The Making of Species 
Wallace’s view that the dull plumage of the 
hen bird is due to her greater need of protection 
is based on the assumption that the hen bird alone 
takes part in incubation. 
Is this assumption a correct one? 
It certainly is not in all cases. As D. Dewar 
has stated in Bzrds of the Plains, the showy 
white cock Paradise Fly-catcher (Zerpszphone 
paradisz) sits in broad daylight on the open nest 
quite as much as the hen does. And this may 
prove to be true of many other species of 
birds. Again, the cocks of the various species 
of Indian sunbirds are brightly coloured while 
the hens are dull brown. In these species the 
hen alone sits on the eggs, but, as the nest is 
well covered-in, the hen might display all the 
colours of the rainbow without being visible 
to passing birds. Moreover, as D. Dewar 
pointed out in a paper read before the Royal 
Society of Arts (Journal, vol. lvii., p. 104), 
although, in most species of Indian dove, the 
sexes show little or no dissimilarity, there is one 
species (nopopelia tranquebarica) which ex- 
hibits considerable sexual dimorphism. But the 
nesting habits of this peculiar species are in 
all respects similar to those of the other species 
of dove. Why then the marked dissimilarity of 
the sexes? 
Another objection to the theory of Wallace is 
that urged by J. T. Cunningham (Archiv fir 
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