KOTIWHENU 125 
by the Robin is incessant. It has ceased in any 
degree to be a tree-climber ; all its food is obtained 
amongst fern and sedge; the species has become 
purely a ground bird. The food of the Wren in 
the forest of the mainland, where it searches the 
boles and crevices of trees, must differ from the 
food gathered on Te Puka, and in yet greater 
degree from supplies found in the thickets of 
Kotiwhenu. The wings of the Wren are fully 
used on the mainland, partially used on Te Puka, 
almost useless on Kotiwhenu. With modified 
habits of exercise and modified food supply, 
structural changes and changes in plumage may 
reasonably be anticipated. Given time, the island 
Wren of Kotiwhenu becomes a form; given 
unlimited time, it becomes a species. 
Another difference betwixt birds known to me 
in other parts and those permanently resident on 
Kotiwhenu—autochthones—was in the size of the 
clutches. Non-migratory species such as the Bush 
Wren and the Saddleback lay two eggs only. 
The Robin, too, lays but a brace of eggs, though 
elsewhere the number is from four to five. The 
island therefore may be considered stocked to 
the limit of food supply of these three species. 
Migratory breeds, on the other hand, such as the 
Bellbird and Tui, birds that can come and go 
as they wish, lay the usual number of eggs. 
It may be that my premises are too circum- 
