NARROW-BILLED BRONZE CUCKOO. 
of fact probably all three combine to distinguish the subspecies. Thus, the 
colouring of the tail has been regarded as a specific character, and such it is, 
but it is very variable according to sex and age as well as the individual. Thus, 
two males from the same locality, apparently both adult, may show very great 
differences in the amount of rufous on the base of the tail. Again, a male and 
female generally show decided differences in tail coloration from the same 
locality, while the immature also shows differences. 
Now, from another locality the differences here seen may be constantly 
fixed and of geographic importance, as the much more rufous condition ascribed 
to immature and females in the south may be a constant feature of northern 
males. As the bird is a more or less permanent resident wherever it occurs, it 
is suggested that full series will cause the admission of many subspecies, and, 
moreover, when such are independently studied many features of interest may 
be revealed which would be lost sight of by a lumping method. 
At present I cannot distinguish more than I have already admitted, mainly 
because the series from a given locality generally show too many immatures in 
proportion to the adults, and while these are of extreme value my studies lead me 
to use them conservatively. Again, odd specimens from such locahties as Cape 
York and Melville Island suggest a movement of some sort, but do not give 
much clue. It is possible that variation in the same locality may be due to 
unknown movements, while study of extra-limital series would be of great 
interest. The under-surface development needs further study than has been 
given it ; the immature nestling is unbarred, then few bars appear, mostly 
on the sides of the body ; and generally the adult shows few far apart bars, the 
centre remaining unbarred. Some specimens, however, show narrow bars 
more closely set and almost extending across the abdomen. This variation 
has not been fixed with geographical significance, yet in the allied genus it is 
distinctive of distinct species. The throat striping as distinct from barring 
is characteristic of the genus. 
A peculiar feature in connection with age development will be dealt with 
under the species L, russatus, a form I referred to this genus, before good series 
explained the plumage changes and proved the present genus must depend 
on structural characters more than colour variation. 
347 
