain existing egrets, the 
whiteness having afterwards been retained by 
the young whilst exchanged by the adults for 
more strongly pronounced tints. But if we 
could look still further backwards in time to 
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