KOTIWHENU 121 
—islands which are dunghills, and which pro- 
duce insect food as from a teeming midden. 
Thus amongst the Bellbirds of these southern 
latitudes an alternative form of nest structure is 
gradually coming into existence. When all Bell- 
birds breed in holes we shall then term the habit 
instinctive, and so it will be if instinct is subli- 
mated common-sense. Of the nesting habit of 
the southern Robin on the mainland I know but 
little, but all Robin’s nests discovered on Koti- 
whenu were built in shelter of one sort or another, 
beneath cornices of ancient dead masses of fern 
frond, beneath projecting timber, spots in fact 
where of necessity nests had to be built to ensure 
the preservation of the race. 
Differences between North Island species, such 
as the Pied Tit, the Pied Fantail, the Blue-wattled 
Crow, and South Island species, such as the 
Yellow-breasted Tit, the Black Fantail, and the 
Orange-Wattled Crow, are insignificant. It is 
impossible now to discover how these minute 
variations have come about—why, for instance, 
the Tit of the North should be white-breasted, 
whilst the Tit of the South should be pale yellow 
or pale carmine? Probably some small climatic 
modification has given rise to other modifications, 
one of which has at last affected the coloration 
of the plumage, and thus made visible to the eye 
a change previously existent indeed, but hitherto 
